Impacts of pre-treatment methods on the morphology, crystal structure, and defects formation of hydroxyapatite extracted from Nile tilapia scales

The comprehensive control of hydroxyapatite (HAp), involving morphological and structural variations, particle sizes, and defect formations, has garnered considerable attention for its versatile functionalities, rendering it applicable in diverse contexts. This work examined the shape, structure and optical characteristics, and defect formation in hydroxyapatite (HAp) extracted from Nile tilapia (Oreochromis niloticus) scales with various pre-treatments through experiments and density functional theory (DFT) calculations. Utilizing scanning electron microscopy, our findings revealed that dried fish scales (FS-D) exhibited a layered pattern of collagen fibers, while boiled fish scales (FS-B) had smoother surfaces and significantly reduced collagen content. After calcination, the FS-D sample produced nanorods with an average length of 150 ± 44 nm, whereas the FS-B samples yielded agglomerated spherical particles whose size increased with the rising calcining temperature. In-depth analysis through X-ray diffraction and Fourier-transform infrared spectroscopy confirmed the presence of biphasic calcium phosphates in the FS-B samples, while the FS-D sample presented a pure HAp phase. The boiled fish scale calcined at 800 °C (FS-B800) exhibited an optical band gap (Eg) of 5.50 eV, whereas the dried fish scale calcined at 800 °C (FS-D800) showed two Eg values of 2.87 and 3.97 eV, as determined by UV-visible spectroscopy. DFT calculations revealed that the band gap of 3.97 eV correlated with OH- vacancies, while that of 2.87 eV indicated Mn-substituted HAp, explaining the blue powder. The Eg value for the white powder resembled pure HAp, S- and Cl- substituted OH- vacancies, and various cations substituting Ca sites of HAp. Different pre-treatment procedures influence the characteristics of HAp, offering opportunities for applications in bone replacement and scaffolds for bone tissue engineering.

Balance between the CMC/ACP Nanocomplex and Blood Assimilation Orchestrates Immunomodulation of the Biomineralized Collagen Matrix

Calcium phosphate-based biomineralized biomaterials have broad application prospects. However, the immune response and foreign body reactions elicited by biomineralized materials have drawn substantial attention recently, contrary to the immune microenvironment optimization concept. Therefore, it is important to clarify the immunomodulation properties of biomineralized materials. Herein, we prepared the biomineralized collagen matrix (BCM) and screened the key immunomodulation factor carboxymethyl chitosan/amorphous calcium phosphate (CMC/ACP) nanocomplex. The immunomodulation effect of the BCM was investigated in vitro and in vivo. The BCM triggered evident inflammatory responses and cascade foreign body reactions by releasing the CMC/ACP nanocomplex, which activated the potential TLR4-MAPK/NF-κB pathway, compromising the collagen matrix biocompatibility. By contrast, blocking the CMC/ACP nanocomplex release via the blood assimilation process of the BCM mitigated the inflammation and foreign body reactions, enhancing biocompatibility. Hence, the immunomodulation of the BCM was orchestrated by the balance between the CMC/ACP nanocomplex and the blood assimilation process. Controlling the release of the CMC/ACP nanocomplex to accord the biological effects of ACP with the temporal regenerative demands is key to developing advanced biomineralized materials.

Incorporating the Antioxidant Fullerenol into Calcium Phosphate Bone Cements Increases Cellular Osteogenesis without Compromising Physical Cement Characteristics

Herein, fullerenol (Ful), a highly water-soluble derivative of C60 fullerene with demonstrated antioxidant activity, is incorporated into calcium phosphate cements (CPCs) to enhance their osteogenic ability. CPCs with added carboxymethyl cellulose/gelatin (CMC/Gel) are doped with biocompatible Ful particles at concentrations of 0.02, 0.04, and 0.1 wt v%-1 and evaluated for Ful-mediated mechanical performance, antioxidant activity, and in vitro cellular osteogenesis. CMC/gel cements with the highest Ful concentration decrease setting times due to increased hydrogen bonding from Ful's hydroxyl groups. In vitro studies of reactive oxygen species (ROS) scavenging with CMC/gel cements demonstrate potent antioxidant activity with Ful incorporation and cement scavenging capacity is highest for 0.02 and 0.04 wt v%-1 Ful. In vitro cytotoxicity studies reveal that 0.02 and 0.04 wt v%-1 Ful cements also protect cellular viability. Finally, increase of alkaline phosphatase (ALP) activity and expression of runt-related transcription factor 2 (Runx2) in MC3T3-E1 pre-osteoblast cells treated with low-dose Ful cements demonstrate Ful-mediated osteogenic differentiation. These results strongly indicate that the osteogenic abilities of Ful-loaded cements are correlated with their antioxidant activity levels. Overall, this study demonstrates exciting potential of Fullerenol as an antioxidant and proosteogenic additive for improving the performance of calcium phosphate cements in bone reconstruction procedures.

Hydroxyapatite-based carriers for tumor targeting therapy

At present, targeted drug delivery is regarded as the most effective means of tumor treatment, overcoming the lack of conventional chemotherapeutics that are difficult to reach or enter into cancer cells. Hydroxyapatite (HAP) is the main component of biological hard tissue, which can be regarded as a suitable drug carrier due to its biocompatibility, nontoxicity, biodegradation, and absorbability. This review focuses on the cutting edge of HAP as a drug carrier in targeted drug delivery systems. HAP-based carriers can be obtained by doping, modification, and combination, which benefit to improve the loading efficiency of drugs and the response sensitivity of the microenvironment in the synthesis process. The drug adsorbed or in situ loaded on HAP-based carriers can achieve targeted drug delivery and precise treatment through the guidance of the in vivo microenvironment and the stimulation of the in vitro response. In addition, HAP-based drug carriers can improve the cellular uptake rate of drugs to achieve a higher treatment effect. These advantages revealed the promising potential of HAP-based carriers from the perspective of targeted drug delivery for tumor treatment.

Synthesis and application of nanometer hydroxyapatite in biomedicine

Nano-hydroxyapatite (nano-HA) has been widely studied as a promising biomaterial because of its potential mechanical and biological properties. In this article, different synthesis methods for nano-HA were summarized. Key factors for the synthesis of nano-HA, including reactant concentration, effects of temperature, PH, additives, aging time, and sintering, were separately investigated. The biological performances of the nano-HA depend strongly on its structures, morphology, and crystallite sizes. Nano-HA with different morphologies may cause different biological effects, such as protein adsorption, cell viability and proliferation, angiogenesis, and vascularization. Recent research progress with respect to the biological functions of the nano-HA in some specific biological applications are summarized and the future development of nano-sized hydroxyapatite is prospected.

Advanced Fusion Strategies for the Production of Functionalized Potato Virus X Virions

Plant virions are ideal for nanotechnology applications because they are structurally diverse and can self-assemble naturally, allowing for large-scale production in plants by molecular farming. Potato virus X (PVX) is particularly amenable due to the unique properties of its filamentous and flexible capsid, but efficient strategies are required to adapt the surface properties of PVX, such as the attachment of proteins and peptides. This chapter describes the selection and utilization of 2A ribosomal skip sequences, allowing the presentation of heterologous proteins and peptides as N-terminal fusions to the PVX coat protein at different densities. Another strategy for the rapid modification of PVX capsids is the plug-and-display module of the SpyTag/SpyCatcher system. The SpyTag can be presented on the PVX surface, allowing for the attachment of any protein fused to the SpyCatcher sequence.

Carbon Nanomaterials Modified Biomimetic Dental Implants for Diabetic Patients

Dental implants are used broadly in dental clinics as the most natural-looking restoration option for replacing missing or highly diseased teeth. However, dental implant failure is a crucial issue for diabetic patients in need of dentition restoration, particularly when a lack of osseointegration and immunoregulatory incompetency occur during the healing phase, resulting in infection and fibrous encapsulation. Bio-inspired or biomimetic materials, which can mimic the characteristics of natural elements, are being investigated for use in the implant industry. This review discusses different biomimetic dental implants in terms of structural changes that enable antibacterial properties, drug delivery, immunomodulation, and osseointegration. We subsequently summarize the modification of dental implants for diabetes patients utilizing carbon nanomaterials, which have been recently found to improve the characteristics of biomimetic dental implants, including through antibacterial and anti-inflammatory capabilities, and by offering drug delivery properties that are essential for the success of dental implants.

Radiation-Induced Stable Radicals in Calcium Phosphates: Results of Multifrequency EPR, EDNMR, ESEEM, and ENDOR Studies

This article presents the results of a study of radiation-induced defects in various synthetic calcium phosphate (CP) powder materials (hydroxyapatite—HA and octacalcium phosphate—OCP) by electron paramagnetic resonance (EPR) spectroscopy at the X, Q, and W-bands (9, 34, 95 GHz for the microwave frequencies, respectively). Currently, CP materials are widely used in orthopedics and dentistry owing to their high biocompatibility and physico-chemical similarity with human hard tissue. It is shown that in addition to the classical EPR techniques, other experimental approaches such as ELDOR-detected NMR (EDNMR), electron spin echo envelope modulation (ESEEM), and electron-nuclear double resonance (ENDOR) can be used to analyze the electron–nuclear interactions of CP powders. We demonstrated that the value and angular dependence of the quadrupole interaction for 14N nuclei of a nitrate radical can be determined by the EDNMR method at room temperature. The ESEEM technique has allowed for a rapid analysis of the nuclear environment and estimation of the structural positions of radiation-induced centers in various crystal matrices. ENDOR spectra can provide information about the distribution of the nitrate radicals in the OCP structure.

Consecutive dephosphorylation by alkaline phosphatase-directed in situ formation of porous hydrogels of SF with nanocrystalline calcium phosphate ceramics for bone regeneration

Alkaline phosphatase, as an enzyme involved in the process of bone mineralization and regeneration, was incorporated into a solution of SF to induce its gelation and mineralization through consecutive dephosphorylation actions on different substrates. In these processes, alkaline phosphatase firstly worked on a small peptide of NapGFFYp by removing its hydrophilic phosphate group. The resulted NapGFFY performed supramolecular assembly in the solution of SF and synergistically induced the conformation transition of SF from random coil to β-sheet structures, leading to the formation of a stable SF hydrogel under physiological conditions. And then, the entrapped ALP within the SF-NY gel network retained its catalytic activity, released phosphate ions from glycerophosphate, and catalysed the formation of calcium phosphate minerals within the porous gel. Because of the mild conditions of these processes and good biocompatibility of the scaffold, the mineralized SF gel can work as a biomimetic scaffold to promote the osteogenic differentiation of rBMSCs and stimulate femoral defect regeneration in a rat model.

Design of hydroxyapatite bioceramics with micro-/nano-topographies to regulate the osteogenic activities of bone morphogenetic protein-2 and bone marrow stromal cells

Biomimicking the nanostructure of natural bone apatite to enhance the bioactivity of hydroxyapatite (HA) biomaterials is an eternal topic in the bone regeneration field. In the present study, we designed four kinds of HA bioceramics with micro- to nanosized grains and investigated the effects of bioceramic topographies on the structures of bone morphogenetic protein-2 (BMP-2) and the effects on the responses of bone marrow stromal cells (BMSCs). Compared to the samples with submicron-scale crystalline particles, HA bioceramics with grain sizes of 104.6 ± 27.8 nm exhibited increased roughness, improved hydrophilicity and enhanced mechanical properties. The synergistic effects of these surface characteristics could well maintain the conformation of BMP-2, facilitate cell adhesion and spreading, and activate the osteogenic differentiation of BMSCs. Furthermore, SBF immersion and in vivo canine intramuscular implantation confirmed that the HA bioceramics with nanotopography also processed excellent bone-like apatite forming ability and outstanding osteoinductivity. In summary, these findings suggest that the nanotopography of HA bioceramics is a critical factor to enhance their bioactivity and osteoinductivity.

Surface mineralized biphasic calcium phosphate ceramics loaded with urine-derived stem cells are effective in bone regeneration

BACKGROUND

Segmental bone defects caused by trauma, tumors, or infection are a serious challenge for orthopedists in the world. Recent developments in tissue engineering have provided a new treatment for segmental bone defects. Urine-derived stem cells (USCs) can be obtained noninvasively and might be a new kind of seed cells used in bone tissue regeneration. Therefore, the first aim of the present study was to investigate the biological characteristics of USCs. The second aim of the present study was to study the osteogenic effect of surface mineralized biphasic calcium phosphate ceramics (BCPs) loaded with USCs in vitro and in vivo.

METHODS

We isolated USCs from the urine of healthy adult donors and evaluated the biological characteristics of USCs in vitro. We mineralized the surface of BCPs by simulated body fluid (SBF). Cell adhesion and proliferation of USCs on the surface mineralized BCPs were evaluated. Osteogenic proteins and genes of USCs on the surface mineralized BCPs were texted by enzyme-linked immunosorbent assay (ELISA) and real-time polymerase chain reaction (RT-PCR) assay. Critical-sized segmental bone defects model in New Zealand white rabbits were established and randomly divided into 4 groups (surface mineralized BCPs loaded with USCs, BCPs loaded with USCs, surface mineralized BCPs, and BCPs) based on the implant they received. The therapeutic efficacy of the scaffolds in a large bone defect at post-implantation was evaluated by imaging and histological examination.

RESULTS

USCs isolated in our study expressed stem cell-specific phenotypes and had a stable proliferative capacity and multipotential differentiation capability. Surface mineralized BCPs promoted osteogenic proteins and genes expression of USCs without affecting the proliferation of USCs. After 10 weeks, the amount of new bone formation was the highest in the group of surface mineralized BCPs loaded with USCs.

CONCLUSION

USCs, from non-invasive sources, have good application prospects in the field of bone tissue engineering. Surface mineralized BCPs can significantly enhance osteogenic potential of USCs without changing biological characteristics of BCPs. Surface mineralized BCPs loaded with USCs are effective in repairing of critical-sized segmental bone defects in rabbits.

In Vitro Uptake of Hydroxyapatite Nanoparticles and Their Effect on Osteogenic Differentiation of Human Mesenchymal Stem Cells

There have been many applications in biomedical fields based on hydroxyapatite nanoparticles (HA NPs) over the past decades. However, the biocompatibility of HANPs is affected by exposure dose, particle size, and the way of contact with cells. The objective of this study is to investigate the effect of HA NPs with different sizes on osteogenesis using human mesenchymal stem cells (hMSCs). Three different-sized HA NPs (~50, ~100, and ~150 nm, resp.) were synthesized to study the cytotoxicity, cellular uptake, and effect on osteogenic differentiation of hMSCs. The results clearly showed that each size of HA NPs had dose-dependent cytotoxicity on hMSCs. It was found that HA NPs could be uptaken into hMSCs. The osteogenic differentiation of hMSCs was evaluated through alkaline phosphatase (ALP) activity measurement, ALP staining, immunofluorescent staining for osteopontin (OPN), and real-time polymerase chain reaction (RT-PCR) examination. As expected, HA NPs of all sizes could promote the differentiation of hMSCs towards osteoblast lineage. Among the three sizes, smaller-sized HA NPs (~50 and ~100 nm) appeared to be more effective in stimulating osteogenic differentiation of hMSCs.

Optimized Bone Regeneration in Calvarial Bone Defect Based on Biodegradation-Tailoring Dual-shell Biphasic Bioactive Ceramic Microspheres

Bioceramic particulates capable of filling bone defects have gained considerable interest over the last decade. Herein, dual-shell bioceramic microspheres (CaP@CaSi@CaP, CaSi@CaP@CaSi) with adjustable beta-tricalcium phosphate (CaP) and beta-calcium silicate (CaSi) distribution were fabricated using a co-concentric capillary system enabling bone repair via a tailorable biodegradation process. The in vitro results showed the optimal concentration (1/16 of 200 mg/ml) of extracts of dual-shell microspheres could promote bone marrow mesenchymal cell (BMSC) proliferation and enhance the level of ALP activity and Alizarin Red staining. The in vivo bone repair and microsphere biodegradation in calvarial bone defects were compared using micro-computed tomography and histological evaluations. The results indicated the pure CaP microspheres were minimally resorbed at 18 weeks post-operatively and new bone tissue was limited; however, the dual-shell microspheres were appreciably biodegraded with time in accordance with the priority from CaSi to CaP in specific layers. The CaSi@CaP@CaSi group showed a significantly higher ability to promote bone regeneration than the CaP@CaSi@CaP group. This study indicates that the biphasic microspheres with adjustable composition distribution are promising for tailoring material degradation and bone regeneration rate, and such versatile design strategy is thought to fabricate various advanced biomaterials with tailorable biological performances for bone reconstruction.

Multifunctional HA/Cu nano-coatings on titanium using PPy coordination and doping via pulse electrochemical polymerization

An anti-wear and antibacterial hydroxyapatite nanoparticle bioactive coating on a titanium matrix is fabricated through hydroxyapatite/copper nanoparticle co-deposition.

Bone grafts and biomaterials substitutes for bone defect repair: A review

Bone grafts have been predominated used to treat bone defects, delayed union or non-union, and spinal fusion in orthopaedic clinically for a period of time, despite the emergency of synthetic bone graft substitutes. Nevertheless, the integration of allogeneic grafts and synthetic substitutes with host bone was found jeopardized in long-term follow-up studies. Hence, the enhancement of osteointegration of these grafts and substitutes with host bone is considerably important. To address this problem, addition of various growth factors, such as bone morphogenetic proteins (BMPs), parathyroid hormone (PTH) and platelet rich plasma (PRP), into structural allografts and synthetic substitutes have been considered. Although clinical applications of these factors have exhibited good bone formation, their further application was limited due to high cost and potential adverse side effects. Alternatively, bioinorganic ions such as magnesium, strontium and zinc are considered as alternative of osteogenic biological factors. Hence, this paper aims to review the currently available bone grafts and bone substitutes as well as the biological and bio-inorganic factors for the treatments of bone defect.

Functional calcium phosphate composites in nanomedicine

Calcium phosphate (CaP) materials have many peculiar and intriguing properties. In nature, CaP is found in nanostructured form embedded in a soft proteic matrix as the main mineral component of bones and teeth. The extraordinary stoichiometric flexibility, the different stabilities exhibited by its different forms as a function of pH and the highly dynamic nature of its surface ions, render CaP one of the most versatile materials for nanomedicine. This review summarizes some of the guidelines so far emerged for the synthesis of CaP composites in aqueous media that endow the material with tailored crystallinity, morphology, size, and functional properties. First, we introduce very briefly the areas of application of CaP within the nanomedicine field. Then through some selected examples, we review some synthetic routes where the presence of functional units (small templating molecules like surfactants, or oligomers and polymers) assists the synthesis and at the same time impart the functionality or the responsiveness desired for the end-application of the material. Finally, we illustrate two examples from our laboratory, where CaP is decorated by biologically active polymers or prepared within a thermo- and magneto-responsive hydrogel, respectively.

Critical review: Injectability of calcium phosphate pastes and cements

Calcium phosphate cements (CPC) have seen clinical success in many dental and orthopaedic applications in recent years. The properties of CPC essential for clinical success are reviewed in this article, which includes properties of the set cement (e.g. bioresorbability, biocompatibility, porosity and mechanical properties) and unset cement (e.g. setting time, cohesion, flow properties and ease of delivery to the surgical site). Emphasis is on the delivery of calcium phosphate (CaP) pastes and CPC, in particular the occurrence of separation of the liquid and solid components of the pastes and cements during injection; and established methods to reduce this phase separation. In addition a review of phase separation mechanisms observed during the extrusion of other biphasic paste systems and the theoretical models used to describe these mechanisms are discussed.

STATEMENT OF SIGNIFICANCE

Occurrence of phase separation of calcium phosphate pastes and cements during injection limits their full exploitation as a bone substitute in minimally invasive surgical applications. Due to lack of theoretical understanding of the phase separation mechanism(s), optimisation of an injectable CPC that satisfies clinical requirements has proven difficult. However, phase separation of pastes during delivery has been the focus across several research fields. Therefore in addition to a review of methods to reduce phase separation of CPC and the associated constraints, a review of phase separation mechanisms observed during extrusion of other pastes and the theoretical models used to describe these mechanisms is presented. It is anticipated this review will benefit future attempts to develop injectable calcium phosphate based systems.

Preparation and biocompatibility of electrospinning PDLLA/β-TCP/collagen for peripheral nerve regeneration

A unique nerve conduit composed of poly(d,l-lactic acid) (PDLLA), β-tricalcium phosphate (β-TCP) and collagen was prepared by electrospinning for the first time.

Preparation and biological effects of apatite nanosheet-constructed porous ceramics

A kind of apatite nanosheet-constructed porous ceramics could mediate the osteogenic differentiation of mesenchymal stem cells.

Functional hydroxyapatite bioceramics with excellent osteoconductivity and stern-interface induced antibacterial ability

Osteogenic Ag/HAp bioceramics possess significant bacteria-killing abilities under ultra-low Ag⁺concentrations and the stern-interface induced antibacterial mechanism was explicitly proposed.

Preparation of pH-responsive mesoporous hydroxyapatite nanoparticles for intracellular controlled release of an anticancer drug

A well-defined core–shell nano-carrier (PAA–MHAPNs) was successfully synthesized based on a graft-onto method by using mesoporous hydroxyapatite nanoparticles (MHAPNs) as the core and polyacrylic acid (PAA) as the shell.

Continuous expansion of the interplanar spacing of octacalcium phosphate by incorporation of dicarboxylate ions with a side chain

We investigate the (100) interplanar spacing expansion behavior of octacalcium phosphate (OCP), revealing that OCP shows continuous and non-continuous interplanar spacing expansion upon incorporation of mercaptosuccinate and succinate ions, respectively.

Advances in synthesis of calcium phosphate crystals with controlled size and shape

Calcium phosphate (CaP) materials have a wide range of applications, including biomaterials, adsorbents, chemical engineering materials, catalysts and catalyst supports and mechanical reinforcements. The size and shape of CaP crystals and aggregates play critical roles in their applications. The main inorganic building blocks of human bones and teeth are nanocrystalline CaPs; recently, much progress has been made in the application of CaP nanocrystals and their composites for clinical repair of damaged bone and tooth. For example, CaPs with special micro- and nanostructures can better imitate the biomimetic features of human bone and tooth, and this offers significantly enhanced biological performances. Therefore, the design of CaP nano-/microcrystals, and the shape and hierarchical structures of CaPs, have great potential to revolutionize the field of hard tissue engineering, starting from bone/tooth repair and augmentation to controlled drug delivery devices. Previously, a number of reviews have reported the synthesis and properties of CaP materials, especially for hydroxyapatite (HAp). However, most of them mainly focused on the characterizations and physicochemical and biological properties of HAp particles. There are few reviews about the control of particle size and size distribution of CaPs, and in particular the control of nano-/microstructures on bulk CaP ceramic surfaces, which is a big challenge technically and may have great potential in tissue engineering applications. This review summarizes the current state of the art for the synthesis of CaP crystals with controlled sizes from the nano- to the macroscale, and the diverse shapes including the zero-dimensional shapes of particles and spheres, the one-dimensional shapes of rods, fibers, wires and whiskers, the two-dimensional shapes of sheets, disks, plates, belts, ribbons and flakes and the three-dimensional (3-D) shapes of porous, hollow, and biomimetic structures similar to biological bone and tooth. In addition, this review will also summarize studies on the controlled formation of nano-/microstructures on the surface of bulk ceramics, and the preparation of macroscopical bone grafts with 3-D architecture nano-/microstructured surfaces. Moreover, the possible directions of future research and development in this field, such as the detailed mechanisms behind the size and shape control in various strategies, the importance of theoretical simulation, self-assembly, biomineralization and sacrificial precursor strategies in the fabrication of biomimetic bone-like and enamel-like CaP materials are proposed.