The synthesis, characterization and in vivo study of mineral substituted hydroxyapatite for prospective bone tissue rejuvenation applications

Development of a bioactive tunable hyaluronic-protein bioconjugate hydrogel for tissue regenerative applications

Every year, there are approximately 500 000 peripheral nerve injury (PNI) procedures due to trauma in the US alone. Autologous and acellular nerve grafts are among current clinical repair options; however, they are limited largely by the high costs associated with donor nerve tissue harvesting and implant processing, respectively. Therefore, there is a clinical need for an off-the-shelf nerve graft that can recapitulate the native microenvironment of the nerve. In our previous work, we created a hydrogel scaffold that incorporates mechanical and biological cues that mimic the peripheral nerve microenvironment using chemically modified hyaluronic acid (HA). However, with our previous work, the degradation profile and cell adhesivity was not ideal for tissue regeneration, in particular, peripheral nerve regeneration. To improve our previous hydrogel, HA was conjugated with fibrinogen using Michael-addition to assist in cell adhesion and hydrogel degradability. The addition of the fibrinogen linker was found to contribute to faster scaffold degradation via active enzymatic breakdown, compared to HA alone. Additionally, cell count and metabolic activity was significantly higher on HA conjugated fibrinogen compared previous hydrogel formulations. This manuscript discusses the various techniques deployed to characterize our new modified HA fibrinogen chemistry physically, mechanically, and biologically. This work addresses the aforementioned concerns by incorporating controllable degradability and increased cell adhesivity while maintaining incorporation of hyaluronic acid, paving the pathway for use in a variety of applications as a multi-purpose tissue engineering platform.

The interaction between phenylboronic acid derivatives and active ingredients with diphenol structure of traditional Chinese medicine

Many active ingredients of traditional Chinese medicine with important pharmacological effects always have glycol or diphenol structure, which lays a foundation for the combination with phenylboronic acid (PBA) derivatives to form cyclic boronic esters compounds. Herein, four important pharmacological active ingredients, namely baicalein, baicalin, gallic acid and protocatechuic acid, were chosen to study the interaction with PBA derivatives. Five PBA derivatives of 3-aminophenylboronic acid monohydrate (APBA), 3-acrylaminophenylboronic acid (AAPBA), poly(3-acrylaminophenylboronic acid) (PAAPBA), poly([poly(ethylene glycol) methacrylate-block-3-acrylaminophenylboronic acid]) (PEbPB), and poly[poly(ethylene glycol) methacrylate-random-3-acrylaminophenylboronic acid] (PErPB) were used. The interactions between five PBA derivatives and four active ingredients were explored by fluorescent spectrophotometer using the alizarin red (ARS) method. The fluorescent intensity of PBA derivative-ARS-active ingredient mixture was decreasing with the increasing concentrations of active ingredients. In comparison, the fluorescent intensity of PAAPBA, PEbPB, and PErPB showed an obviously decrease after active ingredients were added, while the fluorescent intensity of APBA and AAPBA showed a gradually decrease after active ingredients were added. These results indicated a stronger interaction between PBA polymers and active ingredients than that of APBA and AAPBA. Simultaneously, PEbPB and PErPB could enhance cellular uptake of baicalin in A549 cells. This research provided new strategies for improving the bioavailability and water solubility, extending the circulation time, and wider application of the active ingredients of traditional Chinese medicine in the prevention and therapy of diseases.

New Horizons for Hydroxyapatite Supported by DXA Assessment-A Preliminary Study

Dual Energy X-ray Absorptiometry (DXA) is a tool that allows the assessment of bone density. It was first presented by Cameron and Sorenson in 1963 and was approved by the Food and Drug Administration. Misplacing the femoral neck box, placing a trochanteric line below the midland and improper placement of boundary lines are the most common errors made during a DXA diagnostic test made by auto analysis. Hydroxyapatite is the most important inorganic component of teeth and bone tissue. It is estimated to constitute up to 70% of human bone weight and up to 50% of its volume. Calcium phosphate comes in many forms; however, studies have shown that only tricalcium phosphate and hydroxyapatite have the characteristics that allow their use as bone-substituted materials. The purpose of this study is aimed at analyzing the results of hip densitometry and hydorxyapatite distribution in order to better assess the structure and mineral density of the femoral neck. However, a detailed analysis of the individual density curves shows some qualitative differences that may be important in assessing bone strength in the area under study. To draw more specific conclusions on the therapy applied for individual patients, we need to determine the correct orientation of the bone from the resulting density and document the trends in the density distribution change. The average results presented with the DXA method are insufficient.

The role of deep eutectic solvents and carrageenan in synthesizing biocompatible anisotropic metal nanoparticles

Plasmonic metal nanoparticles are widely used for many applications due to their unique optical and chemical properties. Over the past decade, anisotropic metal nanoparticles have been explored for imaging, sensing, and diagnostic applications. The variations and flexibility of tuning the size and shape of the metal nanoparticles at the nanoscale made them promising candidates for biomedical applications such as therapeutics, diagnostics, and drug delivery. However, safety and risk assessment of the nanomaterials for clinical purposes are yet to be made owing to their cytotoxicity. The toxicity concern is primarily due to the conventional synthesis route that involves surfactants as a structure-directing agent and as a capping agent for nanoparticles. Wet chemical methods employ toxic auxiliary chemicals. However, the approach yields monodispersed nanoparticles, an essential criterion for their intended application and a limitation of the green synthesis of nanoparticles using plant extracts. Several biocompatible counterparts such as polymers, lipids, and chitosan-based nanoparticles have been successfully used in the synthesis of safe nanomaterials, but there were issues regarding reproducibility and yield. Enzymatic degradation was one of the factors responsible for limiting the efficacy. Hence, it is necessary to develop a safer and nontoxic route towards synthesizing biocompatible nanomaterials while retaining morphology, high yield, and monodispersity. In this regard, deep eutectic solvents (DESs) and carrageenan as capping agent for nanoparticles can ensure the safety. Carrageenan has the potential to act as antibacterial and antiviral agent, and adds enhanced stability to the nanoparticles. This leads to a multidimensional approach for utilizing safe nanomaterials for advanced biomedical and clinical applications.

Lanthanides-Substituted Hydroxyapatite/Aloe vera Composite Coated Titanium Plate for Bone Tissue Regeneration

PURPOSE

To develop the surface-treated metal implant with highly encouraged positive properties, including high anti-corrosiveness, bio-activeness and bio-compatibleness for orthopedic applications.

METHODS

In this work, the surface of commercially pure titanium (Ti) metal was treated with bio-compatible polydopamine (PD) by merely immersing the Ti plate in PD solution. The composite of trivalent lanthanide minerals (La3+, Ce3+ and Gd3+)-substituted hydroxyapatite (MHAP) with Aloe vera (AV) gel was prepared and coated on the PD-Ti plate by electrophoretic deposition (EPD) method. The choice of trivalent lanthanide ions is based on their bio-compatible nature and bone-seeking properties. The formation of the PD layer, composites, and composite coatings on Ti plate and PD-Ti surface was confirmed by FT-IR, XRD, SEM and HR-TEM observations. In-vitro assessments such as osteoblasts like MG-63 cell viability, alkaline phosphatase activity and mineralization ability of the MHAP/AV composite were tested, and the composite-coated plate was implanted into a rat bone defect model for in-vivo bone regeneration studies.

RESULTS

The coating ability of the MHAP/AV composite was highly preferred to PD-treated Ti plate than an untreated Ti plate due to the metal absorption ability of PD. This was confirmed by SEM analysis. The in-vitro and in-vivo studies show the better osteogenic ability of MHAP/AV composite at 14th day and 4th week of an experimental period, respectively.

CONCLUSION

The osteoblast ability of the fabricated device without producing any adverse effect in the rat model recommends that the fabricated device would serve as a better platform on the hard tissue regeneration for load-bearing applications of orthopedics.

In Vivo Assessment of a Hydroxyapatite/κ-Carrageenan-Maleic Anhydride-Casein/Doxorubicin Composite-Coated Titanium Bone Implant

Here, we focus on the fabrications of an osteosarcoma implant for bone repair via the development of a hydroxyapatite/κ-carrageenan-maleic anhydride/casein with doxorubicin (HAP/κ-CA-MA-CAS/DOX) composite-deposited titanium (Ti) plate. The HAP/κ-CA-MA-CAS/DOX material was coated on the Ti plate through the EPD method (electrophoretic deposition), applying direct current (DC) signals to deposit the composite on the surface of the Ti plate. The physicochemical and morphological possessions and biocompatibility in vitro of the prepared nanocomposite were examined to assess its prospective effectiveness for purposes of bone regeneration. Excellent biocompatibility and elevated osteoconductivity were confirmed using MG63 osteoblast-like cells. In vivo studies were performed at tibia sites in Wistar rats, and rapid bone regeneration was detected at four weeks in defective bone. Overall, the studies demonstrate that the HAP/κ-CA-MA-CAS/DOX composite enhances the biocompatible and cell-stimulating biointerface of Ti metallic implants. As such, HAP/κ-CA-MA-CAS/DOX implants are viable prospects for osteosarcoma-affected bone regeneration.

Nanosized hydroxyapatite and β-tricalcium phosphate composite: Physico-chemical, cytotoxicity, morphological properties and in vivo trial

The objective of this work was to characterize the properties of a synthetic biomaterial composite with nanoparticles size (Blue Bone). This biomaterial is a composite recommended for dental and orthopedic grafting surgery, for guided bone regeneration, including maxillary sinus lift, fresh alveolus filling, and treatment of furcation lesions. The nano biomaterials surface area is from 30% to 50% higher than those with micro dimensions. Another advantage is that the alloplastic biomaterial has homogeneous properties due to the complete manufacturing control. The analyzed biomaterial composite was characterized by XRD, cytochemistry, scanning electron microscopy, porosimetry and in vivo experiments (animals). The results showed that the analyzed biomaterial composite has 78.76% hydroxyapatite [Ca₅(PO₄)₃(OH)] with monoclinic structure, 21.03% β-tricalcium phosphate [β -Ca₃(PO₄)₂] with trigonal structure and 0.19% of CaO with cubic structure, nanoparticles with homogeneous shapes, and nanoporosity. The in vivo experiments showed that the composite has null cytotoxicity, and the site of insertion biomaterials has a high level of vascularization and bone formation. The conclusion is that the synthetic biomaterial with Blue Bone designation presents characteristics suitable for use in grafting surgery applications.

Enhancement of bone consolidation using high-frequency pulsed electromagnetic short-waves and titanium implants coated with biomimetic composite embedded into PLA matrix: in vivo evaluation

Purpose

Bone consolidation after severe trauma is the most challenging task in orthopedic surgery. This study aimed to develop biomimetic composite for coating Ti implants. Afterwards, these implants were tested in vivo to assess bone consolidation in the absence or the presence of high-frequency pulsed electromagnetic short-waves (HF-PESW).

Materials

Biomimetic coating was successfully developed using multi-substituted hydroxyapatite (ms-HAP) functionalized with collagen (ms-HAP/COL), embedded into poly-lactic acid (PLA) matrix (ms-HAP/COL@PLA), and subsequently covered with self-assembled COL layer (ms-HAP/COL@PLA/COL, named HAPc).

Methods

For in vivo evaluation, 32 Wistar albino rats were used in four groups: control group (CG) with Ti implant; PESW group with Ti implant+HF-PESW; HAPc group with Ti implant coated with HAPc; HAPc+PESW group with Ti implant coated with HAPc+HF-PESW. Left femoral diaphysis was fractured and fixed intramedullary. From the first post-operative day, PESW and HAPc+PESW groups underwent HF-PESW stimulation for 14 consecutive days. Biomimetic coating was characterized by XRD, HR-TEM, SEM, EDX and AFM.

Results

Osteogenic markers (ALP and osteocalcin) and micro-computed tomography (CT) analysis (especially bone volume/tissue volume ratio results) indicated at 2 weeks the following group order: HAPc+PESW>HAPc≈PESW (P>0.05) and HAPc+PESW>control (P<0.05), indicating the higher values in HAPc+PESW group compared to CG. The fracture-site bone strength showed, at 2 weeks, the highest average value in HAPc+PESW group. Moreover, histological analysis revealed the most abundant COL fibers assembled in dense bundles in HAPc-PESW group. At 8 weeks, micro-CT indicated higher values only in HAPc+PESW group vs CG (P<0.05), and histological results showed a complete-healed fracture in groups: HAPc+PESW, HAPc and PESW, but with more advanced bone remodeling in HAPc+PESW group.

Conclusion

Using Ti implants coated by HAPc jointly with HF-PESW stimulation positively influenced the bone consolidation process, especially in its early phase, thus potentially providing a superior strategy for clinical applications.

La-Doped biomimetic scaffolds facilitate bone remodelling by synchronizing osteointegration and phagocytic activity of macrophages

The capacity of osteoconduction held by HA/CS, osteoinduction by La³⁺, and biodegradability by a La-HA/CS composite, contributes to an ideal scaffold for osteointegration and remodelling.

Strontium-Doped Bioactive Glass Nanoparticles in Osteogenic Commitment

The present work has explored bioactive glass nanoparticles (BGNPs) and developed strontium-doped nanoparticles (BGNPsSr), envisioning orthopedic strategies compatible with vascularization. The nanoparticles were synthesized by the sol-gel method, achieving a diameter of 55 nm for BGNPs and 75 nm for BGNPsSr, and the inclusion of strontium caused no structural alteration. The nanoparticles exhibited high cytocompatibility for human umbilical vein endothelial cells (HUVECs) and SaOS-2. Additionally, the incorporation of strontium emphasized the tubule networking behavior of HUVECs. Our results demonstrate that the nanoparticle dissolution products encouraged the osteogenic differentiation of human adipose stem cells as it favored the expression of key genes and proteins associated with osteogenic lineage. This effect was markedly enhanced for BGNPsSr, which could prompt stem cell osteogenic differentiation without the typical osteogenic inducers. This study not only supports the hypothesis that BGNPs might play a significant role in osteogenic commitment but also highlights that the designed BGNPsSr is a valuable tool for stem cell "tune-up" in bone tissue engineering applications.