Synthesis of hydroxyapatite for biomedical applications

Hydroxyapatite microspheres encapsulated within hybrid hydrogel promote skin regeneration through the activation of Calcium Signaling and Motor Protein pathway

Hydroxyapatite (HAp), traditionally recognized for its efficacy in bone regeneration, has rarely been explored for skin regeneration applications. This investigation explored HAp microspheres with distinct physicochemical properties tailored away from conventional bone regeneration parameters, and the capacity promoting skin regeneration and mitigating the aging process were investigated when encapsulated in hyaluronate hydrogels. By benchmarking against well-established dermal fillers like PMMA and PLLA, it was revealed the specific attributes of HAp that were conducive to skin regeneration, providing initial insights into the underlying mechanism. HAp enhanced the fibroblast functionality by triggering minimal adaptive immune responses and enhancing the Calcium Signaling and Motor Protein Signaling pathways. This modulation supported the production of normal collagen fibers, essential for ECM maturation and skin structural integrity. The significant ECM regeneration and remodeling capabilities exhibited by the HAp-encapsulated hybrid hydrogels suggested promising application in facial rejuvenation procedures, potentially making a breakthrough in aesthetic and reconstructive surgery.

Advances of Hydroxyapatite Nanoparticles in Dental Implant Applications

Hydroxyapatite nanoparticles (HANPs) are becoming increasingly crucial in dental implant applications as they are highly compatible with biological systems, actively support biological processes, and closely resemble bone minerals. This review covers the latest progress in how HANPs are made, studied, and used in dentistry. It looks at critical methods for creating HANPs, such as sol-gel, microwave hydrothermal synthesis, and biomimetic approaches, and how they affect the particles' size, structure, and activity. The green synthesis method illustrated a new door to synthesize HAp for maintaining biocompatibilityand increasing antibacterial properties. The review also explores how HANPs improve the integration of implants with bone, support bone growth, and help treat sensitive teeth based on various laboratory and clinical studies. The usage of HAp in dentin and enamel shows higher potentiality through FTIR, XPS, XRD, EDS, etc., for mechanical stability and biological balance compared to natural teeth. Additionally, the use of HANPs in dental products like toothpaste and mouthwash is discussed, highlighting its potential to help rebuild tooth enamel and fight bacteria. There are some challenges for long-term usage against oral bacteria, but doping with inorganic materials, like Zn, has already solved this periodontal problem. Much more research is still essential to estimate the fabrication variation based on patient problems and characteristics. Still, it has favorable outcomes regarding its bioactive nature and antimicrobial properties. Due to their compatibility with biological tissues and ability to support bone growth, HANPs hold great promise for advancing dental materials and implant technology, potentially leading to better dental care and patient outcomes.

A review on innovations in hydroxyapatite: advancing sustainable and multifunctional dental implants

The increasing relevance of biomaterials in medical curements and the care of aging populations has led to significant advancements in the development and modification of these materials. Hydroxyapatite (HAp), a biocompatible ceramic that mimics the composition of bone mineral, stands out for its remarkable abilities. Its stability in body fluids and ability to integrate with bone without causing toxicity or inflammation made it a prime candidate for biomedical utilization, particularly in odontology and orthopedics. Dental implants, which necessitate a strong interface with the jawbone to effectively support prosthetic devices, are enhanced by coatings of calcium phosphate-based materials like HAp. This enhances osseointegration, ensuring a strong bond and longevity of the implant. HAp may be synthesized both synthetically and from natural sources like mammalian bones, marine shells, and plants, each offering unique trace elements that improve its bioactivity. The synthesis of HAp involves differential technique, including chemical precipitation, and hydrothermal techniques, each impacting the final abilities of the material. The use of natural sources is especially promising, providing a sustainable, cost-effective alternative that retains essential biocompatibility. Hence, this article aims to explore the synthesis, properties, and biomedical applications of hydroxyapatite (HAp), with a special emphasis on its role in improving the performance and durability of dental implants. It also addresses the challenges in manufacturing and biocompatibility, offering insights into future advancements in this field. By addressing current challenges in manufacturing and biocompatibility, HAp paves the way for more effective and long-lasting dental treatments.

Nanomaterials-Based Drug Delivery Systems for Therapeutic Applications in Osteoporosis

The etiology of osteoporosis is rooted in the disruption of the intricate equilibrium between bone formation and bone resorption processes. Nevertheless, the conventional anti-osteoporotic medications and hormonal therapeutic regimens currently employed in clinical practice are associated with a multitude of adverse effects, thereby constraining their overall therapeutic efficacy and potential. Recently, nanomaterials have emerged as a promising alternative due to their minimal side effects, efficient drug delivery, and ability to enhance bone formation, aiding in restoring bone balance. This review delves into the fundamental principles of bone remodeling and the bone microenvironment, as well as current clinical treatment approaches for osteoporosis. It subsequently explores the research status of nanomaterial-based drug delivery systems for osteoporosis treatment, encompassing inorganic nanomaterials, organic nanomaterials, cell-mimicking carriers and exosomes mimics and emerging therapies targeting the osteoporosis microenvironment. Finally, the review discusses the potential of nanomedicine in treating osteoporosis and outlines the future trajectory of this burgeoning field. The aim is to provide a comprehensive reference for the application of nanomaterial-based drug delivery strategies in osteoporosis therapy, thereby fostering further advancements and innovations in this critical area of medical research.

A deformable SIS/HA composite hydrogel coaxial scaffold promotes alveolar bone regeneration after tooth extraction

After tooth extraction, alveolar bone absorbs unevenly, leading to soft tissue collapse, which hinders full regeneration. Bone loss makes it harder to do dental implants and repairs. Inspired by the biological architecture of bone, a deformable SIS/HA (Small intestinal submucosa/Hydroxyapatite) composite hydrogel coaxial scaffold was designed to maintain bone volume in the socket. The SIS/HA scaffold containing GL13K as the outer layer, mimicking compact bone, while SIS hydrogel loaded with bone marrow mesenchymal stem cells-derived exosomes (BMSCs-Exos) was utilized as the inner core of the scaffolds, which are like soft tissue in the skeleton. This coaxial scaffold exhibited a modulus of elasticity of 0.82 MPa, enabling it to adaptively fill extraction sockets and maintain an osteogenic space. Concurrently, the inner layer of this composite scaffold, enriched with BMSCs-Exos, promoted the proliferation and migration of human umbilical vein endothelial cells (HUVECs) and BMSCs into the scaffold interior (≈3-fold to the control), up-regulated the expression of genes related to osteogenesis (BMP2, ALP, RUNX2, and OPN) and angiogenesis (HIF-1α and VEGF). This induced new blood vessels and bone growth within the scaffold, addressing the issue of low bone formation rates at the center of defects. GL13K was released by approximately 40.87 ± 4.37 % within the first three days, exerting a localized antibacterial effect and further promoting vascularization and new bone formation in peripheral regions. This design aims to achieve an all-around and efficient bone restoration effect in the extraction socket using coaxial scaffolds through a dual internal and external mechanism.

A methodological comparison of synthesizing heavy metal substituted bioapatite

This study evaluates two methods-maturation and direct precipitation-for synthesizing heavy metal substituted biomimetic hydroxyapatite (HA), focusing on their efficacy in mimicking human bone composition and crystallinity. Cobalt (Co) and chromium (Cr) substitutions were investigated due to their relevance to metal-on-metal implant degradation and the potential integration of these ions into bone mineral. The maturation method involves prolonged incubation, producing amorphous and bioresorbable apatites, while the direct precipitation (DP) method achieves rapid synthesis of highly crystalline apatites through controlled titration. Both approaches were characterized using X-ray diffraction (XRD), Raman spectroscopy, and Fourier Transform Infrared (FTIR) spectroscopy, confirming the apatitic nature of the samples and lattice strain induced by metal ion substitution. This study highlights the maturation method's adaptability for long-term biological interactions and the DP method's mechanical stability for load-bearing applications. Comparison of the structural and chemical properties of substituted HA from each method provides insights into optimizing synthesis techniques for diverse biomedical applications, such as bone tissue engineering and mitigating the effects of heavy metal ion release on bone health. These findings contribute to advancing hydroxyapatite-based biomaterials tailored for therapeutic and regenerative medicine needs.

Evaluating the Toxicity of Synthetic Hydroxyapatite Nanoparticles (HAPNPs) against Pulse Beetle, Callosobruchus maculatus (Insecta: Coleoptera)

The pulse beetle Callosobruchus maculatus is a serious insect pest of stored legumes. Therefore, the management of such pests has become a necessity as it causes great economic loss to its plant host. Unfortunately, pest management programs against C. maculatus encounter several obstacles, such as the generation of insecticide resistance and environmental hazards of traditional insecticides. The current study was designed to overcome these obstacles by using synthetic nanoparticles as alternative insecticides. In this study, a synthetic form of eggshell-based hydroxyapatite nanoparticles (HAPNPs) was used as a control agent against C. maculatus. This material was selected because of its environmental safety, which is ensured due to its wide spectrum of applications in our daily activities. HAPNPs originating from eggshells were characterized by XRD, FTIR, and TEM. The obtained results revealed a lack of impurities in the synthesized particles and that the average plate size is ∼62.8 nm, while the rod structure has a length and width of ∼91 nm and ∼22.7 nm, respectively. A comparative study on the toxicity of HAPNPs and Malathion insecticide against C. maculatus showed a significant impact of NPs originating from eggshells than the positive control insecticide. Based on this finding, further analyses were performed to understand its subsequent effects. Eggshell-based HAPNPs disrupted C. maculatus fecundity and adult emergence rate. In the meantime, it highly reduced the negative effects of C. maculatus on cowpea seeds. Scanning electron microscopy showed clear disruption of the insect integument wax layer and the aggregation of HAPNPs on the beetle's spiracles, leading to respiratory failure and hence the death of the insects. Interestingly, there was no impact of HAPNP application on total antioxidants and H2O2 levels in C. maculatus. These results introduce a novel management tool using a safer nanopesticide against the cowpea beetle.

Recent advances of silver nanoparticle-based polymer nanocomposites for biomedical applications

Silver nanoparticle-polymer nanocomposites (AgNP-PNCs) represent a transformative advancement in biomedical material science, integrating the potent antimicrobial properties of AgNPs with the structural versatility of polymer matrices. This synergy enables enhanced infection control, mechanical stability, and controlled drug delivery, making these nanocomposites highly suitable for applications such as wound healing, medical coatings, tissue engineering, and biosensors. Recent progress in synthesis and functionalization has led to greater control over particle morphology, dispersion, and stability, optimizing AgNP-PNCs for clinical and translational applications. However, challenges related to cytotoxicity, long-term stability, immune response, and scalability persist, necessitating systematic improvements in surface functionalization, hybridization strategies, and biocompatibility assessments. This review critically evaluates the latest advancements in AgNP-PNC development, focusing on their functionalization techniques, regulatory considerations, and emerging strategies to overcome biomedical challenges. Additionally, it discusses preclinical and translational aspects, including commercialization barriers and regulatory frameworks such as FDA and EMA guidelines, ensuring a comprehensive outlook on their clinical feasibility. By bridging the gap between innovation and practical application, this review investigates the transformative potential of AgNP-PNCs in advancing next-generation biomedical materials.

Properties and antibacterial effectiveness of metal-ion doped borate-based bioactive glasses

Bioactive glasses (BGs) are physiologically reactive surface biomaterials widely used in biomedical applications and various treatments. Borate bioactive glasses (BBGs) are third-generation BGs, and they exhibit superior biodegradable, bioactive, osteoconductive, antibacterial, and biocompatible properties compared to other types of BGs. Certain concentrations of dopant ions can be incorporated into the chemical structure of BBGs to enhance their biological functionalities and antimicrobial properties. It was demonstrated that those ions play a crucial role in the biological responsiveness in vitro and in vivo once in contact with a physiological environment. The dissolution products of ion-doped BBGs were noted in their ability to stimulate gene expression related to cell differentiation and proliferation, promote angiogenesis, display anti-inflammatory effects, and inhibit bacterial growth within a few hours. Thus, metal-ion-doped BBGs address several limitations encountered by biomedical, tissue engineering, and infection control applications. Considering the research studies on BBGs to date, this review aims to analyze metal-ion-doped BBGs based on their primary antibacterial properties and effectiveness.

Material and technique fundamentals of nano-hydroxyapatite coatings towards biofunctionalization: a review

Hydroxyapatite (HAp) nanocoatings on titanium alloys (e.g. Ti6Al4V) have been used for prosthetic orthopaedic implants in recent decades because of their osseointegration, bioactivity, and biocompatibility. HAp is brittle with low mechanical strength and poor adhesion to metallic surfaces, which limits its durability and bioactivity. Surface modification techniques have alleviated the imperfections in biomaterials by coating the substrate. Several methods for improving the characteristics of implants, such as physical vapour deposition, the thermal spray method, the sol-gel method, microarc oxidation, and electrochemical deposition methods, have been discussed in this review. These processes provide mechanical strength without sacrificing biocompatibility and may lead to the development of new ideas for future research. This review discusses various selective additives, including carbon allotropes, ceramic materials, metallic materials, and multiple materials, to enhance tribological characteristics, biocompatibility, wear resistance, and mechanical strength. This review focuses on the fabrication of nano-HAps as coatings using selective deposition methods with controlled deposition parameters, paying special attention to recent developments in bone tissue engineering. This report is organized in such a way that it may inspire further research on surface modifications during medical treatment. The present review may help prospective investigators understand the importance of surface modifications for obtaining excellent implantation performance.

Green Synthesis of Multi-Walled Carbon Nanotube-Reinforced Hydroxyapatite Doped with Silver and Silver-Core Selenium-Shell Nanoparticles: Synthesis, Characterization, and Biological Activity

Hydroxyapatite (HAp) is widely used in biomedical applications due to its biocompatibility, osteoconductivity, and bioactivity. However, its low mechanical strength, tendency toward rapid corrosion, and lack of bactericidal properties present significant limitations in applications. This study aimed to improve the properties of HAp by reinforcing it with multi-walled carbon nanotubes (MWCNTs) and doping it with silver nanoparticles (AgNPs) and silver-core selenium-shell nanoparticles (Ag@SeNPs). Ocimum basilicum extract was used as both a reducing and stabilizing agent in the synthesis of nanoparticles using an environmentally friendly and non-toxic method as an alternative to traditional methods. The synthesized HAp, HAp/MWCNT, Ag-HAp/MWCNT, and Ag@Se-HAp/MWCNT nanocomposites were characterized by TEM, SEM, XRD, Raman spectroscopy, and BET analysis. BET analysis showed a reduction in surface area from 109.4 m2/g for pure HAp to 71.4 m2/g, 47.5 m2/g, and 35.3 m2/g for HAp/MWCNTs, Ag- HAp/MWCNTs, and Ag@Se-HAp/MWCNTs, respectively. Antimicrobial activities against P. aeruginosa, E. coli, S. aureus, E. faecalis, and C. albicans were evaluated. HAp and HAp/MWCNT did not show any antimicrobial activity, while Ag-HAp/MWCNTs showed inhibition zones of 14 mm for Escherichia coli and 18 mm for Pseudomonas aeruginosa at 5 mg/mL. Ag@Se-MWCNTs/HAp exhibited superior efficacy with inhibition zones of 18 mm, 12 mm, and 20 mm for S. aureus, E. faecalis, and Candida albicans, respectively. The incorporation of Ag@SeNPs enhanced HAp's antibacterial and antifungal properties through a synergistic mechanism.

Biomaterials for bone tissue engineering: achievements to date and future directions

Advancement in medicine and technology has resulted into prevention of countless deaths and increased life span. However, it is important to note that, the modern lifestyle has altered the food habits, witnessed increased life-style stresses and road accidents leading to several health complications and one of the primary victims is the bone health. More often than ever, healthcare professionals encounter cases of massive bone fracture, bone loss and generation of critical sized bone defects. Surgical interventions, through the use of bone grafting techniques are necessary in such cases. Natural bone grafts (allografts, autografts and xenografts) however, have major drawbacks in terms of delayed rehabilitation, lack of appropriate donors, infection and morbidity that shifted the focus of several investigators to the direction of synthetic bone grafts. By employing biomaterials that are based on bone tissue engineering (BTE), synthetic bone grafts provide a more biologically acceptable approach to establishing the phases of bone healing. In BTE, various materials are utilized to support and enhance bone regeneration. Biodegradable polymers like poly-(lactic acid), poly-(glycolic acid), and poly-(ϵ-caprolactone) are commonly used for their customizable mechanical properties and ability to degrade over time, allowing for natural bone growth. PEG is employed in hydrogels to promote cell adhesion and growth. Ceramics, such as hydroxyapatite and beta-tricalcium phosphate (β-TCP) mimic natural bone mineral and support bone cell attachment, withβ-TCP gradually resorbing as new bone forms. Composite materials, including polymer-ceramic and polymer-glasses, combine the benefits of both polymers and ceramics/glasses to offer enhanced mechanical and biological properties. Natural biomaterials like collagen, gelatin, and chitosan provide a natural matrix for cell attachment and tissue formation, with chitosan also offering antimicrobial properties. Hybrid materials such as decellularized bone matrix retain natural bone structure and biological factors, while functionalized scaffolds incorporate growth factors or bioactive molecules to further stimulate bone healing and integration. The current review article provides the critical insights on several biomaterials that could yield to revolutionary improvements in orthopedic medical fields. The introduction section of this article focuses on the statistical information on the requirements of various bone scaffolds globally and its impact on economy. In the later section, anatomy of the human bone, defects and diseases pertaining to human bone, and limitations of natural bone scaffolds and synthetic bone scaffolds were detailed. Biopolymers, bioceramics, and biometals-based biomaterials were discussed in further depth in the sections that followed. The article then concludes with a summary addressing the current trends and the future prospects of potential bone transplants.

Composites formed by layered double hydroxides with inorganic compounds: An overview of the synthesis methods and characteristics

Nowadays, layered double hydroxides (LDH), sometimes referred as hydrotalcite-like compounds, have gained great attention since their composition and structure can be easily modified, so that they can be implemented in multiple fields. LDH-based composite materials based on LDH exhibit tremendously improved properties such as high specific surface area, which promotes the accessibility to a greater number of LDH active sites, considerably improving their catalytic, adsorbent and biological activities. Therefore, this review summarizes and discusses the synthesis methods of composites constituted by LDH with other inorganic compounds such as zeolites, cationic clays, hydroxyapatites, among many others, and describe the resulting characteristics of the resulting composites, emphasizing the morphology. Brief descriptions of their properties and applications are also included.

Phosphate Ion-Responsive and Calcium Peroxide-Based Nanomedicine for Bone-Targeted Treatment of Breast Cancer Bone Metastasis

The treatment of breast cancer bone metastasis is an unresolved clinical challenge, mostly because currently therapeutic approaches cannot simultaneously block the tumor growth and repair the osteolytic bone injuries at the metastatic site. Herein, the study develops a novel nanomedicine to treat breast cancer bone metastasis. The nanomedicine is based on phosphate ion-responsive and calcium peroxide-based nanoparticles carrying the bone-targeting agent zoledronic acid on the surface and loaded with the photosensitizer indocyanine green. Following intravenous administration to a mouse model of breast cancer bone metastasis, the nanoparticles efficiently accumulate at the bone metastasis site, react with free phosphate ions, and form hydroxyapatite nanoaggregates and O2, while releasing the photosensitizer. Hydroxyapatite nanoaggregates elicit the remineralization of the collagenous bone matrix and trigger tumor cell apoptosis. Upon irradiating tumor-bearing legs with an 808 nm laser source, the O2 and free photosensitizer produced 1O2 by the reaction of the nanoparticles with phosphate ions, further boosting the anti-tumor effect. Tumor killing hampers the vicious cycle at the site of bone metastasis, translating to osteolysis blockade and further encouraging the remineralization of bone matrix. This work sheds light on the development of a novel, safe, and efficient approach for the treatment of breast cancer bone metastasis.

Study on porous coral scaffolds containing a hydroxyapatite layer doped with selenium and their properties

The repair of bone defects caused by osteosarcoma is still a significant clinical issue, and new scaffolds need to be developed to solve this problem. The ocean is a treasure trove for developing new biomedical materials, and coral is widely thought to be suitable as a scaffold for bone implant materials due to its porous structure and mechanical properties. Selenium is known for its antioxidant and antitumor effects, inducing tumor cell cycle arrest. In this study, we hydrothermally transformed corals to grow a hydroxyapatite layer on the scaffold surface (CHAp) and combined it with selenium to obtain selenium-doped scaffolds (Se-CHAp) without affecting the porous structure of the coral. The research successfully validates their biocompatibility and the antitumor efficacy against 143B osteosarcoma cells. The results indicate that the Se-CHAp scaffolds yielded an obvious inhibitory effect on the proliferation of osteosarcoma cells, highlighting that they have huge prospects for application in biomedical technology.

Evaluation of mineral induction ability and cytotoxicity of carbonated hydroxyapatite for pulp tissue regeneration: an in vitro study

Objectives

This study aimed to evaluate carbonated hydroxyapatite (CHA)'s ability for mineral induction and its in vitro cytotoxicity with human dental pulp cells.

Materials and Methods

Precursors for the study include di-ammonium hydrogen phosphate and calcium nitrate tetrahydrate, with sodium hydrogen carbonate added to achieve different levels of carbonate substitution. The synthesized CHA samples are characterized using X-ray diffraction, Fourier transform infrared spectroscopy, and Raman spectroscopy. Scanning electron microscopy (SEM) was used to observe morphology. For 14 days at 37°C, samples were submerged in simulated body fluid to assess their mineral induction capabilities. SEM was used to confirm apatite formation on sample surfaces. The cytotoxicity assay was used to assess the vitality of the cells following their exposure to various concentrations of CHA.

Results

The Joint Committee on Powder Diffraction Standards data for HA aligned well with the results from X-ray diffraction analysis of CHA across 3 different concentrations, indicating strong agreement. Fourier transform infrared spectra indicated the presence of phosphate, hydroxyl, and carbonate groups within the samples. SEM and Energy-dispersive X-ray analysis show agglomerated and flaky nanoparticles. All the samples are bioactive, but the formation of apatite differs from one another. In vitro cytotoxicity assay showed that over 70% of cells maintain viability.

Conclusions

The results of this study may provide insight into the potential use of carbonated HA as a dental pulp-capping material for vital pulp therapy.

Direct Immobilization of Folic Acid Molecules on Hydroxyapatite Nanoparticles with Substitution and Coordination Phenomena

We successfully synthesized folic acid (FA) immobilized hydroxyapatite (HA) nanoparticles without using a mediative reagent (e.g., silane coupling agent), and the immobilization states were evaluated and discussed. The HA nanoparticles with higher biocompatibility have two different planes, namely, c- and m-planes. These plane surfaces are rich in phosphate groups (P-site) and Ca2+ ions (C-site), respectively. We suggested that during the synthesis of the HA nanoparticles, the P-site substitution and C-site coordination with the addition of organic molecules containing -COO- ions can occur. Thus, it is possible to simultaneously immobilize two molecules to one HA nanoparticle. In this study, we successfully synthesized FA-immobilized HA nanoparticles by P-site substitution and C-site coordination reactions, which were named as substitution type and coordination type. In the substitution type, when FA was reacted with HA during the nucleation stage, the PO43- ions of HA decreased as the FA ratio of coverage surface area increased, and the crystalline phase was changed significantly from the Ca deficient HA to the carbonated HA phase. Accordingly, it was indicated that FA was immobilized on HA by the P-site substitution. In the coordination type, since FA was reacted with HA after the completion of crystal growth, the crystalline phase was changed slightly as the FA ratio of coverage surface area increased, indicating that FA was immobilized on HA by the C-site coordination. From the above, we controlled the FA immobilization states on the HA nanoparticles by the P-site substitution and the C-site coordination through the FA addition timing in the synthesis. Since the -COO- ions in FA could be selectively substituted with the P-site in HA, it is possible to directly coordinate the foreign organic molecules to the Ca2+ ions in HA. Therefore, the immobilization technique of this study is expected to achieve two different drug molecules with diagnosis and therapy functions (i.e., theranostics) on one nanoparticle.

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.

Bottom-Up Assembling Hierarchical Enamel-Like Bulk Materials with Excellent Optical and Mechanical Properties for Tooth Restoration

Enamel has good optical and mechanical properties because of its multiscale hierarchical structure. Biomimetic construction of enamel-like 3D bulk materials at nano-, micro-, mesh- and macro-levels is a challenge. A novel facile, cost-effective, and easy large-scale bottom-up assembly strategy to align 1D hydroxyapatite (HA) nanowires bundles to 3D hierarchical enamel structure with the nanowires bundles layer-by-layer interweaving orientation, is reported. In the strategy, the surface of oleate templated ultralong HA nanowires with a large aspect ratio is functionalized with amphiphilic 10-methacryloyloxydecyl dihydrogen phosphate (MDP). Furtherly, the MDP functionalized HA nanowire bundles are assembled layer-by-layer with oriented fibers in a single layer and cross-locked between layers at a certain angle at mesoscale and macroscale in the viscous bisphenol A-glycidyl methacrylate (Bis-GMA) ethanol solution by shear force induced by simple agitation and high-speed centrifugation. Finally, the excessive Bis-GMA and ethanol are removed, and (Bis-GMA)-(MDP-HA nanowire bundle) matrix is densely packed under hot pressing and polymerized to form bulk enamel-like materials. The composite has superior optical properties and comparable comprehensive mechanic performances through a combination of strength, hardness, toughness, and friction. This method may open new avenues for controlling the nanowires assembly to develop hierarchical nanomaterials with superior properties for many different applications.

Laponite nanoclay loaded microgel suspensions as supportive matrices for osteogenesis

Microscale carriers have emerged as promising materials for nurturing cell growth and as delivery vehicles for regenerative therapies. Carriers based on hydrogels have proved advantageous, where "microgels" can be formulated to have a broad range of properties to guide the behavior of adherent cells. Here we demonstrate the fabrication of osteogenic microgels through incorporation of laponite nanoclays. Forming a jammed suspension provides a scaffolding where cells can adhere to the surface of the microgels, with pathways for migration and proliferation fostered by the interstitial volume. By varying the content and type of laponite-RD and XLG-the degree of osteogenesis can be tuned in embedded populations of adipose derived stem cells (ADSCs). The nano- micro-structured composite materials enhance osteogenesis at the transcript and protein level, leading to increased deposition of bone minerals and an increase in the compressive modulus of the assembled scaffold. Together, these microgel suspensions are promising materials for encouraging osteogenesis with scope for delivery via syringe injection and stabilization to bone-mimetic mechanical properties after matrix deposition.

Chondroitin Sulfate-Modified Hydroxyapatite for Caspase-1 Activated Induced Pyroptosis through Ca Overload/ER Stress/STING/IRF3 Pathway in Colorectal Cancer

Immune checkpoint inhibitors, are the fourth most common therapeutic tool after surgery, chemotherapy, and radiotherapy for colorectal cancer (CRC). However, only a small proportion (≈5%) of CRC patients, those with "hot" (immuno-activated) tumors, benefit from the therapy. Pyroptosis, an innovative form of programmed cell death, is a potentially effective means to mediate a "cold" to "hot" transformation of the tumor microenvironment (TME). Calcium-releasing hydroxyapatite (HAP) nanoparticles (NPs) trigger calcium overload and pyroptosis in tumor cells. However, current limitations of these nanomedicines, such as poor tumor-targeting capabilities and insufficient calcium (Ca) ion release, limit their application. In this study, chondroitin sulfate (CS) is used to target tumors via binding to CD44 receptors and kaempferol (KAE) is used as a Ca homeostasis disruptor to construct CS-HAP@KAE NPs that function as pyroptosis inducers in CRC cells. CS-HAP@KAE NPs bind to the tumor cell membrane, HAP released Ca in response to the acidic environment of the TME, and kaempferol (KAE) enhances the influx of extracellular Ca, resulting in intracellular Ca overload and pyroptosis. This is associated with excessive endoplasmic reticulum stress triggered activation of the stimulator of interferon genes/interferon regulatory factor 3 pathway, ultimately transforming the TME from "cold" to "hot".

Electrospun polyvinyl alcohol nanofiber scaffolds incorporated strontium-substituted hydroxyapatite from sand lobster shells: synthesis, characterization, and in vitro biological properties

The paper describes the synthesis of hydroxyapatite (HAp) and strontium-substituted hydroxyapatite (SrHAp) from sand lobster shells by a hydrothermal method. The HAp and SrHAp were incorporated into the polyvinyl alcohol (PVA) nanofiber scaffold through the eletrospinning method. The scaffolds were incorporated with 5wt% of hydroxyapatite (HAp), 5wt%, 10wt%, and 15% of SrHAp. The physicochemical, mechanical, and in vitro biological properties of the scaffold were evaluated. The incorporation of HAp or SrHAp was evidenced by the diffraction patterns and the phosphate functional groups related to HAp. The morphological results showed the decrement of fiber diameter in line with the increased SrHAp concentration. A tensile test was conducted to investigate the mechanical properties of the scaffolds, and the results showed that the scaffolds perform poorly at a higher SrHAp concentration because of exceeding agglomeration levels. The PVA/SrHAp15 performed the best antibacterial activity against E. coli and S. aureus with an inhibition zone of (15.2 ± 0.2) and (14.5 ± 0.8), respectively. The apatite formation was more abundant in PVA/SrHAp10 after immersion in a simulated body fluid (SBF). Cell viability results showed that the scaffold enabled the osteoblast cells to grow and proliferate. The biocompatibility of HAp and SrHAp resulted in the enhancement of cell adhesion. Based on all tests, the PVA/SrHAp 10 scaffold shows a strong candidate for further in vivo studies.

Synthesis, Characterization, and Biological Performances of Magnesium-Substituted Dicalcium Phosphate Anhydrous

Dicalcium phosphate anhydrous (DCPA, CaHPO4) is regarded as an orthopedic material due to its ability to match the generation of new bone to the rate of implant resorption without considering the material's mechanical stability. Additionally, magnesium (Mg) is widely recognized for its essential function in bone metabolism, especially during the initial phases of osteogenesis. Therefore, we explored the influences of Mg ions on DCPA powder, in biological responses, and on the enhancement of osteogenic properties. Mg-DCPA powders with varying substitution levels (0, 3, 5, and 7 mol%) were produced using the co-precipitation method. In the in vitro test, precipitates began to develop on the surface of the Mg-DCPA powders after 7 days. These results indicate that Mg ions in the DCPA powder could enhance the generation of a new apatite phase when subjected to physiological fluids on the surface of the powder. In addition, the osteogenic performance of the DCPA powder was improved by adding Mg ions. The most effective magnesium substitution content in the DCPA powder in order to improve its osteogenic potential was approximately 3 mol%. Consequently, this amount of magnesium in the DCPA powder could control the maintaining time in the implantation operation to produce a new apatite phase.

Bactericidal behavior of silver nanoparticle decorated nano-sized magnetic hydroxyapatite

Methicillin-resistant Staphylococcus aureus (MRSA) is the most common cause of acute bacterial arthritis. Due to the increase in antibiotic resistance in these bacteria, the discovery of new antibacterial agents has become one of the hot topics in the scientific community. Here, we prepared a nano-sized porous biocompatible magnetic hydroxyapatite through a solvothermal method. Then, we adopted a post-synthesis modification strategy to modify its surface for the stabilization of Ag NPs through a green reduction by the euphorbia plant extract. Moreover, the results show that the prepared composite perfectly prevents the aggregation of Ag NPs. This composite was used as a bactericidal and antibiofilm agent against MRSA bacteria in an in vitro environment, which showed excellent results. Also, the cell viability assay indicates that the prepared composite has low cytotoxicity, making it a perfect antibacterial agent for in vivo experiments.

3D printed scaffolds of biosilica and spongin from marine sponges: analysis of genotoxicity and cytotoxicity for bone tissue repair

Biosilica (BS) and spongin (SPG) from marine sponges are highlighted for their potential to promote bone regeneration. Moreover, 3D printing is introduced as a technology for producing bone grafts with optimized porous structures, allowing for better cell attachment, proliferation, and differentiation. Thus, this study aimed to characterize the BS and BS/SPG 3D printed scaffolds and to evaluate the biological effects in vitro. The scaffolds were printed using an ink containing 4 wt.% of sodium alginate. The physicochemical characteristics of BS and BS/SPG 3D printed scaffolds were analyzed by SEM, EDS, FTIR, porosity, evaluation of mass loss, and pH measurement. For in vitro analysis, the cellular viability of the MC3T3-E1 cell lineage was assessed using the AlamarBlue® assay and confocal microscopy, while genotoxicity and mineralization potential were evaluated through the micronucleus assay and Alizarin Red S, respectively. SEM analysis revealed spicules in BS, the fibrillar structure of SPG, and material degradation over the immersion period. FTIR indicated peaks corresponding to silicon oxide in BS samples and carbon oxide and amine in SPG samples. BS-SPG scaffolds exhibited higher porosity, while BS scaffolds displayed greater mass loss. pH measurements indicated a significant decrease induced by BS, which was mitigated by SPG over the experimental periods. In vitro studies demonstrated the biocompatibility and non-cytotoxicity of scaffold extracts. .Also, the scaffolds promoted cellular differentiation. The micronucleus test further confirmed the absence of genotoxicity. These findings suggest that 3D printed BS and BS/SPG scaffolds may possess desirable morphological and physicochemical properties, indicating in vitro biocompatibility.

Biomimetic Scaffolds of Calcium-Based Materials for Bone Regeneration

Calcium-based materials, such as calcium carbonate, calcium phosphate, and calcium silicate, have attracted significant attention in biomedical research, owing to their unique physicochemical properties and versatile applications. The distinctive characteristics of these materials, including their inherent biocompatibility and tunable structures, hold significant promise for applications in bone regeneration and tissue engineering. This review explores the biomedical applications of calcium-containing materials, particularly for bone regeneration. Their remarkable biocompatibility, tunable nanostructures, and multifaceted functionalities make them pivotal for advancing regenerative medicine, drug delivery system, and biomimetic scaffold applications. The evolving landscape of biomedical research continues to uncover new possibilities, positioning calcium-based materials as key contributors to the next generation of innovative biomaterial scaffolds.

Hydroxyapatite-Based Natural Biopolymer Composite for Tissue Regeneration

Hydroxyapatite (HAp) polymer composites have gained significant attention due to their applications in bone regeneration and tooth implants. This review examines the synthesis, properties, and applications of Hap, highlighting various manufacturing methods, including wet, dry, hydrothermal, and sol-gel processes. The properties of HAp are influenced by precursor materials and are commonly obtained from natural calcium-rich sources like eggshells, seashells, and fish scales. Composite materials, such as cellulose-hydroxyapatite and gelatin-hydroxyapatite, exhibit promising strength and biocompatibility for bone and tissue replacement. Metallic implants and scaffolds enhance stability, including well-known titanium-based and stainless steel-based implants and ceramic body implants. Biopolymers, like chitosan and alginate, combined with Hap, offer chemical stability and strength for tissue engineering. Collagen, fibrin, and gelatin play crucial roles in mimicking natural bone composition. Various synthesis methods like sol-gel, hydrothermal, and solution casting produce HAp crystals, with potential applications in bone repair and regeneration. Additionally, the use of biowaste materials, like eggshells and snails or seashells, not only supports sustainable HAp production but also reduces environmental impact. This review emphasizes the significance of understanding the properties of calcium-phosphate (Ca-P) compounds and processing methods for scaffold generation, highlighting novel characteristics and mechanisms of biomaterials in bone healing. Comparative studies of these methods in specific applications underscore the versatility and potential of HAp composites in biomedical engineering. Overall, HAp composites offer promising solutions for improving patient outcomes in bone replacement and tissue engineering and advancing medical practices.

Collagen-hydroxyapatite based scaffolds for bone trauma and regeneration: recent trends and future perspectives

Regenerative therapy, a key area of tissue engineering, holds promise for restoring damaged organs, especially in bone regeneration. Bone healing is natural to the body but becomes complex under stress and disease. Large bone deformities pose significant challenges in tissue engineering. Among various methods, scaffolds are attractive as they provide structural support and essential nutrients for cell adhesion and growth. Collagen and hydroxyapatite (HA) are widely used due to their biocompatibility and biodegradability. Collagen and nano-scale HA enhance cell adhesion and development. Thus, nano HA/collagen scaffolds offer potential solutions for bone regeneration. This review focuses on the use and production of nano-sized HA/collagen composites in bone regeneration.

Synthetic or Natural (Bio-Based) Hydroxyapatite? A Systematic Comparison between Biomimetic Nanostructured Coatings Produced by Ionized Jet Deposition

Calcium phosphate (CaP)-based materials are largely explored in orthopedics, to increase osseointegration of the prostheses and specifically in spine surgery, to permit better fusion. To address these aims, nanostructured biogenic apatite coatings are emerging, since they better mimic the characteristics of the host tissue, thus potentially being better candidates compared to their synthetic counterpart. Here, we compare hydroxyapatite (HA) nanostructured coatings, obtained by ionized jet deposition, starting from synthetic and natural sources. The starting materials and the corresponding films are characterized and compared from a compositional and morphological point of view, then their stability is studied after post-treatment annealing. Although all the films are formed by globular aggregates and show morphological features at different scales (from nano to micro), significant differences are found in composition between the synthetic and naturally derived HA in terms of magnesium and sodium content, carbonate substitution and Ca/P ratio, while differences between the coatings obtained by the different natural HA sources are minor. In addition, the shape of the aggregates is also target-dependent. All coatings have a good stability after over 14 days of immersion in medium, with natural apatite coatings showing a better behavior, as no cracking and detachments are observed during immersion. Based on these results, both synthetic and naturally derived apatitic materials appear promising for applications in spine surgery, with coatings from natural sources possessing physiochemical properties more similar to the mineral phase of the human bone tissue.

Characterization and Comparative Investigation of Hydroxyapatite/Carboxymethyl Cellulose (CaHA/CMC) Matrix for Soft Tissue Augmentation in a Rat Model

This study endeavors to develop an injectable subdermal implant material tailored for soft tissue repair and enhancement. The material consists of a ceramic phase of calcium hydroxyapatite (CaHA), which is biocompatible, 20-60 μm in size, known for its biocompatibility and minimal likelihood of causing foreign body reactions, antigenicity, and minimal inflammatory response, dispersed in a carrier phase composed of carboxymethyl cellulose (CMC), glycerol, and water for injection. The gel formulation underwent comprehensive characterization via various analytical techniques. X-ray diffraction (XRD) was employed to identify crystalline phases and investigate the structural properties of ceramic particles, while thermogravimetric analysis (TGA) was conducted to evaluate the thermal stability and decomposition behavior of the final formulation. Scanning electron microscopy (SEM) was utilized to examine the surface morphology and particle size distribution, confirming the homogeneous dispersion of spherical CaHA particles within the matrix. SEM analysis revealed particle sizes ranging from approximately 20-60 μm. Elemental analysis confirmed a stoichiometric Ca/P ratio of 1.65 in the hydroxyapatite (HA) structure. Heavy metal content exhibited suitability for surgical implant use without posing toxicity risks. Rheological analysis revealed a storage modulus of 58.6 and 68.9 kPa and a loss modulus of 21.7 and 24.8 kPa at the frequencies of 2 and 5 Hz, respectively. 150 μL of sterilized CaHA/CMC was injected subcutaneously into rats and compared with a similar product, Crystalys, to assess its effects on soft tissues. Skin tissue samples of rats were collected at specific intervals throughout the study (30, 45, 60, 90 and 120 days), and examined histologically. Results demonstrated that CaHA/CMC gel led to a significant increase in dermal thickness, elastic fibers, and collagen density. Based on the findings, the formulated CaHA/CMC gel was found to be biocompatible, biodegradable, nonimmunogenic, nontoxic, safe, and effective, and represents a promising option for soft tissue repair and augmentation.

Evaluation of the remineralization potential of self-assembling peptide P11-4 with fluoride compared to fluoride varnish in the management of incipient carious lesions: a randomized controlled clinical trial

OBJECTIVES

The present trial's aim was to compare the remineralization potential of self-assembling peptide P11-4 combined with fluoride to that of fluoride varnish.

MATERIALS AND METHODS

Twenty-eight participants with 58 incipient carious lesions were enrolled in the present trial. Participants were randomly divided into two groups with 14 participants and 29 incipient lesions in each group. Patients were assigned either to self-assembling peptide combined with fluoride (Curodont Repair Fluoride Plus™) or sodium fluoride varnish (NaF, Bifluorid 10) groups. Both agents were applied according to the manufacturer's instructions on non-cavitated incipient carious lesions. Lesions were assessed by two calibrated and blinded assessors at baseline, and after one-, three- and six-months using a laser fluorescence device (DIAGNOdent).

RESULTS

Although laser fluorescence scores significantly improved in both groups over time (p < 0.05), no notable differences were evident between both groups at one-month (p > 0.05). Yet, at three- and six-months statistically lower laser fluorescence readings were evident in the self-assembling peptide combined with fluoride group in comparison to the fluoride alone group (p < 0.05). There was 60% less risk for caries progression for Curodont Repair Fluoride Plus™ when compared to NaF varnish after six months. Self-assembling peptide combined with fluoride was able to change 65.5% of non-cavitated carious lesions from DIAGNOdent score 3 (11-20) to score 1 (0-4). Fluoride varnish was able to change 13.8% of the lesions from score 3 to score 1 after six months.

CONCLUSIONS

The self-assembling peptide combined with fluoride varnish showed higher remineralization potential than fluoride varnish alone for incipient carious lesions over a six-months follow up.

CLINICAL RELEVANCE

The combination of self-assembling peptide P11-4 and fluoride could offer a new tool in managing incipient carious lesions.

Initial solution pH value for the construction of a 3D hydroxyapatite via the trisodium citrate-assisted hydrothermal route

In this study, a trisodium citrate (TSC)-assisted hydrothermal method is utilized to prepare three-dimensional hydroxyapatite (3D HA). Understanding the role of TSC in the preparation of 3D HA crystals may provide valuable methods to design advanced biomaterials. As one of the indexes of solution supersaturation, the initial pH (ipH) value can not only directly affect the nucleation rate, but also affect the growth of HA crystals. In this work, the effect of the ipH on the microstructure, particle size distribution, and specific surface area of the 3D HA is explored. Results showed that the morphology of 3D HA transformed from a bundle to a dumbbell ball and then a dumbbell with an increase in the ipH. A corresponding mechanism of such a structural evolution was proposed, providing inspiration for the fabrication of innovative 3D HA structures with enhanced biological functionality and performance.

Biodegradable polyvinyl alcohol/nano-hydroxyapatite composite membrane enhanced by MXene nanosheets for guided bone regeneration

MXene, as a new category of two-dimensional nanomaterials, exhibits a promising prospect in biomedical applications due to its ultrathin structure and morphology, as well as a range of remarkable properties such as biological, chemical, electronic, and optical properties. In this work, different concentrations of MXene (M) were added to polyvinyl alcohol (PVA, P)/nano-hydroxyapatite (n-HA, H) mixed solution, and series of PVA/n-HA/MXene (PHM) composite membranes were obtained by combining sol-gel and freeze-drying processes. Morphology, chemical composition, surface, and mechanical properties of the prepared PHM membranes were characterized by various techniques. Subsequently, the swelling and degradation performances of the composite membranes were tested by swelling and degradation tests. In addition, in vitro studies like cell adhesion, cytotoxicity, proliferation, osteogenic differentiation, and antibacterial properties of MC3T3-E1 were also evaluated. The results showed that the addition of MXene could apparently improve the composite membranes' physicochemical properties, bioactivity, and osteogenic differentiation. Specially, PHM membrane had the best comprehensive properties when the concentration of MXene was set as 2.0% w/v. In a word, the addition of MXene has a positive effect on improving the mechanical properties, osteogenic induction, and antibacterial properties of PH composite membranes, and the prepared PHM composite membranes possess potential applications for guided bone regeneration.

Gradient gyroid Ti6Al4V scaffolds with TiO2 surface modification: Promising approach for large bone defect repair

Large bone defects, particularly those exceeding the critical size, present a clinical challenge due to the limited regenerative capacity of bone tissue. Traditional treatments like autografts and allografts are constrained by donor availability, immune rejection, and mechanical performance. This study aimed to develop an effective solution by designing gradient gyroid scaffolds with titania (TiO2) surface modification for the repair of large segmental bone defects. The scaffolds were engineered to balance mechanical strength with the necessary internal space to promote new bone formation and nutrient exchange. A gradient design of the scaffold was optimized through Finite Element Analysis (FEA) and Computational Fluid Dynamics (CFD) simulations to enhance fluid flow and cell adhesion. In vivo studies in rabbits demonstrated that the G@TiO2 scaffold, featuring a gradient structure and TiO2 surface modification, exhibited superior healing capabilities compared to the homogeneous structure and TiO2 surface modification (H@TiO2) and gradient structure (G) scaffolds. At 12 weeks post-operation, in a bone defect representing nearly 30 % of the total length of the radius, the implantation of the G@TiO2 scaffold achieved a 27 % bone volume to tissue volume (BV/TV) ratio, demonstrating excellent osseointegration. The TiO2 surface modification provided photothermal antibacterial effects, enhancing the scaffold's biocompatibility and potential for infection prevention. These findings suggest that the gradient gyroid scaffold with TiO2 surface modification is a promising candidate for treating large segmental bone defects, offering a combination of mechanical strength, bioactivity, and infection resistance.

Advanced applications of hydroxyapatite nanocomposite materials for heavy metals and organic pollutants removal by adsorption and photocatalytic degradation: A review

This comprehensive review delves into the forefront of scientific exploration, focusing on hydroxyapatite-based nanocomposites (HANCs) and their transformative role in the adsorption of heavy metals (HMs) and organic pollutants (OPs). Nanoscale properties, including high surface area and porous structure, contribute to the enhanced adsorption capabilities of HANCs. The nanocomposites' reactive sites facilitate efficient contaminant interactions, resulting in improved kinetics and capacities. HANCs exhibit selective adsorption properties, showcasing the ability to discriminate between different contaminants. The eco-friendly synthesis methods and potential for recyclability position the HANCs as environmentally friendly solutions for adsorption processes. The review acknowledges the dynamic nature of the field, which is characterized by continuous innovation and a robust focus on ongoing research endeavors. The paper highlights the HANCs' selective adsorption capabilities of various HMs and OPs through various interactions, including hydrogen and electrostatic bonding. These materials are also used for aquatic pollutants' photocatalytic degradation, where reactive hydroxyl radicals are generated to oxidize organic pollutants quickly. Future perspectives explore novel compositions, fabrication methods, and applications, driving the evolution of HANCs for improved adsorption performance. This review provides a comprehensive synthesis of the state-of-the-art HANCs, offering insights into their diverse applications, sustainability aspects, and pivotal role in advancing adsorption technologies for HMs and OPs.

Strategies to improve the performance of polyetheretherketone (PEEK) as orthopedic implants: from surface modification to addition of bioactive materials

Polyetheretherketone (PEEK), as a high-performance polymer, is widely used for bone defect repair due to its homogeneous modulus of elasticity of human bone, good biocompatibility, excellent chemical stability and projectability. However, the highly hydrophobic surface of PEEK is biologically inert, which makes it difficult for cells and proteins to attach, and is accompanied by the development of infections that ultimately lead to failure of PEEK implants. In order to further enhance the potential of PEEK as an orthopedic implant, researchers have explored modification methods such as surface modification by physical and chemical means and the addition of bioactive substances to PEEK-based materials to enhance the mechanical properties, osteogenic activity and antimicrobial properties of PEEK. However, these current modification methods still have obvious shortcomings in terms of cost, maneuverability, stability and cytotoxicity, which still need to be explored by researchers. This paper reviews some of the modification methods that have been used to improve the performance of PEEK over the last three years in anticipation of the need for researchers to design PEEK orthopedic implants that better meet clinical needs.

Probing the influence of strontium doping and annealing temperature on the structure and biocompatibility of hydroxyapatite nanorods

Among numerous biologically important metal cations, strontium (Sr2+) has received much attention in bone tissue regeneration because of its osteoinductive properties combined with its ability to inhibit osteoclast activity. In this study, strontium-doped hydroxyapatite (Sr-HAp) nanorods with varying molar ratios of Ca : Sr (10 : 0, 9 : 1, 5 : 5, 3 : 7 and 0 : 10) were synthesized using the chemical precipitation technique. The synthesized Sr-HAp nanostructures were characterized using powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy, energy dispersive X-ray spectroscopy, and Raman and Fourier transform infrared (FTIR) spectroscopies to understand their structural and morphological features, and composition. XRD results revealed the formation of HAp nanostructures, whose unit cell volume increased as a function of the dopant level. The reaction process investigation showed the formation of hydroxyapatite (HAp), strontium apatite (SAp) and various Sr-HAp phases. FESEM micrographs displayed the morphological transformation of Sr-HAp from nanorods to nanosheets upon increasing the dopant level. In the FTIR spectra, the bands of the PO43- group shifted towards a lower wavenumber upon increasing the dopant concentration in Sr-HAp that signifies the structural distortion due to the presence of a large amount of strontium ions. The peaks of PO43- and OH- vibrations in the Raman spectra were further analysed to corroborate the structural distortion of Sr-HAp. Selected area electron diffraction patterns obtained using TEM reveal the reduced crystallinity of Sr-HAp due to Sr-doping, which is in line with the XRD results. Finally, the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay showed that the synthesized Sr-HAp has no toxic effect on the survival and growth of mesenchymal stem cells. In summary, the synthesized novel Sr-HAp nanorods exhibit great promise for bone tissue engineering applications.

Biominerals and Bioinspired Materials in Biosensing: Recent Advancements and Applications

Inspired by nature's remarkable ability to form intricate minerals, researchers have unlocked transformative strategies for creating next-generation biosensors with exceptional sensitivity, selectivity, and biocompatibility. By mimicking how organisms orchestrate mineral growth, biomimetic and bioinspired materials are significantly impacting biosensor design. Engineered bioinspired materials offer distinct advantages over their natural counterparts, boasting superior tunability, precise controllability, and the ability to integrate specific functionalities for enhanced sensing capabilities. This remarkable versatility enables the construction of various biosensing platforms, including optical sensors, electrochemical sensors, magnetic biosensors, and nucleic acid detection platforms, for diverse applications. Additionally, bioinspired materials facilitate the development of smartphone-assisted biosensing platforms, offering user-friendly and portable diagnostic tools for point-of-care applications. This review comprehensively explores the utilization of naturally occurring and engineered biominerals and materials for diverse biosensing applications. We highlight the fabrication and design strategies that tailor their functionalities to address specific biosensing needs. This in-depth exploration underscores the transformative potential of biominerals and materials in revolutionizing biosensing, paving the way for advancements in healthcare, environmental monitoring, and other critical fields.

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.

Enhancing Bone Implants: Magnesium-Doped Hydroxyapatite for Stronger, Bioactive, and Biocompatible Applications

Hydroxyapatite (HAp) with the chemical formula Ca10(PO4)6(OH)2 is an inorganic material that exhibits morphology and composition similar to those of human bone tissues, making it highly desirable for bone regeneration applications. As one of the most biocompatible materials currently in use, HAp has undergone numerous attempts to enhance its mechanical strength. This research focuses on investigating the influence of magnesium (Mg) incorporation on the structural and mechanical properties of synthesized magnesium-doped hydroxyapatite (MgHAp) samples. Apart from its biocompatibility, Mg possesses a density and elasticity comparable to those of human bone. Therefore, incorporating Mg into HAp can be pivotal for improving bone formation. Previous studies have not extensively explored the structural changes induced by Mg substitution in HAp, which motivated us to revisit this issue. Hydrothermal synthesis technique was used to synthesize MgHAp samples with varying molar concentrations (x = 0, 0.5, 1.0, and 1.5). Theoretical simulation of HAp and MgHAp for obtaining 3D structures has been done, and theoretical X-ray diffraction (XRD) data have been compared with the experimental XRD data. Rietveld analysis revealed the alteration and deviation of lattice parameters with an increase in the Mg content, which ultimately affect the structure as well the mechanical properties of prepared samples. The findings revealed an increase in compressive stress and fracture toughness as the Mg concentration in the composition increased. Furthermore, using a finite-element analysis technique and modeling of the mechanical testing data, the von Mises stress distribution and Young's modulus values were calculated, demonstrating the similarity of the prepared samples to human cortical bone. Biocompatibility assessments using NIH-3T3 fibroblast cells confirmed the biocompatible and bioactive nature of the synthesized samples. MgHAp exhibits great potential for biomedical applications in the dental, orthopedic, and tissue engineering research fields.

Wet 3D printing of biodegradable porous scaffolds to enable room-temperature deposition modeling of polymeric solutions for regeneration of articular cartilage

Tissue engineering has emerged as an advanced strategy to regenerate various tissues using different raw materials, and thus it is desired to develop more approaches to fabricate tissue engineering scaffolds to fit specific yet very useful raw materials such as biodegradable aliphatic polyester like poly (lactide-co-glycolide) (PLGA). Herein, a technique of 'wet 3D printing' was developed based on a pneumatic extrusion three-dimensional (3D) printer after we introduced a solidification bath into a 3D printing system to fabricate porous scaffolds. The room-temperature deposition modeling of polymeric solutions enabled by our wet 3D printing method is particularly meaningful for aliphatic polyester, which otherwise degrades at high temperature in classic fuse deposition modeling. As demonstration, we fabricated a bilayered porous scaffold consisted of PLGA and its mixture with hydroxyapatite for regeneration of articular cartilage and subchondral bone. Long-termin vitroandin vivodegradation tests of the scaffolds were carried out up to 36 weeks, which support the three-stage degradation process of the polyester porous scaffold and suggest faster degradationin vivothanin vitro. Animal experiments in a rabbit model of articular cartilage injury were conducted. The efficacy of the scaffolds in cartilage regeneration was verified through histological analysis, micro-computed tomography (CT) and biomechanical tests, and the influence of scaffold structures (bilayerversussingle layer) onin vivotissue regeneration was examined. This study has illustrated that the wet 3D printing is an alternative approach to biofabricate tissue engineering porous scaffolds based on biodegradable polymers.

Electrospun Fenoprofen/Polycaprolactone @ Tranexamic Acid/Hydroxyapatite Nanofibers as Orthopedic Hemostasis Dressings

Dressings with multiple functional performances (such as hemostasis, promoting regeneration, analgesia, and anti-inflammatory effects) are highly desired in orthopedic surgery. Herein, several new kinds of medicated nanofibers loaded with several active ingredients for providing multiple functions were prepared using the modified coaxial electrospinning processes. With an electrospinnable solution composed of polycaprolactone and fenoprofen as the core working fluid, several different types of unspinnable fluids (including pure solvent, nanosuspension containing tranexamic acid and hydroxyapatite, and dilute polymeric solution comprising tranexamic acid, hydroxyapatite, and polyvinylpyrrolidone) were explored to implement the modified coaxial processes for creating the multifunctional nanofibers. Their morphologies and inner structures were assessed through scanning and transmission electron microscopes, which all showed a linear format without the discerned beads or spindles and a diameter smaller than 1.0 μm, and some of them had incomplete core-shell nanostructures, represented by the symbol @. Additionally, strange details about the sheaths' topographies were observed, which included cracks, adhesions, and embedded nanoparticles. XRD and FTIR verified that the drugs tranexamic acid and fenoprofen presented in the nanofibers in an amorphous state, which resulted from the fine compatibility among the involved components. All the prepared samples were demonstrated to have a fine hydrophilic property and exhibited a lower water contact angle smaller than 40° in 300 ms. In vitro dissolution tests indicated that fenoprofen was released in a sustained manner over 6 h through a typical Fickian diffusion mechanism. Hemostatic tests verified that the intentional distribution of tranexamic acid on the shell sections was able to endow a rapid hemostatic effect within 60 s.

Enhancing osteoblast proliferation and bone regeneration by poly (amino acid)/selenium-doped hydroxyapatite

Among various biomaterials employed for bone repair, composites with good biocompatibility and osteogenic ability had received increasing attention from biomedical applications. In this study, we doped selenium (Se) into hydroxyapatite (Se-HA) by the precipitation method, and prepared different amounts of Se-HA-loaded poly (amino acid)/Se-HA (PAA/Se-HA) composites (0, 10 wt%, 20 wt%, 30 wt%) byin-situmelting polycondensation. The physical and chemical properties of PAA/Se-HA composites were characterized by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and their mechanical properties. XRD and FT-IR results showed that PAA/Se-HA composites contained characteristic peaks of PAA and Se-HA with amide linkage and HA structures. DSC and TGA results specified the PAA/Se-HA30 composite crystallization, melting, and maximum weight loss temperatures at 203.33 °C, 162.54 °C, and 468.92 °C, respectively, which implied good thermal stability. SEM results showed that Se-HA was uniformly dispersed in PAA. The mechanical properties of PAA/Se-HA30 composites included bending, compressive, and yield strengths at 83.07 ± 0.57, 106.56 ± 0.46, and 99.17 ± 1.11 MPa, respectively. The cellular responses of PAA/Se-HA compositesin vitrowere studied using bone marrow mesenchymal stem cells (BMSCs) by cell counting kit-8 assay, and results showed that PAA/Se-HA30 composites significantly promoted the proliferation of BMSCs at the concentration of 2 mg ml-1. The alkaline phosphatase activity (ALP) and alizarin red staining results showed that the introduction of Se-HA into PAA enhanced ALP activity and formation of calcium nodule. Western blotting and Real-time polymerase chain reaction results showed that the introduction of Se-HA into PAA could promoted the expression of osteogenic-related proteins and mRNA (integrin-binding sialoprotein, osteopontin, runt-related transcription factor 2 and Osterix) in BMSCs. A muscle defect at the back and a bone defect at the femoral condyle of New Zealand white rabbits were introduced for evaluating the enhancement of bone regeneration of PAA and PAA/Se-HA30 composites. The implantation of muscle tissue revealed good biocompatibility of PAA and PAA/Se-HA30 composites. The implantation of bone defect showed that PAA/Se-HA30 composites enhanced bone formation at the defect site (8 weeks), exhibiting good bone conductivity. Therefore, the PAA-based composite was a promising candidate material for bone tissue regeneration.

Disruption of Communication: Recent Advances in Antibiofilm Materials with Anti-Quorum Sensing Properties

Biofilm contamination presents a significant threat to public health, the food industry, and aquatic/marine-related applications. In recent decades, although various methods have emerged to combat biofilm contamination, the intricate and persistent nature of biofilms makes complete eradication challenging. Therefore, innovative alternative solutions are imperative for addressing biofilm formation. Instead of solely focusing on the eradication of mature biofilms, strategically advantageous measures involve the delay or prevention of biofilm formation on surfaces. Quorum sensing, a communication system enabling bacteria to coordinate their behavior based on population density, plays a pivotal role in biofilm formation for numerous microbial species. Materials possessing antibiofilm properties that target quorum sensing have gained considerable attention for their potential to prevent biofilm formation. This Review consolidates recent research progress on the utilization of materials with antiquorum sensing properties for combating biofilm formation. These materials can be categorized into three distinct types: (i) antibiofilm nanomaterials, (ii) antibiofilm surfaces, and (iii) antibiofilm hydrogels with antiquorum sensing capabilities. Finally, the Review concludes with a brief discussion of current challenges and outlines potential avenues for future research.

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.

Enhanced Adsorption Stability and Biofunction Durability with Phosphonate-Grafted, PEGylated Copolymer on Hydroxyapatite Surface

Nonfouling surfaces are crucial in applications such as biosensors, medical implants, marine coatings, and drug delivery vehicles. However, their long-term coating stability and robust surface binding strength in physiological media remain challenging. Herein, a phosphonate-grafted, PEGylated copolymer on the hydroxyapatite (HA) surface is proposed to significantly improve the adsorption stability and thus enhance the biofunction durability accordingly. The phosphoryl (-PO3) grafted branch is employed in the functional polymer to facilitate attaching to the HA substrate. In addition, the polymer integrates the nonfouling polymer brushes of poly(ethylene glycol) (PEG) with the cell-adhesive moiety of cyclic Arg-Gly-Asp-d-Phe-Cys peptides (cRGD). A systematic study on the as-synthesized PEGylated graft copolymer indicates a synergistic binding mechanism of the NH2 and PO3 groups to HA, achieving a high surface coverage with desirable adsorption stability. The cRGD/PEGylated copolymers of optimized grafting architecture are proven to effectively adsorb to HA surfaces as a self-assembled copolymer monolayer, showing stability with minimal desorption even in a complex, physiological medium and effectively preventing nonspecific protein adsorption as examined with X-ray photoelectron spectroscopy (XPS) and a quartz crystal microbalance with dissipation (QCM-D). Direct adhesion assays further confirm that the enhanced coating stability and biofunction durability of the phosphonate-grafted, cRGD-PEGylated copolymer can considerably promote osteoblast attachment on HA surfaces, meanwhile preventing microbial adhesion. This research has resulted in a solution of self-assembly polymer structure optimization that exhibits stable nonfouling characteristics.

The fabrication of the chitosan-based bioink for in vitro tissue repair and regeneration: A review

The repair and regeneration of the injured tissues or organs is a major challenge for biomedicine, and the emerging 3D bioprinting technology as a class of promising techniques in biomedical research for the development of tissue engineering and regenerative medicine. Chitosan-based bioinks, as the natural biomaterials, are considered as ideal materials for 3D bioprinting to design and fabricate the various scaffold due to their unique dynamic reversibility and fantastic biological properties. Our review aims to provide an overview of chitosan-based bioinks for in vitro tissue repair and regeneration, starting from modification of chitosan that affect these bioprinting processes. In addition, we summarize the advances in chitosan-based bioinks used in the various 3D printing strategies. Moreover, the biomedical applications of chitosan-based bioinks are discussed, primarily centered on regenerative medicine and tissue modeling engineering. Finally, current challenges and future opportunities in this field are discussed. The combination of chitosan-based bioinks and 3D bioprinting will hold promise for developing novel biomedical scaffolds for tissue or organ repair and regeneration.

Nano-/micro-scaled hydroxyapatite ceramic construction and the regulation of immune-associated osteogenic differentiation

Hydroxyapatite (HA) bioceramic is a promising substitute for bone defects, and the surface properties are major factors that influence bioactivity and osteoinductivity. In this study, two kinds of HA bioceramics with nanoscale (n-HA) and microscale (m-HA) surface topography were designed to mimic the natural bone, thus enhancing the stimulation of osteogenic differentiation and revealing the potential mechanism. Compared to m-HA, n-HA owned a larger surface roughness, a stronger wettability, and reduced hardness and indentation modulus. Based on these properties, n-HA could maintain the conformation of vitronectin better than m-HA, which may contribute to higher cellular activities and a stronger promotion of osteogenic differentiation of mesenchymal stem cells (MSCs). Further RNA sequencing analysis compared the molecular expression between n-HA and m-HA. Six hundred twenty-seven differentially expressed genes were identified in MSCs, and 17 upregulated genes and 610 downregulated genes were included when n-HA compared to m-HA. The GO cluster analysis and enriched Kyoto encyclopedia of genes and genome signaling pathways revealed a close correlation with the immune process in both upregulated (chemokine signaling pathway and cytokine-cytokine receptor interaction) and downregulated pathways (osteoclasts differentiation). It suggested that the nanoscale surface topography of HA enhanced the osteoinductivity of MSCs and could not be separated from its regulation of immune function and the retention of adsorbed protein conformation.