A novel nano-hydroxyapatite — PMMA hybrid scaffolds adopted by conjugated thermal induced phase separation (TIPS) and wet-chemical approach: Analysis of its mechanical and biological properties

Formulating Single Phasic Silicorhenanite (α- and β-Na2Ca4(PO4)2SiO4) Bioactive Glass Materials Competing with Commercial Crystalline Hydroxyapatite Bone Mineral for Biomedical Applications

Hydroxyapatite (HAP) is a well-known medically renowned bioactive material known for its excellent biocompatibility and mechanical stability, but it lacks fast bioactivity. The restricted release of ions from hydroxyapatite encourages the search for a faster bioactive material that could replicate other properties of HAP. A new sol-gel-mediated potentially bioactive glass material that could mimic the structure of HAP but can surpass the performance of HAP bioactively has been formulated in this study. Lefebvre et al. suggested that the silicorhenanite phase with the formula Na2Ca4(PO4)2SiO4 is isostructural to hydroxyapatite; however, data in support of this hypothesis are scant. This study succeeds in developing fast apatite-growth-inducing bioactive glass particles similar to the structure of hydroxyapatite. Also, for the first time, the existence and evolution of two forms of silicorhenanite (α- and β-Na2Ca4(PO4)2SiO4) have been unraveled, and their properties have been explored. The effect of calcination temperature on the phase formation of the biomaterial is notified by looking into the result that heat treatment to 900 °C resulted in α-Na2Ca4(PO4)2SiO4 (Sili 900) and 1000 °C yielded β-Na2Ca4(PO4)2SiO4 (Sili 1000). This study conveys a new finding that the hydroxyapatite is isostructural to β-Na2Ca4(PO4)2SiO4 but not to α-Na2Ca4(PO4)2SiO4. Raman spectroscopic analysis proved this structural similarity of Sili 1000 and c-HAP, with relative spectra possessing phosphate bands and the irrelevance of Sili 900 to Sili 1000 and c-HAP. The in vitro MTT assay using NIH 3T3 fibroblasts and in vivo wound healing study confirm the enhanced bioactivity and compatibility of Sili 900 and Sili 1000 compared to c-HAP, favored by the presence of a silica matrix and semicrystallinity. pH analysis proved the rapid ionic leaching out from Sili 900 and Sili 1000 and the faster reactivity of Sili 1000 with the fluid. This rapid burst of ions enhances the clotting ability of the Sili 1000 bioactive material and can be a good ibuprofen drug carrier, which is a potential challenger to hydroxyapatite.

Synergistic effects of silica-enriched bioactive glass and tri-calcium phosphate nanocomposites on BMP2 gene expression for bone repair and regeneration applications

This study focuses on the development of biomaterials for bone regeneration highlighting 59S bioactive glass (59S BG), tri-calcium phosphate (TCP), and their 1:1 composite (59S BG/TCP). The synthesized materials demonstrated excellent properties for bone tissue engineering. Characterization revealed their thermal stability up to 900 °C, as confirmed by thermogravimetric analysis (TGA), while X-ray diffraction (XRD) identified calcium phosphate and silicate phases. Functional groups and chemical bonding were elucidated using Fourier transform infrared spectroscopy (FTIR). The composite exhibited remarkable mechanical properties, with a hardness of 167.87 HV and a strength of 680.52 MPa, indicating its suitability for load-bearing applications. Biological evaluations confirmed promising performance, with in-vitro bioactivity showing apatite formation and reduced XRD peak intensity. Biocompatibility assessments revealed hemolysis below 5 % and a 300 % cell proliferation rate by day three ensuring minimal cytotoxicity and favorable blood compatibility. Protein adsorption studies demonstrated strong interactions with bovine serum albumin (BSA) and lysozyme, supporting protein stability. Additionally, the composite showed enhanced osteogenic potential with elevated BMP2 gene expression indicating its capacity to promote robust bone regeneration. The synergy between 59S BG and TCP underscores the composite's potential as a promising material for effective bone repair and regeneration.

Evaluation of acute and subacute dermal toxicity of antibacterial bioactive glass-infused surgical cotton gauze in Wistar rats

Mesoporous bioactive glass, with its versatile characteristics and morphology, holds significant potential as an ideal hemostatic material. However, limited data is available regarding its toxicity levels. Consequently, this research intends to assess the acute and repeated dose dermal toxicity of Mesoporous antibacterial bioactive glass microsphere impregnated nonwoven surgical cotton gauze (MABGmscg) dressing in albino Wistar rats, following the standards set by the Organization for Economic Cooperation and Development. In the acute dermal toxicity study, the impact of MABG (@2000mg/kg BW) mscg dressing was assessed following a single dermal application in both male and female Wistar rats (n = 10). Mortality, clinical signs, body weight fluctuations and gross observations were consistently monitored over a14 day period following the single dose. The results indicated that, MABG (@2000mg/kg BW) mscg dressing upon dermal exposure did not cause any adverse effect in acute dermal toxicity study in Wistar rats compared to control group. Given that 2000 mg/kg BW of MABG was deemed a nontoxic dose, a repeated dose dermal toxicity study of MABGmscg dressing was subsequently conducted at three dose levels (@200, 500, 1000 mg/kg BW) over 28 consecutive days in Wistar rats. During the study period, no unscheduled deaths occurred, and there were no clinical signs associated with treatment, body weight variations or abnormal gross findings at necropsy in any groups. The analysis concluded that, MABGmscg dressing is safe to be considered as a hemostatic dressing at the various tested dose levels in Wistar rats.

Advancing Bioactive Material for Mandibular Bone Regeneration: Transformation of Fibrous Mat into 3D Matrix Cotton for Enhanced Shape Retention and Rapid Hemostasis

Transformation of a fibrous mat into a three-dimensional (3D) scaffold opens up abundant innovative prospects in biomedical research, particularly for studying both soft as well as hard tissues. Electrospun nanofibers, which mimic the extracellular matrix have attracted significant attention in various studies. This research focuses on rapidly converting a fibrous mat made of polycaprolactone (PCL)/pluronic F-127 (PF-127) with different percentages of monetite calcium phosphate (MCP) into desirable 3D matrix cotton using a unique gas foaming technology. These matrix cottons possess biomimetic properties and have oriented porous structures. Using this innovative technique, various shapes of 3D matrix cotton, such as squares, hollow tubes, and other customizable forms, were successfully produced. Importantly, these 3D matrix cottons showed a consistent distribution of monetite particles with total porosity ranging from 90% to 98%. The structure of the 3D matrix cotton, its water/blood absorption capacity, the potential for causing non-hemolysis, and rapid hemostatic properties were thoroughly investigated. Additionally, periodontal cells were cultured on the 3D matrix cotton to assess their viability and morphology, revealing promising results. Furthermore, a coculture study involving NIH-3T3 and MG-63 cells on the 3D matrix cotton showed spheroidal formation within 24 h. Notably, in vitro assessments indicated that the matrix cotton containing 15% monetite (PCL-MMC15%) exhibited superior absorbent capabilities, excellent cell viability, and rapid hemostatic characteristics. Subsequently, the effectiveness of PCL-MMC15% in promoting mandibular bone regeneration was evaluated through an in vivo study on rabbits using a mandibular injury model. The results demonstrated that PCL-MMC15% facilitated the resolution of defects in the mandibular region by initiating new bone formation. Therefore, the presented 3D matrix cotton (PCL-MMC15%) shows significant promise for applications in both mandibular bone regeneration and hemostasis.

Crucial Chemical Revelations in 45S5 Bioactive Glass via Sequential Precursor Integration Order

Among the wet chemical nanoparticle fabrication techniques, the sol-gel process happens through hydrolysis and subsequent polycondensation reactions. The bioactive glass known as the 45S5 SiO2-Na2O-CaO-P2O5 quaternary system has intricate chemistry, yet its advantages benefit the biomedical field on an enormous scale. The order in which the ethanol and TEOS inclusions are exchanged was investigated in this work because it has a direct impact on the early hydrolysis process. Another strategy involves adding phosphate species to the sol before gelation, modifying the network chemistry, and interpreting the findings. Adding phosphate species before gelation in the biomaterial (E-Si-P) resulted in the formation of hydroxyapatite and other calcium silicate phases at 800 °C. Swapping ethanol and TEOS biomaterials (E-Si and Si-E) resulted in the sodium-calcium silicate phase only. Si-E with strong Si-O-Si siloxane rings demonstrated superior mechanical stability, hemocompatibility, and bioactivity. This compact Si-O-Si decreased the surface area of Si-E. XPS spectra revealed that E-Si-P has the lowest Na 1s binding energy (BE) and the highest BE for Si 2p. More Si-O-/Si-OH groups formed by E-Si make the network weak and decrease the surface area and protein adsorption. These differences significantly influenced the morphology, surface properties, mechanical studies, and compatibility test. This study has further unraveled the protocol to design a biomaterial with mechanical stability and load-bearing ability. In addition, the appropriate protocol to yield the desired property-rich biomaterial with preserved bioactivity, mechanical stability, cytocompatibility, as well and surface porosity has been elaborated in detail.

Multi-functional bandage - bioactive glass/metal oxides/alginate composites based regenerative membrane facilitating re-epithelialization in diabetic wounds with sustained drug delivery and anti-bactericidal efficacy

Chronic wounds, especially diabetic, foot and pressure ulcers are a major health problem affecting >10 % of the world's populace. Calcium phosphate materials, particularly, bioactive glasses (BG), used as a potential material for hard and soft tissue repair. This study combines nanostructured 45S5 BG with titania (TiO2) and alumina (Al2O3) into a composite via simple sol-gel method. Prepared composites with alginate (Alg) formed a bioactive nanocomposite hydrogel membrane via freezing method. X-ray diffraction revealed formation of two phases such as Na1.8Ca1.1Si6O14 and β-Na2Ca4(PO4)2SiO4 in the silica network. Fourier transformed InfraRed spectroscopy confirmed the network formation and cross-linking between composite and alginate. <2 % hemolysis, optimal in vitro degradation and porosity was systematically evaluated up to 7 days, resulting in increasing membrane bioactivity. Significant cytocompatibility, cell migration and proliferation and a 3-4-fold increase in Collagen (Col) and Vascular Endothelial Growth Factor (VEGF) expression were obtained. Sustained delivery of 80 % Dox in 24 h and effective growth reduction of S. aureus and destruction of biofilm development against E. coli and S. aureus within 24 h. Anatomical fin regeneration, rapid re-epithelialization and wound closure were achieved within 14 days in both zebrafish and in streptozotocin (STZ) induced rat in vivo animal models with optimal blood glucose levels. Hence, the fabricated bioactive membrane can act as effective wound dressing material, for diabetic chronic infectious wounds.

PMMA bone cement with L-arginine/nano fish bone nanocomplex for apatite formation

Bone cement is one of the materials used in orthopaedics that serves various functions, such as binding bone implants, replacing damaged bones and filling spaces within bones. Various materials have been used to synthesize bone cement, and one promising material for further research is fish bone waste-based bone cement. This study investigates the potential of fish bone waste-based bone cement by incorporating nano fish bone (NFB) and L-arginine (L-Arg) protein into polymethyl methacrylate (PMMA) to examine apatite growth. NFB derived from the Salmo salar fish positively influences osteoblast cell proliferation and differentiation, while L-Arg enhances biocompatibility and antibiotic properties. The NFB/L-Arg combination holds promise in accelerating new bone formation and cell growth, both of which are crucial for fracture healing and bone remodelling. Tensile strength tests reveal the superior performance of BC-PMMA-1-NFB/L-Arg (36.11 MPa) compared with commercial PMMA (32 MPa). Immersion tests with simulated body fluid (SBF) solution for 7 days reveal accelerated apatite layer formation, emphasizing the potential benefits of NFB/L-Arg in bone cement applications.

Rapidly derived equimolar Ca: P phasic bioactive glass infused flexible gelatin multi-functional scaffolds - A promising tissue engineering

The study aims to design and fabricate an ultra-easier multi-functional biomedical polymeric scaffold loaded with unique equimolar Ca:P phasic bioactive glass material (BG). Gelatin (G) - 45S5 bioactive glass (BG) scaffolds were synthesized via a simple laboratory refrigerator with higher biocompatibility and cytocompatibility. The results proved that BG has enhanced bio-mineralization of the scaffolds and results support that the G: BG (1:2) ratio is the more appropriate composition. Brunauer-Emmett-Teller (BET) study confirms the higher surface area for pure Gelatin and G: BG (1:2). Scanning Electron Microscopic images display the precipitation of hydroxycarbonate apatite layer over the scaffolds on immersing it in simulated body fluid. Alkaline phosphate activity proved that G: BG (1:2) scaffold could induce mitogenesis in MG-63 osteoblast cells, thus helping in hard tissue regeneration. Sirius red collagen deposition showed that higher content bioactive glass incorporated Gelatin polymeric scaffold G: BG (1:2) could induce rapid collagen secretion of NIH 3T3 fibroblast cell line that could help in soft tissue regeneration and earlier wound healing. The scaffolds were also tested for cell viability using NIH 3T3 fibroblast cell lines and MG 63 osteoblastic cell lines through methyl thiazolyl tetrazolium (MTT) assay. Thus, the study shows a scaffold of appropriate composition G: BG (1:2) can be a multifunctional material to regenerate hard and soft tissues.

Poly(methyl methacrylate) in Orthopedics: Strategies, Challenges, and Prospects in Bone Tissue Engineering

Poly(methyl methacrylate) (PMMA) is widely used in orthopedic applications, including bone cement in total joint replacement surgery, bone fillers, and bone substitutes due to its affordability, biocompatibility, and processability. However, the bone regeneration efficiency of PMMA is limited because of its lack of bioactivity, poor osseointegration, and non-degradability. The use of bone cement also has disadvantages such as methyl methacrylate (MMA) release and high exothermic temperature during the polymerization of PMMA, which can cause thermal necrosis. To address these problems, various strategies have been adopted, such as surface modification techniques and the incorporation of various bioactive agents and biopolymers into PMMA. In this review, the physicochemical properties and synthesis methods of PMMA are discussed, with a special focus on the utilization of various PMMA composites in bone tissue engineering. Additionally, the challenges involved in incorporating PMMA into regenerative medicine are discussed with suitable research findings with the intention of providing insightful advice to support its successful clinical applications.

Bilayer wound dressing composed of asymmetric polycaprolactone membrane and chitosan-carrageenan hydrogel incorporating storax balsam

A comprehensive approach is needed to develop multifunctional wound dressing that is simple yet efficient. In this work, Liquidambar orientalis Mill. storax loaded hydroxyethyl chitosan (HECS)-carrageenan (kC) based hydrogel (HECS-kC) and polydopamine coated asymmetric polycaprolactone membrane (PCL-DOP) were used to develop a multifunctional and modular bilayer wound dressing. Asymmetric PCL-DOP membrane was prepared by non-solvent induced phase separation (NIPS) followed by polydopamine coating and demonstrated an excellent barrier against bacteria while allowing permeability for 5.45 ppm dissolved‑oxygen and 2130 g/m2 water vapor transmission in 24 h in addition to 805 kPa tensile strength. Storax loaded HECS-kC hydrogel, on the other hand, demonstrated a pH-responsive degradation and swelling to provide necessary conditions to facilitate wound healing. The hydrogels showed stretchability above 140 %, mild adhesive strength on sheep skin and PCL-DOP membrane, while the storax incorporation enhanced antibacterial and antioxidant activity. Furthermore, rat full-thickness skin defect model showed that the developed bilayer wound dressing could significantly facilitate wound healing compared to Tegaderm™ and control groups. This study shows that the bilayered wound dressing has the potential to be used as a simple and effective wound care system.

Unveiling pro-angiogenesis and drug delivery using dual-bio polymer with bio-ceramic based nanocomposite hydrogels

In regenerative medicine, blood vessel development is of utmost importance as it enables the restoration of blood flow to tissues, and facilitate rapid vascularization in clinical tissue-engineered grafts. Herein, we fabricate the nanocomposite hydrogels from BG (clinophosinaite), alginate, Polyethylene glycol (PEG) and Dexamethasone (DEX) for the dual applications of drug delivery and angiogenesis assay. The hydrogels were fabricated through cross-linking approach and termed as alginate/PEG (A), alginate/PEG/clinophosinaite (AC), and alginate/PEG/clinophosinaite/DEX (ACD) that further subjected to structural characterization, using powder X-ray diffraction, and fourier-transform infrared spectroscopy. Porous nanostructures and sheets were imaged using field emission scanning electron microscopy (FESEM), which aid in nutrient and oxygen transport to support angiogenesis. The nanocomposite hydrogels evidently demonstrated good hemocompatibility and fully hydrophilic (30.20°). By means of liquid displacement technique, the nanocomposite hydrogel achieves 47% of porosity with the compressive strength about 0.04 MPa. In alginate/PEG/clinophosinaite and alginate/PEG/clinophosinaite/DEX systems, water absorption capacity reached 85% in 6 h and maintained 90% retention after 12 h. Further, leachable tests revealed that the hydrogel had not deformed even after 24 h. In vitro drug release studies evidently divulge sustainable delivery of DEX from alginate/PEG/clinophosinaite/DEX hydrogel with superior characteristics for drug release. The angiogenesis assay also evidently revealed that the AC and ACD hydrogels, demonstrated higher angiogenic properties with, promoted blood vessel development.

3D interconnected porous PMMA scaffold integrating with advanced nanostructured CaP-based biomaterials for rapid bone repair and regeneration

Bioactive scaffolds with polymer and nanostructured bioactive glass-based composites are promising materials for regenerative applications in consequence of close mimics of natural bone composition. Poly methyl methacrylate (PMMA) is a highly preferred thermoplastic polymer for orthopedic applications as it has good biocompatibility. Different kinds of bioactive, biodegradable as well as biocompatible biomaterial composites such as Bioglass (BG), Hydroxyapatite (Hap), and Tricalcium phosphate (TCP) can be integrated with PMMA, so as to augment the bioactivity, porosity as well as regeneration of hard tissues in human body. Among the bioactive glass, 60S BG (Bioactive glass with 60 percentage of Silica without Sodium ions) is better materials among aforementioned systems owning to mechanical stability as well as controlled bioactive material. In this work, the fabrication of PMMA-CaP (calcium phosphate)-based scaffolds were carried out by Thermal Induced Phase Separation method (TIPS). X-ray diffractogram analysis (XRD) is used to examine the physiochemical properties of the scaffolds that evidently reveal the presence of calcium phosphate besides calcium phosphate silicate phases. The Field Emission Scanning Electron Microscopy (FESEM) studies obviously exhibited the microstructure of the scaffolds as well as their interconnected porous morphology. The PMMA/60S BG/TCP (C50) scaffold has the maximum pore size, measuring 77 ± 23 μm, while the average pore size ranges from 50 ± 20 to 80 ± 23 μm. By performing a liquid displacement method, the C50 scaffold is found to have the largest porosity of 50%, high hydrophilicity of 118.16°, and a compression test reveals the scaffolds to have a maximum compressive strength of 0.16 MPa. The emergence of bone-like apatite on the scaffold surface after 1st and 21st days of SBF immersion is further supported by in vitro bioactivity studies. Cytocompatibility and hemocompatibility analyses undoubtedly confirmed the biocompatibility behavior of PMMA-based bioactive scaffolds. Nano-CT investigation demonstrates that PMMA-CaP scaffolds provide more or less alike morphologies of composites that resemble the natural bone. Therefore, this combination of scaffolds could be considered as potential biomaterials for bone regeneration application. This detailed study promisingly demonstrates the eminence of the unique scaffolds in the direction of regenerative medicines.

Research progress and future prospects of antimicrobial modified polyetheretherketone (PEEK) for the treatment of bone infections

Infection of the bone is a difficult problem in orthopedic diseases. The key and basis of the treatment of bone infection is the effective control of local infection, as well as the elimination of infection focus and dead cavities. The most commonly used approach utilized for the prevention and management of bone infection is the application of antibiotic bone cement. However, the incorporation of antibiotics into the cement matrix has been found to considerably compromise the mechanical characteristics of bone cement. Moreover, some investigations have indicated that the antibiotic release rate of antibiotic bone cement is relatively low. Polyetheretherketone (PEEK) and its composites have been considered to perfectly address the challenges above, according to its favorable biomechanical characteristics and diverse surface functionalizations. This article provides a comprehensive overview of the recent advancements in the antimicrobial modification of PEEK composites in the field of antibacterial therapy of bone infection. Furthermore, the potential application of PEEK-modified materials in clinical treatment was discussed and predicted.

Study on injectable silver-incorporated calcium phosphate composite with enhanced antibacterial and biomechanical properties for fighting bone cement-associated infections

Although commonly used in orthopedic surgery, bone cements often face a high risk of post-operative infection. Developing bone cement with antibacterial capability is an effective path for eliminating implant-associated infections. Herein, the potential of silver ions (Ag⁺) and silver nanoparticles (AgNPs) in modifying CPC for long-term antibacterial property was investigated. Ag⁺ ions or AgNPs of various concentrations were incorporated in starch-modified calcium phosphate bone cement (CPB) to obtain Ag⁺-containing (Ag⁺@CPB) and AgNPs-containing (AgNP@CPB) bone cements. The results showed that all silver-containing CPBs had setting times of about 25-40 min, compressive strengths of greater than 22 MPa, high cytocompatibility but inhibitory effect on Staphylococcus aureus growth. After soaking for 1 week, the mechanical properties and the cytocompatibility of all cements revealed no significant changes, but only CPB with a relatively high content of Ag⁺ (H-Ag⁺@CPB) maintained good antibacterial capability over the tested time period. In addition, all the cements showed high injectability and interdigitating capability in cancellous bone and demonstrated augmentation effect on the cannulated pedicle screws fixation in the Sawbones model. In summary, the sustainable antibacterial capability and enhanced biomechanical properties demonstrated that Ag⁺ ions were more suitable for the fabrication of antibacterial CPC compared to AgNPs. Also, the H-Ag⁺@CPB, with good injectability, high cytocompatibility, good interdigitating and biomechanical property in cancellous bone, and sustainable antibacterial effects, bears great potential for the treatments of bone infections or implant-associated infections.

Strength Evaluation of Functionalized MWCNT-Reinforced Polymer Nanocomposites Synthesized Using a 3D Mixing Approach

The incorporation of carboxyl functionalized multi-walled carbon nanotube (MWCNT- COOH) into a polymethyl methacrylate (PMMA) has been investigated. The resultant tensile and flexural mechanical properties have been determined. In this paper, a novel synthesis process for a MWCNT-reinforced polymer nanocomposite is proposed. The proposed method significantly eliminates the most challenging issues of the nano-dispersed phase, including agglomeration and non-homogeneous mixing within a given matrix material, and also resolves the issues occurring in conventional mixing processes. The results of scanning electron microscopy support these claims. This 3D-mixing process is followed by an extrusion process, using a twin-screw extruder for pristine MWCNT, and a compression molding process for COOH-MWCNT, to prepare test specimens for experimentally determining the mechanical properties. The test specimens are fabricated using 0.1, 0.5, and 1.0 wt.% MWCNT, with a remaining PMMA phase. The testing is conducted according to ASTM D3039 and ASTM D7264 standards. Significant improvements of 25.41%, 35.85%, and 31.75% in tensile properties and 18.27%, 48%, and 33.33% in flexural properties for 0.1, 0.5, and 1.0 wt.% COOH-MWCNT in PMMA, respectively, compared to non-functionalized MWCNTs, were demonstrated. The highest strength was recorded for the nanocomposite with 0.5 wt.% f-MWCNT content, indicating the best doping effect at a lower concentration of f-MWCNT. The proposed CNT-PMMA nanocomposite may be found suitable for use as a scaffold material in the domain of bone tissue engineering research. This type of research possesses a high strength requirement, which may be fulfilled using MWCNT. Furthermore, this analysis also shows a significant amount of enhancement in flexural strength, which is clinically required for fabricating denture bases.

Preparation and Biocompatibility of Poly Methyl Methacrylate (PMMA)-Mesoporous Bioactive Glass (MBG) Composite Scaffolds

In recent years, the rising number of bone diseases which affect millions of people worldwide has led to an increased demand for materials with restoring and augmentation properties that can be used in therapies for bone pathologies. In this work, PMMA- MBG composite scaffolds containing ceria (0, 1, 3 mol%) were obtained by the phase separation method. The obtained composite scaffolds were characterized by X-ray diffraction, infrared spectroscopy, and scanning electron microscopy. UV-Vis measurement and EDX analysis confirmed the presence of cerium ions in the composite scaffolds. Evaluation of the in-vitro biocompatibility using MTT assay showed that composite scaffold containing 1 mol% of ceria presented higher viability than control cells (100%) for concentrations ranging between 5 and 50% after 96 h of incubation.

3D-printed monolithic biofilters based on a polylactic acid (PLA) - hydroxyapatite (HAp) composite for heavy metal removal from an aqueous medium

High flux, monolithic water purification filters based on polylactic acid (PLA) functionalised with fish scale extracted hydroxyapatite (HAp) were prepared by solvent-assisted blending and thermally induced phase separation (TIPS), followed by twin-screw extrusion into filaments and processed via three-dimensional (3D) printing. The printed filters with consistent pore geometry and channel interconnectivity as well as homogenous distribution of HAp in the PLA matrix showed adsorption capabilities towards heavy metals i.e. cadmium (Cd) and lead (Pb) with maximum adsorption capacity of 112.1 mg g_HAp⁻¹ and 360.5 mg g_HAp⁻¹ for the metal salt of Pb and Cd, respectively. The adsorption was found to be driven by a combination of ion exchange, dissolution and precipitation on HAp and surface complexation.

Water purification filters based on polylactic acid functionalised with hydroxyapatite were prepared by solvent-assisted blending and thermally induced phase separation (TIPS), extruded into filaments and processed via three-dimensional (3D) printing.

Study of biomorphic calcium deficient hydroxyapatite fibres derived from a naturalHarakeke(Phormium tenax) leaf fibre template

The complex structure of natural bio-organic matter has inspired scientists to utilise these as templates to design 'biomorphic materials', which retain the intricate architecture of the materials while acting as a useful bioactive material. Biomorphic hydroxyapatite-based fibres were synthesised usingHarakekeleaf fibre as a template, which constitutes a powerful method for manufacturing bioactive ceramic fibres. Furthermore, in creating the hydroxyapatite-based fibres, a natural source of calcium and phosphate ions (from bovine bone) was utilised to create the digest solution in which the leaf fibres were immersed prior to their calcination to form the inorganic fibres. Chemical, thermogravimetric and microscopic characterisation confirmed that the final product was able to successfully replicate the shape of the fibres and furthermore be transformed into calcium deficient, bone-like hydroxyapatite.

Interplay between surface chemistry and osteogenic behaviour of sulphate substituted nano-hydroxyapatite

Surface potential and chemical compositions of the bioceramics are the core of therapeutic effect and are key factors to trigger the interfacial interactions with surrounding hard and soft tissues to repair and regeneration. Ionic substitution in hydroxyapatite (Hap) lattice significantly influences the zeta potential from -16.46 ± 0.66 mV to -6.01 ± 0.68 mV as well as an average nano-rod length from ~40 nm to ~26 nm with respect to SO₄^2- ion content. Moreover, the surface chemistry of Hap is mainly inter-related to SO₄^2- substitution rate at PO₄^2- site. Specifically, nano-sized feature with lowered negative surface potential influences the protein adsorption via their weak repulsive or attractive forces. Bovine serum albumin (BSA) and lysozyme (LSZ) adsorption studies confirmed the increased affinity to active binding sites of Hap's surface. Further, SO₄^2- ion substituted Hap (SNHA) showed improved in vitro biomineralization activity and alkaline phosphatase activity. Expression of osteogenic biomarkers such as collagen I, V, osteopontin and osteocalcin were evaluated in Saos-2 and MC3T3-E1 cells. Gene expression of these markers was influenced by SO₄^2- ion content in Hap (maximum with 10SNHA). Altogether, these data emphasizes that chemical composition and surface properties are dominant aspect in bioceramic development towards bone regeneration.

Biocidal activity of curcumin and cationic polymer possessing composites

There is a growing interest in new type of biocidal compounds with antibacterial properties against bacteria. In this study, new antibacterial synthetic materials bearing curcumin and cationic polymers were synthesized. In the synthesis stage, the methacrylate functional cationic monomer was synthesized via the Michael addition route by using 3-acryloxy-2-hydroxypropyl methacrylate and 3-amino pyridine to obtain Monomer 1. Monomer 1 was further quaternized with hexyl bromide to obtain a cationic methacrylate functional monomer. Free-radical polymerization of Monomer 1 and methyl acrylate was conducted in the presence of azobisisobutyronitrile under dimethylformamide solvent. The composite formulation was conducted by using turmeric extract Curcuma longa (curcumin), hydroxyapatite, montmorillonite, and silver nitrate. The materials were analyzed by using the methods of X-ray diffraction, nuclear magnetic resonance, Fourier transform infrared spectroscopy, and scanning electron microscopy. The biocidal activities against the bacteria Escherichia coli, Listeria monocytogenes, Salmonella, and Staphylococcus aureus were analyzed using agar well diffusion method. From the Fourier transform infrared, X-ray diffraction, and scanning electron microscopy analysis results of the synthesized nanocomposites, it is seen that they form strong connections with the components added to the composites and form an exfoliated structure. According to the antibacterial analysis results, the nanocomposites obtained have showed a strong antibacterial resistance against E.coli, L.monocytogenes, Salmonella, and S. aureus bacteria, and the high inhibition zone areas were obtained.

Micro- and Nanoparticulate Hydroxyapatite Powders as Fillers in Polyacrylate Bone Cement-A Comparative Study

Acrylate polymer-based bone cements constitute the most popular bonding agents used in regenerative surgery. Due to their inferior biocompatibility, however, these materials are often enriched with ceramic additives including hydroxyapatite (HAp). The aim of this paper was to perform a comparative study of the acrylate cements filled with different content (3–21%) of nano- and microscale hydroxyapatite. The work concerns a comparison of times and temperatures of the cross-linking reaction, as well as morphology, glass transition temperature, and principal mechanical properties of the resulting composites. Before being used as a filler, both HAp forms were subjected to an in-depth characterization of their morphology, specific surface area, pore size distribution, and wettability as well as chemical composition and structure. For that purpose, such analytical techniques as scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, tensiometry, Brunauer–Emmett–Teller surface area analysis, differential scanning calorimetry, Shore D hardness test, and Charpy impact test were used. The results indicated a drop of cross-linking temperature and an extension of setting time with the addition of µHAp. The µHAp-filled acrylate composites were characterized by a globular surface morphology, higher glass transition temperature, and lower hardness and impact strength compared to nHAp-filled materials. This relationship was evident at higher nHAp concentrations.

Biomechanical properties of 3D-printed bone models

Bone lesions resulting from large traumas or cancer resections can be successfully treated by directly using synthetic materials or in combination with tissue engineering methods (hybrid). Synthetic or hybrid materials combined with bone tissue's natural ability for regeneration and biological adaptation to the directions of loading, allow for full recovery of its biological functions. Increasing interest in new production methods or various types of regenerative membranes and shaped scaffolds means that methods such as additive manufacturing can significantly accelerate the preparation of constructs used in the further biological adaptation of natural tissue. The porosity that allows not only ingrowth of the natural tissue, but also the ability of the synthetic material to transfer loadings in the skeletal system during the regeneration interval, will have a significant impact on regenerative capacities. This work presents the results of preliminary analyzes of bone models in the field of mechanical strength for monotonically and cyclically loading conditions. The determined material constants, such as ultimate tensile strength, Young modulus, and toughness or fatigue life, can be used in numerical simulations of new membranes for the regeneration of damaged bone tissue.