Hydroxyapatite Nanoparticles in Drug Delivery: Physicochemistry and Applications

Impact of hydroxyapatite nanoparticles on the cellular processes of stem cells derived from dental tissue sources

Hydroxyapatite nanoparticle (HANPs) utilization has recently been notable in bone tissue engineering. This surge owes itself to the biocompatibility of HANPs and their striking resemblance to the minerals found in natural bone. Furthermore, dental pulp-derived stem cells (DPSCs) have garnered attention due to their remarkable differentiation potential into multilineages, thus positioning them as a pivotal cell reservoir for regenerative medicine. This study aims to investigate the impact of HANPs on DPSCs cellular processes. The HANPs have been synthesized using the wet chemical precipitation method followed by freeze-drying and characterization using dynamic light scattering (DLS) and transmission electron microscopy (TEM). The size of HANPs was reported to be in the range of 55-67 nm. Our dataset divulges that DPSCs can endure concentrations of HANPs up to ≤ 0.81 mg/mL without incurring any conspicuous alterations in their morphology or the pace of proliferation. Furthermore, the self-renewal potency of HANPs was upheld at concentrations ≤ 0.20 mg/mL. Flow cytometric analysis affirms a significant divergence in cell distribution across all cell cycle phases in DPSCs treated with 0.81 mg/mL HANPs. Intriguingly, no variance surfaced in the migratory capacity of DPSCs exposed to HANPs of ≤ 0.40 mg/mL. For osteogenic differentiation, HANPs at concentrations of ≤ 0.40 mg/mL demonstrated the aptitude to incite osteogenic differentiation within DPSCs, facilitating the formation of calcium deposits. In conclusion, combining HANPs and DPSCs shows promise for restoring damaged hard tissues, like bone and teeth, and enhancing regenerative therapies.

Quantitative Analysis of Salmon Calcitonin Hydroxyapatite Nanoparticle Permeation to substantiate Non-Invasive Bone Targeting via Sublingual Delivery

We earlier reported comparable efficacy in bone parameters of sublingually administered salmon calcitonin hydroxyapatite nanoparticles (SCT-HAP-NPs) compared to the subcutaneous injection, in the ovariectomy rat model, despite a bioavailability of barely ~ 15%. We ascribed this intriguing finding to targeted bone delivery, facilitated by translocation of significant quantity of intact NP into systemic circulation. In the present study we track the translocation of FITC-SCT-HAP-NPs (~ 100 nm) across porcine sublingual mucosa using the Franz diffusion cell to validate our hypothesis. Confocal Laser Scanning microscopy (CLSM) established that SCT-HAP-NPs permeated into the deeper layers of sublingual porcine mucosal tissue. We confirmed the nanoparticles were present in the receptor medium of the Franz diffusion cell by DLS and TEM. We also demonstrate for the first time quantification of the NPs (%) translocated across the porcine mucosa, using the Amnis Image StreamX Mk II imaging flow cytometer. Computation revealed transport of ~ 60% of the FITC-SCT-HAP-NPs across mucosa in 2 h, substantiated that high NP concentrations could reach systemic circulation. Such high NP concentration in systemic circulation coupled with the small size (~ 100 nm) and the high bone affinity of HAP, validate our hypothesis of targeted bone delivery following sublingual administration. Furthermore, quantification of translocated NPs, which we demonstrate for the first time, would permit rational development of optimal targeted nanoparticulate carriers for delivery by noninvasive routes.

pH-Responsive Near Infrared Light Triggered Hydroxyapatite Nanoparticles for Targeted Photothermal Cancer Therapy

Photothermal therapy (PTT) has emerged as an effective cancer treatment strategy, which utilizes photothermal agents that accumulate at tumor sites and induce localized hyperthermia when irradiated. Near-infrared II (NIR II) fluorophores, such as the polymethine cyanine-based photothermal dye IR1061, exhibit higher temporal resolution and better tissue penetration, thereby making them promising candidates for PTT. However, challenges such as the low water solubility and in vivo short circulation times of these dyes limit their biological applications. To address these issues, we have developed a biocompatible and biodegradable delivery system in which IR1061 is encapsulated within lipid-coated hydroxyapatite nanoparticles (LHAPNIRs). The lipid shell is composed of DPPC/cholesterol/DSPE-PEG to retain the encapsulated dye and prevent serum protein adsorption and macrophage recognition, which would otherwise that hinder tumor targeting. Finally, the coat is functionalized with an acidity-triggered rational membrane (ATRAM) peptide for efficient and specific internalization into tumor cells in the mildly acidic microenvironment characteristic of tumors. The nanoparticles facilitated real-time thermal imaging and showed potent NIR-light triggered anticancer activity in vitro and in vivo, with no noticeable toxicity to healthy tissue. Our results demonstrate that ATRAM-LHAPNIRs (ALHAPNIRs) combine potent PTT and robust diagnostic imaging capabilities.

Synthesis and the impact of hydroxyapatite nanoparticles on the viability and activity of rhizobacteria

Preserving the viability of rhizobacteria during plant application poses a significant challenge when utilizing rhizobacteria as biofertilizers, especially under adverse environmental conditions. Therefore, the selection of a suitable carrier material for rhizobacteria plays a crucial role in ensuring the sustained viability of these microorganisms. Nanomaterials, particularly nanohydroxyapatite (nHA), have garnered attention for sustaining rhizobacterial viability, high loading capacity, high biodegradability, and biocompatibility, which facilitate microbial interactions. In this study, nHA was synthesized using a hydrothermal method and used as a carrier for two rhizobacteria strains (Pd and Tb). The structural and morphological properties of nHA were examined through XRD and scanning electron microscopy analyses. Rhizobacteria were encapsulated within the carrier material, and their viability was evaluated using the total plate count method. Following their immobilization on nHA, the phosphate-solubilizing capacity of rhizobacteria was evaluated using Pikovskaya's medium. A nitrogen-free bromothymol medium was utilized to qualitatively assess the nitrogen-fixing ability of rhizobacteria. Furthermore, rhizobacteria were identified using 16S rRNA gene sequencing, followed by analysis to construct a phylogenetic tree. nHA was found to meet the required quality criteria, exhibiting a spherical morphology with an average particle size of 68 nm and a porosity of 54.78%. The nHA carrier demonstrated favorable physical attributes to sustaining rhizobacterial viability with pH 8.95 and an electrical conductivity of 55.4 μS/cm. Rhizobacteria loaded onto the nHA carrier maintained comparable viability to those without carriers. The highest viability of the rhizobacterial strains Pd and Tb loaded onto the nHA carrier was observed on the seventh day after inoculation, measuring at 2.480 × 107 and 1.040 × 107 CFU/mL, respectively. The qualitative tests of nHA as rhizobacterial carrier demonstrated that rhizobacteria retained their ability to solubilize phosphate and fix nitrogen. Furthermore, both rhizobacteria have been identified. Pd rhizobacterium was identified with complete match to Brevundimonas olei strain Prd2. Similarly, Tb rhizobacterium showed 100% similarity to Bacillus altitudinis strain NPB34b. Based on this reseach, nanohydroxyapatite could be the potential carrier to protect rhizobacteria from external stressors and to maintain their viability over the long term. These findings indicate the potential of a nanohydroxyapatite-rhizobacteria system as a promising environmentally friendly fertilizer.

Comparative study of nanohydroxyapatite-emdogain effects on apical papilla stem cell survival and differentiation

BACKGROUND

The study was designed to explore the enhanced impact of nano-hydroxyapatite and emdogain on the survival and osteogenic/odontogenic differentiation of human stem cells isolated from the apical papilla (hSCAPs).

MATERIALS AND METHODS

In this in vitro trial, hSCAPS obtained from intact impacted immature third molars were confirmed to have characteristic cell surface markers, then exposed to nanohydroxyapatite, emdogain, and nanohydroxyapatite coated with emdogain for durations of 1-3 days. The survival of apical papilla stem cells was measured using a methyl thiazolyl tetrazolium assay. The quantitative reverse transcription polymerase chain reaction, alkaline phosphatase activity (ALP) and Alizarin red staining were used to evaluate osteogenic-odontogenic differentiation. Analysis of the data was done using one-way ANOVA, t-test, and Mann-Whitney test (α = 0.05).

RESULTS

At 1-3 days, emdogain exhibited no significant impact on the survival of human stem cells from the apical papilla. In contrast, nanohydroxyapatite (α > 0.05) and nanohydroxyapatite coated with emdogain demonstrated a notable reduction in cell survival compared to the control group (α < 0.05). The expression of dentin sialophosphoprotein, dentin matrix protein 1, and bone sialoprotein genes demonstrated a notable increase in the group treated with nanohydroxyapatite coated with emdogain compared to the other groups (α < 0.05), and furthermore, this group exhibited more pronounced mineralized nodules than the other experimental groups.

CONCLUSION

In contrast to nanohydroxyapatite, Emdogain did not demonstrate a detrimental effect on the survival of hSCAPs. Nanohydroxyapatite, emdogain, and nanohydroxyapatite coated with emdogain increased osteogenic/odontogenic differentiation of hSCAPs.

Fabrication of biocidal materials based on the molecular interactions of tetracycline and quercetin with hydroxyapatite via In Silico- and In vitro approaches

Synthetic hydroxyapatite (HA) materials with antibacterial and biocompatible properties have potential for biomedical applications. The application of various computational methods in silica is highly relevant for the optimal development of modern materials. In this work, we used molecular docking to determine the binding constants of tetracycline (TET) and quercetin (QUE) with hydroxyapatite and compared them to experimental data of the adsorption of tetracycline (TET) and quercetin (QUE) on the HA surface. The experimental adsorption study was performed via the UV-VIS method. The fabricated biocidal powders were characterized via X-ray powder diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). The electrical charge of the HA particle surface was determined via zeta potential measurements. The molecular docking method was used to predict the binding affinities of TET and QUE for HA. We also performed molecular docking studies to predict the binding affinity of TET and QUE for HA. These affinities correlate with the experimental binding constants, suggesting that molecular docking is a good tool for material property prediction. In addition, the antimicrobial activity of the HA/TET and HA/QUE powders was determined against 2 g-positive bacterial strains: S. aureus and E. faecalis. The obtained HA powders were evaluated for biocompatibility in vitro with the myoblast cell line C2C12.

3D scaffold of hydroxyapatite/β tricalcium phosphate from mussel shells: Synthesis, characterization and cytotoxicity

Bone tissue substitutes are increasing in importance. Hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) act as a cell matrix and improve its mechanical properties. One of their raw materials is marine-origin by-products.

OBJECTIVES

To synthesize, characterize, and evaluate the cellular cytotoxicity of a 3D biomaterial based on HA and β-TCP from mussel shells.

METHODS

We prepared pellets with 150, 200, and 250 mg and evaluated them through sintering, XRD, FTIR, ICP-OES, Scanning Electron Microscopic (SEM), and immunocytochemical tests. The Alamar Blue method was applied to the Balb-T3T cell line within 72 h to evaluate cytotoxicity.

RESULTS

Our biomaterials presented a smooth surface with slight irregularity and porosities presenting different diameters and morphologies and showed chemical, morphological, and ultrastructural similarity to bone hydroxyapatite, mainly the 150 and 200 mg pellets.

SIGNIFICANCE

We produced promising HA/β-TCP bioceramics with characteristics that allowed cell culture, promoting adhesion, spreading, and proliferation.

Development and Optimization of Nano-Hydroxyapatite Encapsulating Tocotrienol-Rich Fraction Formulation Using Response Surface Methodology

Background/Objective: The tocotrienol-rich fraction (TRF) is a lipid-soluble vitamin that has good antioxidant and anti-inflammatory properties. The TRF is widely studied as a potential treatment for various diseases, including bone diseases. However, its application is limited due to its poor oral bioavailability profile, warranting an innovative approach to overcome its pharmacokinetic limitations. Recently, the nano-hydroxyapatite (nHA) has been investigated as a drug delivery vehicle for various drugs and active compounds owing to its excellent biocompatibility, biodegradability, and osteogenic properties. The nHA is also a well-known biomaterial which has chemical and structural similarities to bone minerals. Hence, we aim to explore the use of the nHA as a potential nanocarrier for the TRF. Methods: In this study, we develop and optimize the formulation of an nHA-encapsulating TRF (nHA/TRF) by employing the response surface methodology (RSM). Results: RSM outcomes reveal that the mass of the nHA, the concentration of the TRF, and the incubation time have a significant effect on the particle size, zeta potential, and encapsulation efficiency of the nHA/TRF. The outcomes for the optimized formulation are not significantly different from the predicted RSM outcomes. The optimized nHA/TRF formulation is freeze-dried and results in an average particle size of ~270 nm, a negative zeta potential value of ~-20 mV, a polydispersity index of <0.4, and an encapsulation efficiency of ~18.1%. Transmission electron microscopy (TEM) shows that the freeze-dried nHA/TRF has a spherical structure. Conclusions: Taken together, the above findings indicate that the nHA may be established as a nanocarrier for efficient delivery of the TRF, as demonstrated by the promising physical properties.

Preparation and characterization of highly crystalline hydroxyapatite (HAp) from the scales of an anadromous fish (Tenualosa ilisha): a comparative study with the freshwater fish scale (Labeo rohita) derived HAp

Waste generation from fish processing sectors has become a significant environmental concern. This issue is exacerbated in countries with high aquaculture production and inefficient fish scale (FS) utilization. This study prepared and compared highly crystalline hydroxyapatite (HAp) from the FS of an anadromous fish, Tenualosa ilisha (I-HAp), and a freshwater fish, Labeo rohita (R-HAp). Acid-alkali treatment followed by high-temperature calcination was employed for HAp synthesis. XRD analysis indicated a monoclinic crystal structure for I-HAp and a hexagonal structure for R-HAp, with both containing β-TCP as a secondary phase. Rietveld refinement quantified β-TCP at 8% for I-HAp and 7.2% for R-HAp. Crystallite size of the samples was estimated by various methods (Scherrer's method, Scherrer equation average method, linear straight-line method, straight line passing the origin method, Monshi-Scherrer method, Halder-Wagner method, Williamson-Hall method, and size-strain plot method), consistently indicating microcrystalline HAp. FESEM and TEM analyses revealed larger particle sizes for I-HAp, confirmed by DLS measurements. Surface elemental analysis by XPS confirmed the presence of Na and Mg as impurities along with the elements of the HAp structure. FTIR and Raman spectroscopy identified expected functional groups, while EDX determined elemental composition. Both HAp samples exhibited bioactivity through apatite layer formation in simulated body fluid. Furthermore, the combined results of the cell viability and hemocompatibility studies indicate the biocompatibility of the prepared samples.

Calcium Phosphate Nanoparticles as Carriers of Low and High Molecular Weight Compounds

Nanoparticles could improve the bioavailability of active agents of various natures to human, animal, and plant tissues. In this work, we compared two methods on the synthesis of calcium phosphate nanoparticles (CaPs), differed by the synthesis temperature, pH, and concentration of the stabilizing agent, and explored the possibilities of incorporation of a low-molecular-weight peptide analogue enalaprilat, the enzyme superoxide dismutase 1 (SOD1), as well as DNA and dsRNA into these particles, by coprecipitation and sorption. CaPs obtained with and without cooling demonstrated the highest inclusion efficiency for enalaprilat upon coprecipitation: 250 ± 10 μg/mg of CaPs and 340 ± 30 μg/mg of CaPs, respectively. Enalaprilat sorption on the preliminarily formed CaPs was much less effective. SOD1 was only able to coprecipitate with CaPs upon cooling, with SOD1 loading 6.6 ± 2 μg/mg of CaPs. For the incorporation of DNA, the superiority of the sorption method was demonstrated, allowing loading of up to 88 μg/mg of CaPs. The ability of CaPs to incorporate dsRNa by sorption was also demonstrated by electrophoresis and atomic force microscopy. These results could have important implications for the development of the roots for incorporating substances of different natures into CaPs for agricultural and medical applications.

Hydroxyapatite Nanocoatings Deposited by Means of Resonant Matrix-Assisted Pulsed Laser Evaporation

Hydroxyapatite (HAp) is one of the most widely studied materials for utilization in the development of artificial implants. Research is mainly aimed at the production and modification of HAp coatings for simplification of the deposition process, cost reduction, and increase in biocompatibility. In this paper, the authors deposited HAp synthetic microparticles by means of matrix-assisted pulsed laser evaporation (MAPLE) on Ti6Al4V alloy plate substrates and obtained uniform HAp coatings without further treatment or modifications. The authors utilized a tunable pulsed laser to adjust its wavelength to the selected solvents, in order to optimize the process for deposition speed and quality. The following solvents were used as matrices: deionized water, isopropyl alcohol, and a 3:2 mixture of isopropanol:acetonitrile. Obtained coatings were examined by means of scanning electron microscopy, Raman spectroscopy, X-ray diffraction, and profilometry in order to evaluate coating quality, uniformity, and structural integrity. MAPLE deposition allowed the acquisition of approx. 200 nm thick coatings for water and isopropanol matrices and approx. 320 nm for isopropanol:acetonitrile matrix, which indicates an increase in deposition rate by 37%. The obtained coatings meet requirements for further biocompatibility testing, material modification, and composite synthesis.

Effect of Hydroxyapatite Nanoparticle Crystallinity and Colloidal Stability on Cytotoxicity

Hydroxyapatite nanoparticles (nHA) have gained attention as potential intracellular drug delivery vehicles due to their high binding affinity for various biomolecules and pH-dependent solubility. Yet, the dependence of nHA cytocompatibility on their physicochemical properties remains unclear since numerous studies have revealed starkly contrasting results. These discrepancies may be attributed to differences in size, shape, crystallinity, and aggregation state of nHA, which complicates fundamental understanding of the factors driving nHA cytotoxicity. Here, we hypothesize that nHA cytotoxicity is primarily driven by intracellular calcium levels following the internalization of nHA nanoparticles. By investigating the cytotoxicity of spherical nHA with different crystallinity and dispersity, we find that both lower crystallinity and increased agglomeration of nHA raise cytotoxicity, with nanoparticle agglomeration being the more dominant factor. We show that the internalization of nHA enhances intracellular calcium levels and increases the production of reactive oxygen species (ROS). However, only subtle changes in intracellular calcium are observed, and their physiological relevance remains to be confirmed. In conclusion, we show that nHA agglomeration enhances ROS production and the associated cytotoxicity. These findings provide important guidelines for the future design of nHA-containing formulations for biomedical applications, implying that nHA crystallinity and especially agglomeration should be carefully controlled to optimize biocompatibility and therapeutic efficacy.

Characterization and preparation of food-derived peptides on improving osteoporosis: A review

Osteoporosis is a systemic bone disease characterized by reduced bone mass and deterioration of the microstructure of bone tissue, leading to an increased risk of fragility fractures and affecting human health worldwide. Food-derived peptides are widely used in functional foods due to their low toxicity, ease of digestion and absorption, and potential to improve osteoporosis. This review summarized and discussed methods of diagnosing osteoporosis, treatment approaches, specific peptides as alternatives to conventional drugs, and the laboratory preparation and identification methods of peptides. It was found that peptides interacting with RGD (arginine-glycine-aspartic acid)-binding active sites in integrin could alleviate osteoporosis, analyzed the interaction sites between these osteogenic peptides and integrin, and further discussed their effects on improving osteoporosis. These may provide new insights for rapid screening of osteogenic peptides, and provide a theoretical basis for their application in bone materials and functional foods.

Recent development and applications of electrodeposition biocoatings on medical titanium for bone repair

Bioactive coatings play a crucial role in enhancing the osseointegration of titanium implants for bone repair. Electrodeposition offers a versatile and efficient technique to deposit uniform coatings onto titanium surfaces, endowing implants with antibacterial properties, controlled drug release, enhanced osteoblast adhesion, and even smart responsiveness. This review summarizes the recent advancements in bioactive coatings for titanium implants used in bone repair, focusing on various electrodeposition strategies based on material-structure synergy. Firstly, it outlines different titanium implant materials and bioactive coating materials suitable for bone repair. Then, it introduces various electrodeposition methods, including electrophoretic deposition, anodization, micro-arc oxidation, electrochemical etching, electrochemical polymerization, and electrochemical deposition, discussing their applications in antibacterial, osteogenic, drug delivery, and smart responsiveness. Finally, it discusses the challenges encountered in the electrodeposition of coatings for titanium implants in bone repair and potential solutions.

Synthesis and characterization of different nano-hydroxyapatites and their impact on dental enamel following topical application for dental bleaching

OBJECTIVE

This study aims to synthesize, characterize, and assess the penetration of hydrogen peroxide (HP), color change (CC), and surface morphology changes after the application of two distinct nano-hydroxyapatite (nano-HAp).

METHODS

Two nano-HAp were previously synthesized by co-precipitation: one with rod-shaped particles (RS) and the other with spherical-shaped particles (SS). The surface charge of the nano-HAp particles was determined at varying pH levels and characterized by X-ray diffraction patterns and Fourier transform infrared spectroscopy. The morphology of the samples was assessed using scanning electron microscopy (SEM). The nano-HAp particles were applied before the dental bleaching procedure. Forty teeth were divided into four groups (n = 10) according to the bleaching treatment: no treatment, bleaching with 35 % HP only, RS application and bleaching with 35 % HP, and SS application and bleaching with 35 % HP. HP concentration (µg mL-1) was measured using UV-Vis, while CC was evaluated with a digital spectrophotometer (ΔEab, ΔE00 and WID). Additionally, four teeth from each group were selected for SEM analysis. Statistical analysis encompassed one-way ANOVA, Tukey's, and Dunnet's tests.

RESULTS

RS and SS were successfully synthesized by coprecipitation, primarily differing in pH during synthesis. Both variations of nano-HAp morphology significantly reduced HP diffusion into the pulp chamber (p < 0.001). Regarding enamel morphology, groups analyzed post dental bleaching exhibited greater HAp deposition on the enamel surface. Notably, this deposition did not impede CC.

SIGNIFICANCE

The utilization of different nano-HAp morphologies prior to dental bleaching appears to be a promising strategy for mitigating adverse effects associated with dental bleaching procedures.

Hybrid Hydroxyapatite-Metal Complex Materials Derived from Amino Acids and Nucleobases

Calcium phosphates (CaPs) and their substituted derivatives encompass a large number of compounds with a vast presence in nature that have aroused a great interest for decades. In particular, hydroxyapatite (HAp, Ca10(OH)2(PO4)6) is the most abundant CaP mineral and is significant in the biological world, at least in part due to being a major compound in bones and teeth. HAp exhibits excellent properties, such as safety, stability, hardness, biocompatibility, and osteoconductivity, among others. Even some of its drawbacks, such as its fragility, can be redirected thanks to another essential feature: its great versatility. This is based on the compound's tendency to undergo substitutions of its constituent ions and to incorporate or anchor new molecules on its surface and pores. Thus, its affinity for biomolecules makes it an optimal compound for multiple applications, mainly, but not only, in biological and biomedical fields. The present review provides a chemical and structural context to explain the affinity of HAp for biomolecules such as proteins and nucleic acids to generate hybrid materials. A size-dependent criterium of increasing complexity is applied, ranging from amino acids/nucleobases to the corresponding macromolecules. The incorporation of metal ions or metal complexes into these functionalized compounds is also discussed.

Comparison of Key Properties of Ag-TiO2 and Hydroxyapatite-Ag-TiO2 Coatings on NiTi SMA

To functionalize the NiTi alloy, multifunctional innovative nanocoatings of Ag-TiO2 and Ag-TiO2 doped with hydroxyapatite were engineered on its surface. The coatings were thoroughly characterized, focusing on surface topography and key functional properties, including adhesion, surface wettability, biocompatibility, antibacterial activity, and corrosion resistance. The electrochemical corrosion kinetics in a simulated body fluid and the mechanisms were analyzed. The coatings exhibited hydrophilic properties and were biocompatible with fibroblast and osteoblast cells while also demonstrating antibacterial activity against E. coli and S. epidermidis. The coatings adhered strongly to the NiTi substrate, with superior adhesion observed in the hydroxyapatite-doped layers. Conversely, the Ag-TiO2 layers showed enhanced corrosion resistance.

Biomedical Composites of Polycaprolactone/Hydroxyapatite for Bioplotting: Comprehensive Interpretation of the Reinforcement Course

Robust materials in medical applications are sought after and researched, especially for 3D printing in bone tissue engineering. Poly[ε-caprolactone] (PCL) is a commonly used polymer for scaffolding and other medical uses. Its strength is a drawback compared to other polymers. Herein, PCL was mixed with hydroxyapatite (HAp). Composites were developed at various concentrations (0.0-8.0 wt. %, 2.0 step), aiming to enhance the strength of PCL with a biocompatible additive in bioplotting. Initially, pellets were derived from the shredding of filaments extruded after mixing PCL and HAp at predetermined quantities for each composite. Specimens were then manufactured by bioplotting 3D printing. The samples were tested for their thermal and rheological properties and were also mechanically, morphologically, and chemically examined. The mechanical properties included tensile and flexural investigations, while morphological and chemical examinations were carried out employing scanning electron microscopy and energy dispersive spectroscopy, respectively. The structure of the manufactured specimens was analyzed using micro-computed tomography with regard to both their dimensional deviations and voids. PCL/HAp 6.0 wt. % was the composite that showed the most enhanced mechanical (14.6% strength improvement) and structural properties, proving the efficiency of HAp as a reinforcement filler in medical applications.

Patient derived cancer organoids model the response to HER2-CD3 bispecific antibody (BsAbHER2) generated from hydroxyapatite gene delivery system

HER2-positive cancer is a prevalent subtype of malignancy with poor prognosis, yet current targeted therapies, like Trastuzumab and pyrotinib, have resulted in remission in patients with HER2-positive cancer. This study provides a novel approach for immunotherapy based on a hydroxyapatite (HA) gene delivery system producing a bispecific antibody for HER2-positive cancer treatment. An HA nanocarrier has been synthesized by the classical hydrothermal method. Particularly, the HA-nanoneedle system was able to mediate stable gene expression of minicircle DNA (MC) encoding a humanized anti-CD3/anti-HER2 bispecific antibody (BsAbHER2) in vivo. The produced BsAbs exhibited a potent killing effect not only in HER2-positive cancer cells but also in patient-derived organoids in vitro. This HA-nanoneedle gene delivery system features simple large-scale preparation and clinical applicability. Hence, the HA-nanoneedle gene delivery system combined with minicircle DNA vector encoding BsAbHER2 reported here provides a potential immunotherapy strategy for HER2-positive tumors.

Calcium Hydroxyapatite in Its Different Forms in Skin Tissue Repair: A Literature Review

The skin is crucial for homeostasis and body defense, requiring quick healing to maintain internal balance. Initially used for bone repair, calcium hydroxyapatite (HAp) is now being studied for soft tissue engineering. This literature review investigated HAp’s role in tissue repair through searches on PubMed, Scopus (Elsevier), Science Direct, Springer Link, and Google Scholar databases without time restrictions, using keywords “hydroxyapatite AND skin AND wound” and “hydroxyapatite AND skin repair”. Inclusion criteria encompassed in vivo studies in humans and animals, English publications, full access, and sufficient data on HAp’s role in tissue repair. Exclusions included duplicates, unrelated articles, editor letters, reviews, comments, conference abstracts, dissertations, and theses. Out of the 472 articles initially identified, 139 met the inclusion criteria, with 21 focusing on HAp for tissue repair. Findings indicate that HAp and nano-HAp in skin regeneration are promising, especially when combined with other biomaterials, offering antimicrobial and anti-inflammatory benefits and stimulating angiogenesis. This suggests their potential application in dermatology, surgery, and dentistry, extending HAp’s versatility from hard tissues to enhancing critical properties for soft tissue repair and accelerating healing.

Fishwaste Derived Hydroxyapatite Nanostructure Combined with Black Rice Wine for Potential Antioxidant and Antimicrobial Response

Hospital-acquired infection remains a serious threat globally, due to development of resistance to conventional antibiotics, which necessitates the urge for alternative therapy. Green nanotechnology has emerged as a holistic approach to address antibiotic resistance by combining environmental sustainability with improved therapeutic outcome. Nanostructure hydroxyapatite (HAP) has received significant attention in therapeutic and regenerative purposes due to its porous scaffold structure and biocompatible nature. In the present study, hydroxyapatite (HAP) nanoparticle was fabricated from the fish scale waste of red snapper fish. Black rice wine (BRW) was extracted from black rice commonly termed as Karupu kavuni/forbidden rice known for its nutritious effects. The present study focused on encapsulation of BRW within HAP nanoparticles (HAP@BRW) and evaluated its potential against nosocomial infections. Spectral and microscopic characterization of HAP@BRW revealed uniform encapsulation of BRW in HAP nanoparticles, aggregated irregular-shaped morphology of size 117.6 nm. Maximum release of BRW (72%) within 24 h indicates HAP as suitable drug delivery system suitable for biomedical applications. Antimicrobial studies revealed that HAP@BRW exhibited potent bactericidal effect against MRSA, MSSA, and Pseudomonas aeruginosa. Furthermore, HAP@BRW significantly inhibited the biofilm forming ability of MSSA and P. aeruginosa. Rich antioxidant property of HAP@BRW might be due to the presence of rich source of total polyphenolic, flavonoid, and anthocyanin content in BRW. In vitro and in vivo toxicity studies revealed biocompatible nature of HAP@BRW. Antibiofilm, antimicrobial, antioxidant, and biocompatible nature of HAP@BRW makes it a promising candidate for coating medical implants to avoid implant-associated infections and nosocomial infections.

Advances in Nanomedicine for Precision Insulin Delivery

Diabetes mellitus, which comprises a group of metabolic disorders affecting carbohydrate metabolism, is characterized by improper glucose utilization and excessive production, leading to hyperglycemia. The global prevalence of diabetes is rising, with projections indicating it will affect 783.2 million people by 2045. Insulin treatment is crucial, especially for type 1 diabetes, due to the lack of β-cell function. Intensive insulin therapy, involving multiple daily injections or continuous subcutaneous insulin infusion, has proven effective in reducing microvascular complications but poses a higher risk of severe hypoglycemia. Recent advancements in insulin formulations and delivery methods, such as ultra-rapid-acting analogs and inhaled insulin, offer potential benefits in terms of reducing hypoglycemia and improving glycemic control. However, the traditional subcutaneous injection method has drawbacks, including patient compliance issues and associated complications. Nanomedicine presents innovative solutions to these challenges, offering promising avenues for overcoming current drug limitations, enhancing cellular uptake, and improving pharmacokinetics and pharmacodynamics. Various nanocarriers, including liposomes, chitosan, and PLGA, provide protection against enzymatic degradation, improving drug stability and controlled release. These nanocarriers offer unique advantages, ranging from enhanced bioavailability and sustained release to specific targeting capabilities. While oral insulin delivery is being explored for better patient adherence and cost-effectiveness, other nanomedicine-based methods also show promise in improving delivery efficiency and patient outcomes. Safety concerns, including potential toxicity and immunogenicity issues, must be addressed, with the FDA providing guidance for the safe development of nanotechnology-based products. Future directions in nanomedicine will focus on creating next-generation nanocarriers with precise targeting, real-time monitoring, and stimuli-responsive features to optimize diabetes treatment outcomes and patient safety. This review delves into the current state of nanomedicine for insulin delivery, examining various types of nanocarriers and their mechanisms of action, and discussing the challenges and future directions in developing safe and effective nanomedicine-based therapies for diabetes management.

Green synthesis of nanohydroxyapatite with Elaeagnus angustifolia L. extract as a metronidazole nanocarrier for in vitro pulpitis model treatment

The aim of this study is to introduce a dental capping agent for the treatment of pulp inflammation (pulpitis). Nanohydroxyapatite with Elaeagnus angustifolia L. extract (nHAEA) loaded with metronidazole (nHAEA@MTZ) was synthesized and evaluated using a lipopolysaccharide (LPS) in vitro model of pulpitis. nHAEA was synthesized through sol-gel method and analyzed using Scanning Electron Microscopy, Transmission Electron Microscopy, and Brunauer Emmett Teller. Inflammation in human dental pulp stem cells (HDPSCs) induced by LPS. A scratch test assessed cell migration, RT PCR measured cytokines levels, and Alizarin red staining quantified odontogenesis. The nHAEA nanorods were 17-23 nm wide and 93-146 nm length, with an average pore diameter of 27/312 nm, and a surface area of 210.89 m2/g. MTZ loading content with controlled release, suggesting suitability for therapeutic applications. nHAEA@MTZ did not affect the odontogenic abilities of HDPSCs more than nHAEA. However, it was observed that nHAEA@MTZ demonstrated a more pronounced anti-inflammatory effect. HDPSCs treated with nanoparticles exhibited improved migration compared to other groups. These findings demonstrated that nHAEA@MTZ could be an effective material for pulp capping and may be more effective than nHAEA in reducing inflammation and activating HDPSCs to enhance pulp repair after pulp damage.

Shape Matters: Impact of Mesoporous Silica Nanoparticle Morphology on Anti-Tumor Efficacy

A nanoparticle's shape is a critical determinant of its biological interactions and therapeutic effectiveness. This study investigates the influence of shape on the performance of mesoporous silica nanoparticles (MSNs) in anticancer therapy. MSNs with spherical, rod-like, and hexagonal-plate-like shapes were synthesized, with particle sizes of around 240 nm, and their other surface properties were characterized. The drug loading capacities of the three shapes were controlled to be 47.46%, 49.41%, and 46.65%, respectively. The effects of shape on the release behaviors, cellular uptake mechanisms, and pharmacological behaviors of MSNs were systematically investigated. Through a series of in vitro studies using 4T1 cells and in vivo evaluations in 4T1 tumor-bearing mice, the release kinetics, cellular behaviors, pharmacological effects, circulation profiles, and therapeutic efficacy of MSNs were comprehensively assessed. Notably, hexagonal-plate-shaped MSNs loaded with PTX exhibited a prolonged circulation time (t1/2 = 13.59 ± 0.96 h), which was approximately 1.3 times that of spherical MSNs (t1/2 = 10.16 ± 0.38 h) and 1.5 times that of rod-shaped MSNs (t1/2 = 8.76 ± 1.37 h). This research underscores the significance of nanoparticles' shapes in dictating their biological interactions and therapeutic outcomes, providing valuable insights for the rational design of targeted drug delivery systems in cancer therapy.

Correlation between positron annihilation lifetime and photoluminescence measurements for calcined Hydroxyapatite

Hydroxyapatite (HAp) Ca10(PO4)6(OH)2 is a compound that has stable chemical properties, composition, and an affinity for human bone. As a result, it can be used in odontology, cancer treatment, and orthopedic grafts to repair damaged bone. To produce calcined HAp at 600 °C with different pH values, a wet chemical precipitation method was employed. All synthesized HAp samples were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), photoluminescence (PL), Zeta potential, and positron annihilation lifetime spectroscopy (PALS). The XRD results revealed that all calcined HAp samples were formed in a hexagonal structure with a preferred (002) orientation at different pH values. The crystal size of the samples was determined using the Scherrer equation, which ranged from 16 to 25 nm. The SEM and TEM results showed that the morphology of the samples varied from nanorods to nanospheres and rice-like structures depending on the pH value of the sample. The PL measurements indicated that the blue and green emission peaks of HAp were due to defects (bulk, surface, and interface) in the samples, which created additional energy levels within the band gap. According to Zeta potential measurements, the charge carrier changed from a positive to negative value, ranging from 3.94 mV to - 2.95 mV. PALS was used to understand the relationship between the defects and the photoluminescence (PL) properties of HAp. Our results suggest that HAp nanoparticles have excellent potential for developing non-toxic biomedical and optical devices for phototherapy.

Targeted Clindamycin Delivery Systems: Promising Options for Preventing and Treating Bacterial Infections Using Biomaterials

Targeted therapy represents a real opportunity to improve the health and lives of patients. Developments in this field are confirmed by the fact that the global market for drug carriers was worth nearly $40 million in 2022. For this reason, materials engineering and the development of new drug carrier compositions for targeted therapy has become a key area of research in pharmaceutical drug delivery in recent years. Ceramics, polymers, and metals, as well as composites, are of great interest, as when they are appropriately processed or combined with each other, it is possible to obtain biomaterials for hard tissues, soft tissues, and skin applications. After appropriate modification, these materials can release the drug directly at the site requiring a therapeutic effect. This brief literature review characterizes routes of drug delivery into the body and discusses biomaterials from different groups, options for their modification with clindamycin, an antibiotic used for infections caused by aerobic and anaerobic Gram-positive bacteria, and different methods for the final processing of carriers. Examples of coating materials for skin wound healing, acne therapy, and bone tissue fillers are given. Furthermore, the reasons why the use of antibiotic therapy is crucial for a smooth and successful recovery and the risks of bacterial infections are explained. It was demonstrated that there is no single proven delivery scheme, and that the drug can be successfully released from different carriers depending on the destination.

Recent advances of nanoparticles on bone tissue engineering and bone cells

With the development of biotechnology, biomaterials have been rapidly developed and shown great potential in bone regeneration therapy and bone tissue engineering. Nanoparticles have attracted the attention of researches and have applied in various fields especially in the biomedical field as the special physicochemical properties. Nanoparticles were found to regulate bone remodeling depending on their size, shape, composition, and charge. Therefore, in-depth research was necessary to provide the basic support to select the most suitable nanoparticles for bone relate diseases treatment. This article reviews the current development of nanoparticles in bone tissue engineering, focusing on drug delivery, gene delivery, and cell labeling. In addition, the research progress on the interaction of nanoparticles with bone cells, focusing on osteoblasts, osteoclasts, and bone marrow mesenchymal stem cells, and the underlying mechanism were also reviewed. Finally, the current challenges and future research directions are discussed. Thus, detailed study of nanoparticles may reveal new therapeutic strategies to improve the effectiveness of bone regeneration therapy or other bone diseases.

Effect of Surface Chemistry on Hemolysis, Thrombogenicity, and Toxicity of Carbon Nanotube Doped Thermally Sprayed Hydroxyapatite Implants

Assessing blood compatibility is crucial before in vivo procedures and is considered more reliable than many in vitro tests. This study examines the physiochemical properties and blood compatibility of bioactive powders ((0.5-2 wt % carbon nanotube (CNT)/alumina)-20 wt %)) produced through a heterocoagulation colloidal technique followed by ball milling with hydroxyapatite (HAp). The 1 wt % CNT composite demonstrated a surface charge ∼5 times higher than HAp at pH 7.4, with a value of -11 mV compared to -2 mV. This increase in electrostatic charge is desirable for achieving hemocompatibility, as evidenced by a range of blood compatibility assessments, including hemolysis, blood clotting, platelet adhesion, platelet activation, and coagulation assays (prothrombin time (PT) and activated partial thrombin time (aPTT)). The 1 wt % CNT composite exhibited hemolysis ranging from 2 to 7%, indicating its hemocompatibility. In the blood clot investigation, the absorbance values for 1-2 wt % CNT samples were 0.927 ± 0.038 and 1.184 ± 0.128, respectively, indicating their nonthrombogenicity. Additionally, the percentage of platelet adhered on the 1 wt % CNT sample (∼5.67%) showed a ∼2.5-fold decrement compared to the clinically used negative control, polypropylene (∼13.73%). The PT and aPTT experiments showed no difference in the coagulation time for CNT samples even at higher concentrations, unlike HAC2 (80 mg). In conclusion, the 1 wt % CNT sample was nontoxic to human blood, making it more hemocompatible, nonhemolytic, and nonthrombogenic than other samples. This reliable study reduces the need for additional in vitro and in vivo studies before clinical trials, saving time and cost.

Nanoparticle-Based Drug Delivery Systems for Enhancing Bone Regeneration

The treatment of bone defects has been a long-standing challenge in clinical practice. Among the various bone tissue engineering approaches, there has been substantial progress in the development of drug delivery systems based on functional drugs and appropriate carrier materials owing to technological advances in recent years. A large number of materials based on functional nanocarriers have been developed and applied to improve the complex osteogenic microenvironment, including for promoting osteogenic activity, inhibiting osteoclast activity, and exerting certain antibacterial effects. This Review discusses the physicochemical properties, drug loading mechanisms, advantages and disadvantages of nanoparticles (NPs) used for constructing drug delivery systems. In addition, we provide an overview of the osteogenic microenvironment regulation mechanism of drug delivery systems based on nanoparticle (NP) carriers and the construction strategies of drug delivery systems. Finally, the advantages and disadvantages of NP carriers are summarized along with their prospects and future research trends in bone tissue engineering. This Review thus provides advanced strategies for the design and application of drug delivery systems based on NPs in the treatment of bone defects.

Are hydroxyapatite-based biomaterials free of genotoxicity? A systematic review

Hydroxyapatite (HA) is a biomaterial widely used in clinical applications and pharmaceuticals. The literature on HA-based materials studies is focused on chemical characterization and biocompatibility. Generally, biocompatibility is analyzed through adhesion, proliferation, and differentiation assays. Fewer studies are looking for genotoxic events. Thus, although HA-based biomaterials are widely used as biomedical devices, there is a lack of literature regarding their genotoxicity. This systematic review was carried out following the PRISMA statement. Specific search strategies were developed and performed in four electronic databases (PubMed, Science Direct, Scopus, and Web of Science). The search used "Hydroxyapatite OR Calcium Hydroxyapatite OR durapatite AND genotoxicity OR genotoxic OR DNA damage" and "Hydroxyapatite OR Calcium Hydroxyapatite OR durapatite AND mutagenicity OR mutagenic OR DNA damage" as keywords and articles published from 2000 to 2022, after removing duplicate studies and apply include and exclusion criteria, 53 articles were identified and submitted to a qualitative descriptive analysis. Most of the assays were in vitro and most of the studies did not show genotoxicity. In fact, a protective effect was observed for hydroxyapatites. Only 20 out of 71 tests performed were positive for genotoxicity. However, no point mutation-related mutagenicity was observed. As the genotoxicity of HA-based biomaterials observed was correlated with its nanostructured forms as needles or rods, it is important to follow their effect in chronic exposure to guarantee safe usage in humans.

Zinc-doped hydroxyapatite as a pH responsive drug delivery system for anticancer drug 6-mercaptopurine

6-Mercaptopurine (6MP) is commonly used in the treatment of acute lymphoblastic leukemia as an important agent in maintenance therapy. Despite its therapeutic benefits, 6MP has some limitations during therapy. Taking into account the disadvantages during 6MP therapy, there is a great need to create an appropriate delivery system for this drug. 6MP contains in its structure nitrogen and sulfur atoms capable of forming coordination compounds with metal ions, for example zinc. Therefore, in this work, we prepared biocompatible hydroxyapatite (HAp) doped with zinc ions, and used it as a carrier for 6MP. Doped HAp has not been used as a carrier for this drug before. The work proved that the prepared carrier-drug system has a particle size of about 130 nm, which indicates its potential for intravenous delivery. In addition, in an acidic environment (imitating cancer cells), the carrier agglomerates allow targeted release of the drug. The drug is evenly distributed, which indicates that the doses released from it will always be comparable. The release of the drug in a neutral environment is long-lasting in controlled doses, whereas in an acidic environment it is immediate. The obtained results indicate the high potential of the material in both slow-release and cancer-targeted release of 6MP.

Magnetic Hydroxyapatite Nanoparticles in Regenerative Medicine and Nanomedicine

This review focuses on the latest advancements in magnetic hydroxyapatite (mHA) nanoparticles and their potential applications in nanomedicine and regenerative medicine. mHA nanoparticles have gained significant interest over the last few years for their great potential, offering advanced multi-therapeutic strategies because of their biocompatibility, bioactivity, and unique physicochemical features, enabling on-demand activation and control. The most relevant synthetic methods to obtain magnetic apatite-based materials, either in the form of iron-doped HA nanoparticles showing intrinsic magnetic properties or composite/hybrid compounds between HA and superparamagnetic metal oxide nanoparticles, are described as highlighting structure-property correlations. Following this, this review discusses the application of various magnetic hydroxyapatite nanomaterials in bone regeneration and nanomedicine. Finally, novel perspectives are investigated with respect to the ability of mHA nanoparticles to improve nanocarriers with homogeneous structures to promote multifunctional biological applications, such as cell stimulation and instruction, antimicrobial activity, and drug release with on-demand triggering.

Novel Synthesis Approach for Natural Tea Polyphenol-Integrated Hydroxyapatite

Hydroxyapatite (HAP) has garnered considerable interest in biomedical engineering for its diverse applications. Yet, the synthesis of HAP integrated with functional natural organic components remains an area ripe for exploration. This study innovatively utilizes the versatile properties of tea polyphenol (TP) to synthesize HAP nanomaterials with superior crystallinity and distinct morphologies, notably rod-like structures, via a chemical deposition process in a nitrogen atmosphere. This method ensures an enhanced integration of TP, as confirmed by thermogravimetric (TGA) analysis and a variety of microscopy techniques, which also reveal the dependence of TP content and crystallinity on the synthesis method employed. The research significantly impacts the field by demonstrating how synthesis conditions can alter material properties. It leads the way in employing TP-modified nano-HAP particles for biomedical applications. The findings of this study are crucial as they open avenues for the future development of tailored HAP nanomaterials, aiming at specific medical applications and advancements in nanotechnology.

Tumor therapy by targeting extracellular hydroxyapatite using novel drugs: A paradigm shift

BACKGROUND

It has been shown that tumor microenvironment (TME) hydroxyapatite (HAP) is typically associated with many malignancies and plays a role in tumor progression and growth. Additionally, acidosis in the TME has been reported to play a key role in selecting for a more aggressive tumor phenotype, drug resistance and desensitization to immunotherapy for many types of cancers. TME-HAP is an attractive target for tumor detection and treatment development since HAP is generally absent from normal soft tissue. We provide strong evidence that dissolution of hydroxyapatite (HAP) within the tumor microenvironment (TME-HAP) using a novel therapeutic can be used to kill cancer cells both in vitro and in vivo with minimal adverse effects.

METHODS

We developed an injectable cation exchange nano particulate sulfonated polystyrene solution (NSPS) that we engineered to dissolve TME-HAP, inducing localized acute alkalosis and inhibition of tumor growth and glucose metabolism. This was evaluated in cell culture using 4T1, MDA-MB-231 triple negative breast cancer cells, MCF10 normal breast cells, and H292 lung cancer cells, and in vivo using orthotopic mouse models of cancer that contained detectable microenvironment HAP including breast (MMTV-Neu, 4T1, and MDA-MB-231), prostate (PC3) and colon (HCA7) cancer using 18 F-NaF for HAP and 18 F-FDG for glucose metabolism with PET imaging. On the other hand, H292 lung tumor cells that lacked detectable microenvironment HAP and MCF10a normal breast cells that do not produce HAP served as negative controls. Tumor microenvironment pH levels following injection of NSPS were evaluated via Chemical Exchange Saturation (CEST) MRI and via ex vivo methods.

RESULTS

Within 24 h of adding the small concentration of 1X of NSPS (~7 μM), we observed significant tumor cell death (~ 10%, p < 0.05) in 4T1 and MDA-MB-231 cell cultures that contain HAP but ⟨2% in H292 and MCF10a cells that lack detectable HAP and in controls. Using CEST MRI, we found extracellular pH (pHe) in the 4T1 breast tumors, located in the mammary fat pad, to increase by nearly 10% from baseline before gradually receding back to baseline during the first hour post NSPS administration. in the tumors that contained TME-HAP in mouse models, MMTV-Neu, 4T1, and MDA-MB-231, PC3, and HCA7, there was a significant reduction (p<0.05) in 18 F-Na Fuptake post NSPS treatment as expected; 18 F-  uptake in the tumor = 3.8 ± 0.5 %ID/g (percent of the injected dose per gram) at baseline compared to 1.8 ±0.5 %ID/g following one-time treatment with 100 mg/kg NSPS. Of similar importance, is that 18 F-FDG uptake in the tumors was reduced by more than 75% compared to baseline within 24 h of treatment with one-time NSPS which persisted for at least one week. Additionally, tumor growth was significantly slower (p < 0.05) in the mice treated with one-time NSPS. Toxicity showed no evidence of any adverse effects, a finding attributed to the absence of HAP in normal soft tissue and to our therapeutic NSPS having limited penetration to access HAP within skeletal bone.

CONCLUSION

Dissolution of TME-HAP using our novel NSPS has the potential to provide a new treatment paradigm to enhance the management of cancer patients with poor prognosis.

Hydroxyapatite Nanorods Based Drug Delivery Systems for Bumetanide and Meloxicam, Poorly Water Soluble Active Principles

Poorly water-soluble drugs represent a challenge for the pharmaceutical industry because it is necessary to find properly tuned and efficient systems for their release. In this framework, organic-inorganic hybrid systems could represent a promising strategy. A largely diffused inorganic host is hydroxyapatite (HAP, Ca10(PO4)6(OH)2), which is easily synthesized with different external forms and can adsorb different kinds of molecules, thereby allowing rapid drug release. Hybrid nanocomposites of HAP nanorods, obtained through hydrothermal synthesis, were prepared with two model pharmaceutical molecules characterized by low and pH-dependent solubility: meloxicam, a non-steroidal anti-inflammatory drug, and bumetanide, a diuretic drug. Both hybrids were physically and chemically characterized through the combined use of X-ray powder diffraction, scanning electron microscopy with energy-dispersive spectroscopy, differential scanning calorimetry, and infrared spectroscopy measurements. Then, their dissolution profiles and hydrophilicity (contact angles) in different media as well as their solubility were determined and compared to the pure drugs. This hybrid system seems particularly suitable as a drug carrier for bumetanide, as it shows higher drug loading and good dissolution profiles, while is less suitable for meloxicam, an acid molecule.

High doses of hydroxyapatite nanoparticle (nHAP) impairs microcirculation in vivo

Nanoparticles has surrounded the population by their use in electronics, medicine and cosmetics. The exposure to nanoparticles coming from different sources is uncountable as the amount of nanoparticles in which a person is exposed daily. In this direction and considering that microcirculation is the main and most affected system by nanoparticles in the first moment, responsible to transport and deal with nanoparticles internally, we evaluated a massive exposure (1 g/Kg) of a well-known nanoparticle (hydroxyapatite) and the impact on the microvessels. The results showed a massive destruction of venules, arterioles, and capillaries when nHAPs were administered topically. However, systemic administration of high doses of nHAP did not affect microcirculation but altered biochemical parameters of blood samples from treated animals. The data demonstrated that even well documented nanoparticles at high doses might affect the whole-body homeostasis. Finally, the results raise the necessity for further investigation of the effect of nanoparticles in microcirculation and the impact in the whole-body homeostasis.

Marine polysaccharides, proteins, lipids, and silica for drug delivery systems: A review

Marine environments represent an incredible source of biopolymers with potential biomedical applications. Recently, drug delivery studies have received great attention for the increasing need to improve site specificity, therapeutic value, and bioavailability, reducing off-target effects. Marine polymers, such as alginate, carrageenan, collagen, chitosan, and silica, have reported unique biochemical features, allowing an efficient binding with drugs, and a controlled release to the target tissue, also obtainable through "green processes". In the present review, we i) analysed the last ten years of scientific peer-reviewed literature; ii) divided the articles based on the achieved experimental phases, tagged as chemistry, drug release, and drug delivery, and iii) compared the best performances among marine polymers extracted from micro- and macro-organisms. Many reviews describe drug carriers from marine organisms, focusing on a single biopolymer or a chemical class. Our study is a groundbreaking literature collection, representing the first thorough investigation of all marine biopolymers described. Most articles report experimental results on the chemical characterisation of marine biopolymers and their in vitro behaviour as drug carriers, although development processes and commercial applications are still in the early stages. Hence, the next efforts should be focused on the sustainable production of marine polymers and final product development.

Preparation of core-shell composite materials capable of slowly releasing phosphate and their remediation performance of uranium-contaminated groundwater

Acid in-situ leach uranium mining significantly alters the geochemistry of the ore zone, and leaves uranium, residual acid, as well as other potential contaminants in groundwater, which bring harm to human health and ecological environment. Many investigators have been trying to propose remediation strategies for the uranium-contaminated groundwater. Phosphate is an effective immobilization reagent of uranium in the groundwater. However, direct injection of phosphate tends to quickly form precipitates, resulting in fast blockage of the seepage passages in the ore zone around the injection holes and hindering its diffusion. In this paper, HAP@SiO2-600, HAP@SiO2-600@25SA, and HAP@SiO2-600@75SA with core-shell structures were prepared. Their slow-release of phosphate, the effects of pH, contact time, initial uranium concentration, and coexisting ions on their removal rate and efficiency of uranium, and their function of remediating uranium-contaminated groundwater were investigated. It was found that the increase of SA content in the outer layer of HAP@SiO2-600@25SA and HAP@SiO2-600@75SA resulted in the slow release rate of phosphate, decreasing the removal rate of uranium. The adsorption capacities of HAP@SiO2-600, HAP@SiO2-600@25SA, and HAP@SiO2-600@75SA from the aqueous solution at pH = 3.0 and 303 K were up to 582.6, 558.5, and 507.3 mg g-1, respectively. In addition, the materials showed excellent uranium removal performance in experiments where multiple ions coexisted. For actual acidic uranium-contaminated groundwater, HAP@SiO2-600, HAP@SiO2-600@25SA, and HAP@SiO2-600@75SA effectively increased the pH from 2.75 to 4.40, 3.87, and 3.72, respectively, and decreased the uranium concentration from 5.12 to 0.0062, 0.0065, and 0.0058 mg L-1, respectively. The FT-IR, XRD, TEM and XPS characterizations were performed to further clarify the uranium removal mechanism, and it was found that the elimination of U(VI) was ascribed to dissolution-precipitation, adsorption and ion exchange. The results show that the core-shell composite material capable of slowly releasing phosphate is effective in remediating uranium-contaminated groundwater.

Additive manufacturing of poly (lactic acid)/hydroxyapatite/carbon nanotubes biocomposites for fibroblast cell proliferation

Bone tissue is one of the most important in the human body. In this study, scaffolds of poly (lactic acid) PLA reinforced with hydroxyapatite (HA) and carbon nanotubes (CNT) were manufactured, evaluating their mechanical and biological properties. HA was synthesized by wet method and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The scaffolds were produced using additive manufacturing and characterized by optical microscopy, SEM, thermogravimetric analysis (TGA), Raman spectroscopy and biological tests. The SEM results showed that the PLA surface was affected by the incorporation of CNT. TG showed that the incorporation of HA into the polymer matrix compromised the thermal stability of PLA. On the other hand, the incorporation of CNT to the polymer and the impregnation with HA on the surface by thermal effect increased the stability of PLA/CNT scaffolds. Raman spectra indicated that HA impregnation on the surface did not modify the polymer or the ceramic. In the compression tests, PLA and PLA/CNT scaffolds displayed the best compressive strength. In the biological tests, more than 85% of the cells remained viable after 48 h of incubation with all tested scaffolds and groups with CNT in the composition disclosing the best results.

In-situ micro-CT scanning and compressive strength assessment of diammonium hydrogen phosphate (DAP) treated chalk

The occurrence of wellbore mechanical failure is a consequence of the interaction among factors such as in situ stress, rock strength, and engineering procedures. The process of hydrocarbons production, causing reduction of pore pressure, alters the effective stresses in the vicinity of a borehole, leading to borehole instability issues. Estimating the rocks' elastic modulus and compressive strength is essential to comprehend the rock matrix's mechanical response during drilling and production operations. This study aimed to assess the practicality of Diammonium Hydrogen Phosphate (DAP) application as a chemical for strengthening chalk in hydrocarbon reservoirs, to make it resistant to high stresses and failure during drilling and production. The mechanical and physical properties of Austin chalk rock samples treated with DAP under mimicked reservoir conditions were studied. The results showed that DAP is a highly effective carbonate rock consolidating agent that improves the mechanical strength of the chalk. Compressive test measurements conducted on rocks treated at two different temperatures (ambient and 50 °C) showed that DAP effectively strengthened the rock matrix, resulting in an increase in its compressive strength (22-24%) and elastic modulus (up to 115%) compared to the untreated sample. The favorable outcomes of this research suggest that the DAP solution holds promise as a consolidation agent in hydrocarbon reservoirs. This contributes to the advancement of knowledge regarding effective strategies for mitigating mechanical failures of the wellbore during drilling and production.

The Influence of Polyvinyl Alcohol Porogen Addition on the Nanostructural Characteristics of Hydroxyapatite

Hydroxyapatite (HA) is a porous material widely developed in various research fields because of its high biodegradability, biocompatibility, and low toxicity. In this research, HA was synthesized using a hydrothermal method with chicken eggshells as a calcium source and various concentrations of polyvinyl alcohol as a porogen (2.5%, 5.0%, and 7.5% by wt). The structure and morphology of HA were determined by X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. HA was obtained with varying concentrations of polyvinyl alcohol (PVA) porogen according to Inorganic Crystal Structure Database (ICSD) standard. Based on analysis using a refinement method, changes in unit cell parameters (cell volume and lattice strain) of HA synthesized using PVA porogen compared to the standard, the chi square (χ2) and index of R values were relatively low, validating the acceptable of the data. In addition, HA [Ca10(PO4)6(OH)2] with hexagonal structure and the P63/m space group was successfully obtained. Morphological analysis of HA by SEM found that HA has a spherical shape, and the porosity of HA increases with increasing concentrations of polyvinyl alcohol. The highest porosity was obtained with an addition of 5.0 wt% of PVA porogen (HAP3), reaching 69.53%.

Drug Delivery and Therapy Strategies for Osteoporosis Intervention

With the advent of the aging society, osteoporosis (OP) risk increases yearly. Currently, the clinical usage of anti-OP drugs is challenged by recurrent side effects and poor patient compliance, regardless of oral, intravenous, or subcutaneous administration. Properly using a drug delivery system or formulation strategy can achieve targeted drug delivery to the bone, diminish side effects, improve bioavailability, and prolong the in vivo residence time, thus effectively curing osteoporosis. This review expounds on the pathogenesis of OP and the clinical medicaments used for OP intervention, proposes the design approach for anti-OP drug delivery, emphatically discusses emerging novel anti-OP drug delivery systems, and enumerates anti-OP preparations under clinical investigation. Our findings may contribute to engineering anti-OP drug delivery and OP-targeting therapy.

Hydroxyapatite nanoparticles induced calcium overload-initiated cancer cell-specific apoptosis through inhibition of PMCA and activation of calpain

Hydroxyapatite nanoparticles (HAPNs) have been reported to specifically induce apoptosis and sustained elevation of intracellular Ca2+ concentration ([Ca2+]i) in cancer cells. However, it remains unclear whether calcium overload, the abnormal intracellular accumulation of Ca2+, is the intrinsic cause of cell apoptosis, how HAPNs specifically evoke calcium overload in cancer cells, and which potential pathways were involved in apoptosis initiation in response to calcium overload. In this study, using various cancer and normal cells, we observed a positive correlation between the degree of increased [Ca2+]i and the specific toxicity of HAPNs. Moreover, chelating intracellular Ca2+ with BAPTA-AM inhibited HAPN-induced calcium overload and apoptosis, thus demonstrating that calcium overload was the main cause of HAPN-induced cytotoxicity in cancer cells. Notably, the dissolution of particles outside the cells did not affect cell viability or [Ca2+]i. In contrast, internalized HAPNs dissolved more readily in cancer cells than in normal cells and inhibited the activity of plasma membrane calcium-ATPase solely in cancer cells to prevent extrusion of excessive Ca2+, hence leading to calcium overload in tumor cells. Upon exposure to HAPNs, the Ca2+-sensitive cysteine protease calpain was activated and then cleaved the BH3-only protein Bid. Consequently, cytochrome c was released, and caspase-9 and -3 were activated, leading to mitochondrial apoptosis. However, these effects were alleviated by the calpain inhibitor calpeptin, confirming the involvement of calpain in HANP-induced apoptosis. Therefore, our results demonstrated that calcium overload induced by HAPNs caused cancer cell-specific apoptosis by inhibiting PMCA and activating calpain in tumor cells and thus may contribute to a more comprehensive understanding of biological effects of this nanomaterial and facilitate the development of calcium overload cancer therapy.

A Comparative Study of HA/DBM Compounds Derived from Bovine and Porcine for Bone Regeneration

This comparative study investigated the tissue regeneration and inflammatory response induced by xenografts comprised of hydroxyapatite (HA) and demineralized bone matrix (DBM) extracted from porcine (P) and bovine (B) sources. First, extraction of HA and DBM was independently conducted, followed by chemical and morphological characterization. Second, mixtures of HA/DBM were prepared in 50/50 and 60/40 concentrations, and the chemical, morphological, and mechanical properties were evaluated. A rat calvarial defect model was used to evaluate the tissue regeneration and inflammatory responses at 3 and 6 months. The commercial allograft DBM Puros® was used as a clinical reference. Different variables related to tissue regeneration were evaluated, including tissue thickness regeneration (%), amount of regenerated bone area (%), and amount of regenerated collagen area (%). The inflammatory response was evaluated by quantifying the blood vessel area. Overall, tissue regeneration from porcine grafts was superior to bovine. After 3 months of implantation, the tissue thickness regeneration in the 50/50P compound and the commercial DBM was significantly higher (~99%) than in the bovine materials (~23%). The 50/50P and DBM produced higher tissue regeneration than the naturally healed controls. Similar trends were observed for the regenerated bone and collagen areas. The blood vessel area was correlated with tissue regeneration in the first 3 months of evaluation. After 6 months of implantation, HA/DBM compounds showed less regenerated collagen than the DBM-only xenografts. In addition, all animal-derived xenografts improved tissue regeneration compared with the naturally healed defects. No clinical complications associated with any implanted compound were noted.

Hydrothermal Transformation of Eggshell Calcium Carbonate into Apatite Micro-Nanoparticles: Cytocompatibility and Osteoinductive Properties

The eggshell is a biomineral consisting of CaCO3 in the form of calcite phase and a pervading organic matrix (1-3.5 wt.%). Transforming eggshell calcite particles into calcium phosphate (apatite) micro-nanoparticles opens the door to repurposing the eggshell waste as materials with potential biomedical applications, fulfilling the principles of the circular economy. Previous methods to obtain these particles consisted mainly of two steps, the first one involving the calcination of the eggshell. In this research, direct transformation by a one-pot hydrothermal method ranging from 100-200 °C was studied, using suspensions with a stoichiometric P/CaCO3 ratio, K2HPO4 as P reagent, and eggshells particles (Ø < 50 μm) both untreated and treated with NaClO to remove surface organic matter. In the untreated group, the complete conversion was achieved at 160 °C, and most particles displayed a hexagonal plate morphology, eventually with a central hole. In the treated group, this replacement occurred at 180 °C, yielding granular (spherulitic) apatite nanoparticles. The eggshell particles and apatite micro-nanoparticles were cytocompatible when incubated with MG-63 human osteosarcoma cells and m17.ASC murine mesenchymal stem cells and promoted the osteogenic differentiation of m17.ASC cells. The study results are useful for designing and fabricating biocompatible microstructured materials with osteoinductive properties for applications in bone tissue engineering and dentistry.

Marine Biomaterials: Hyaluronan

The marine-derived hyaluronic acid and other natural biopolymers offer exciting possibilities in the field of biomaterials, providing sustainable and biocompatible alternatives to synthetic materials. Their unique properties and abundance in marine sources make them valuable resources for various biomedical and industrial applications. Due to high biocompatible features and participation in biological processes related to tissue healing, hyaluronic acid has become widely used in tissue engineering applications, especially in the wound healing process. The present review enlightens marine hyaluronan biomaterial providing its sources, extraction process, structures, chemical modifications, biological properties, and biocidal applications, especially for wound healing/dressing purposes. Meanwhile, we point out the future development of wound healing/dressing based on hyaluronan and its composites and potential challenges.

Emerging nano-scale delivery systems for the treatment of osteoporosis

Osteoporosis is a pathological condition characterized by an accelerated bone resorption rate, resulting in decreased bone density and increased susceptibility to fractures, particularly among the elderly population. While conventional treatments for osteoporosis have shown efficacy, they are associated with certain limitations, including limited drug bioavailability, non-specific administration, and the occurrence of adverse effects. In recent years, nanoparticle-based drug delivery systems have emerged as a promising approach for managing osteoporosis. Nanoparticles possess unique physicochemical properties, such as a small size, large surface area-to-volume ratio, and tunable surface characteristics, which enable them to overcome the limitations of conventional therapies. These nanoparticles offer several advantages, including enhanced drug stability, controlled release kinetics, targeted bone tissue delivery, and improved drug bioavailability. This comprehensive review aims to provide insights into the recent advancements in nanoparticle-based therapy for osteoporosis. It elucidates the various types of nanoparticles employed in this context, including silica, polymeric, solid lipid, and metallic nanoparticles, along with their specific processing techniques and inherent properties that render them suitable as potential drug carriers for osteoporosis treatment. Furthermore, this review discusses the challenges and future suggestions associated with the development and translation of nanoparticle drug delivery systems for clinical use. These challenges encompass issues such as scalability, safety assessment, and regulatory considerations. However, despite these challenges, the utilization of nanoparticle-based drug delivery systems holds immense promise in revolutionizing the field of osteoporosis management by enabling more effective and targeted therapies, ultimately leading to improved patient outcomes.

Hybrid Nanocomposites of Tenoxicam: Layered Double Hydroxides (LDHs) vs. Hydroxyapatite (HAP) Inorganic Carriers

The search for effective systems to facilitate the release of poorly bioavailable drugs is a forefront topic for the pharmaceutical market. Materials constituted by inorganic matrices and drugs represent one of the latest research strategies in the development of new drug alternatives. Our aim was to obtain hybrid nanocomposites of Tenoxicam, an insoluble nonsteroidal anti-inflammatory drug, with both layered double hydroxides (LDHs) and hydroxyapatite (HAP). The physicochemical characterization on the base of X-ray powder diffraction, SEM/EDS, DSC and FT-IR measurements was useful to verify the possible hybrids formation. In both cases, the hybrids formed, but it seemed that the drug intercalation in LDH was low and, in fact, the hybrid was not effective in improving the pharmacokinetic properties of the drug alone. On the contrary, the HAP-Tenoxicam hybrid, compared to the drug alone and to a simple physical mixture, showed an excellent improvement in wettability and solubility and a very significant increase in the release rate in all the tested biorelevant fluids. It delivers the entire daily dose of 20 mg in about 10 min.

Hierarchical and urchin-like chitosan/hydroxyapatite microspheres as drug-laden cell carriers

Biopolymer/hydroxyapatite (HAp) composites are one type of the most promising materials for a variety of biomedical applications. In this study, hierarchical and urchin-like chitosan/HAp nanowire (HU-CS/HAp NW) microspheres were for the first time synthesized by in situ hydrothermal treatment of chitosan/HAp (CS/HAp) microspheres in the acetic acid solution. The results indicate that HU-CS/HAp NW microspheres were spherical in morphology with a diameter of 100-300 μm. Their surface was mainly constructed by numerous HAp NWs with the diameter of 80-120 nm and showed a hierarchical and urchin-like nanofibrous architecture. It was found that the acidic hydrothermal treatment caused an in situ conversion of HAp NPs to HAp NWs. In vitro biocompatible evaluation indicates that HU-CS/HAp NW microspheres showed an enhanced cell attachment and proliferation due to the presence of hierarchical and urchin-like architecture. Furthermore, HU-CS/HAp NW microspheres showed a good adsorption capacity for tetracycline hydrochloride (model drug, one of the most representative antibiotics) with a higher adsorption capacity than CS/HAp microspheres and well maintained their antibacterial efficacy to inhibit the growth of bacteria: Escherichia coli and Staphylococcus aureus. Thus, the present HU-CS/HAp NW microspheres would be applicable as novel drug-laden cell carriers.

A review on microfluidic-assisted nanoparticle synthesis, and their applications using multiscale simulation methods

Recent years have witnessed an increased interest in the development of nanoparticles (NPs) owing to their potential use in a wide variety of biomedical applications, including drug delivery, imaging agents, gene therapy, and vaccines, where recently, lipid nanoparticle mRNA-based vaccines were developed to prevent SARS-CoV-2 causing COVID-19. NPs typically fall into two broad categories: organic and inorganic. Organic NPs mainly include lipid-based and polymer-based nanoparticles, such as liposomes, solid lipid nanoparticles, polymersomes, dendrimers, and polymer micelles. Gold and silver NPs, iron oxide NPs, quantum dots, and carbon and silica-based nanomaterials make up the bulk of the inorganic NPs. These NPs are prepared using a variety of top-down and bottom-up approaches. Microfluidics provide an attractive synthesis alternative and is advantageous compared to the conventional bulk methods. The microfluidic mixing-based production methods offer better control in achieving the desired size, morphology, shape, size distribution, and surface properties of the synthesized NPs. The technology also exhibits excellent process repeatability, fast handling, less sample usage, and yields greater encapsulation efficiencies. In this article, we provide a comprehensive review of the microfluidic-based passive and active mixing techniques for NP synthesis, and their latest developments. Additionally, a summary of microfluidic devices used for NP production is presented. Nonetheless, despite significant advancements in the experimental procedures, complete details of a nanoparticle-based system cannot be deduced from the experiments alone, and thus, multiscale computer simulations are utilized to perform systematic investigations. The work also details the most common multiscale simulation methods and their advancements in unveiling critical mechanisms involved in nanoparticle synthesis and the interaction of nanoparticles with other entities, especially in biomedical and therapeutic systems. Finally, an analysis is provided on the challenges in microfluidics related to nanoparticle synthesis and applications, and the future perspectives, such as large-scale NP synthesis, and hybrid formulations and devices.