Drug delivery and antimicrobial studies of chitosan-alginate based hydroxyapatite bioscaffolds formed by the Casein micelle assisted synthesis

The present study aims to develop a hydroxyapatite (HAP) based scaffold composite for orthopaedic applications and for that, we adopt a Casein (Cs) micelle assisted synthesis route for the formation of a composite. Following the synthesis and characterization of various fluorine (2% and 5%) substituted HAPs (FHAP), they have been tested for the release of Ciprofloxacin (CIP) drug and antimicrobial efficacy. The physicochemical characterization such as FTIR and Raman confirms the successful formation of the HAP composites. Similarly, the powder XRD and FESEM analysis have used for the confirmation of crystallinity and morphological behaviour, respectively. The elemental composition has confirmed using EDX analysis. The antimicrobial studies indicate that the 5% FHAP sample is possessing superior antifungal and antibacterial activities and the highest activity has been observed against the gram-positive bacteria (Staphylococcus aureus) with an inhibition zone of 47 mm while the gram-negative bacteria (Escherichia coli) has only 38 mm inhibition zone. The CIP drug release profile has been controlling with the Cs/5% FHAP sample. Therefore, this composite has carried out for the scaffold formation with the use of chitosan-alginate matrices. Further, characterization of chitosan-alginate/5% FHAP scaffold composite indicates porous, biodegradable, considerable water uptake and retention ability, along with the maintenance of controlled CIP drug-releasing properties. Based on the analysis, the as-synthesized chitosan-alginate/5% FHAP scaffold composite can be suitable for the biomedical and bioengineering applications of bone tissue growth and as an implant

Influence of sonication on the physicochemical and biological characteristics of selenium-substituted hydroxyapatites

Although the material hydroxyapatite (HAP) has excellent porous, biocompatible, and biodegradable properties, its mechanical strength and microbial inhibition rate are not adequate for its direct use in bone tissue engineering or in constructing artificial teeth. To overcome some of its limitations, in the present study, we have formed an organic-inorganic composite with an altered internal structureviadoping selenium (Se) cations into the lattice of HAP. We have synthesized Se-substituted HAP (Se-HAP) composites with different Se/P ratios (0.01, 0.05, and 0.1 M)viaa wet chemical route in which two different sets of samples were collected (1) after only precipitation (referred to as the precipitation method) and (2) after precipitation followed by sonication (referred to as the sonochemical method). FTIR and Raman spectroscopic analyses confirmed the successful doping of Se into the HAP matrices, while powder XRD studies indicated their highly crystalline nature, which was significantly influenced by Se doping. The XRD data also showed that the Se-HAP particles formed by the precipitation method have a size of 56 nm and those formed by the sonochemical method have a size of 29 nm. Morphological analysis by means of SEM and TEM indicated that the sonochemical method produces well-defined rod-shaped particles, while the precipitation method produces particles with agglomerated structures. Hemolytic studies confirmed that the Se-HAP particles are biocompatible, and that the hemolytic ratio increases with the Se content. In addition, antibacterial studies indicated that Se-HAP responds quite well against a Gram-positive strain (S. aureus), on a par with the response to a Gram-negative strain (P. aeruginosa). Finally,in vitrocell viability and proliferation studies indicated an increase in the proliferation capacity of non-cancer cells (NIH-3T3 fibroblasts) and a considerable reduction in the viability of cancer cells (MG-63 osteosarcoma). Based on the overall analysis, the Se-HAP samples formed by the sonochemical approach could have potential for biomedical applications in bone cell repair, growth, and regeneration

Improving the corrosion resistance and bioactivity of magnesium by a carbonate conversion-polycaprolactone duplex coating approach

Decreasing the rate of degradation of Mg has been the focus of developing various types of coatings for Mg. Though polycaprolactone (PCL) coating is capable of providing short-term improvement in corrosion resistance for Mg, the porous nature of the PCL coating and the inside out corrosion of Mg have led to cracking and delamination of the PCL coating. Poor adhesion of the PCL coating on Mg is another limitation. To overcome these limitations, the present study aims to explore magnesium carbonate coating as a pre-treatment. The study proposes a duplex coating approach, which involves deposition of magnesium carbonate by a chemical conversion method as the first layer over which a PCL coating is formed by the dip coating method. The morphological features, nature of functional groups, phase content, adhesive strength, etc., of the magnesium carbonate and duplex coating were evaluated by using scanning electron microscopy, FT-IR spectroscopy, X-ray diffraction measurement and tensile testing, respectively. The corrosion behaviour of the magnesium carbonate and duplex coating in Hanks' solution was evaluated by using potentiodynamic polarization, electrochemical impedance spectroscopy and immersion tests. The bioactivity of the magnesium carbonate and duplex coating was evaluated by immersing them in simulated body fluid. The extent of apatite growth served as a measure of their bioactivity. The study reveals that MgCO3 coating served as an excellent base for the deposition of the PCL layer and the duplex coating offered a good corrosion resistance in Hanks' solution and exhibited better bioactivity in simulated body fluid. The study concludes that the magnesium carbonate-PCL duplex coating is a viable approach to reduce the rate of corrosion of magnesium and to improve its bioactivity

Fabrication and characterization of porous scaffolds for bone replacements using gum tragacanth

The practice of bone implants is the standard procedure for the treatment of skeletal fissures, or to substitute and re-establish lost bone. A perfect scaffold ought to be made of biomaterials that duplicate the structure and properties of natural bone. However, the production of living tissue constructs that are architecturally, functionally and mechanically comparable to natural bone is the major challenge in the treatment and regeneration of bone tissue in orthopaedics and in dentistry. In this work, we have employed a polymeric replication method to fabricate hydroxyapatite (HAP) scaffolds using gum tragacanth (GT) as a natural binder. GT is a natural gum collected from the dried sap of several species of Middle Eastern legumes of the genus Astragalus, possessing antibacterial and wound healing properties. The synthesized porous HAP scaffolds were analyzed structurally and characterized for their phase purity and mechanical properties. The biocompatibility of the porous HAP scaffold was confirmed by seeding the scaffold with Vero cells, and its bioactivity assessed by immersing the scaffold in simulated body fluid (SBF). Our characterization data showed that the biocompatible porous HAP scaffolds were composed of highly interconnecting pores with compressive strength ranging from 0.036 MPa to 2.954 MPa, comparable to that of spongy bone. These can be prepared in a controlled manner by using an appropriate binder concentration and sintering temperature. These HAP scaffolds have properties consistent with normal bone and should be further developed for potential application in bone implants

Advanced lithium substituted hydroxyapatite nanoparticles for antimicrobial and hemolytic studies

In this study, pure hydroxyapatite (HAP) and lithium substituted hydroxyapatite (Li-HAP) nanoparticles were synthesized by a sonochemical synthesis process and investigated for their antimicrobial and hemolytic activities. The synthesized HAP and Li-HAP were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy. The XRD analysis confirmed the formation of the HAP phase both in the synthesized pure HAP and Li-HAP samples. It was also observed that the crystallite size was decreased in Li-HAP compared to pure HAP. FTIR analysis confirmed the presence of various functional groups (e.g. hydroxyl, phosphate etc. groups). Generally, hydroxyapatite has a rod and plate-like morphology. Upon doping, the rod and plate-like morphologies were modified to agglomerated needle-shaped HAP crystals. Antimicrobial, hemolytic and MTT studies were performed using human pathogens, human blood, and human bone cells, respectively, to investigate the biological activities of the synthesized HAP samples. The biological test results evidenced the biocompatibility and cytotoxicity of the HAP samples with better functionality of Li-HAP. This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique

Biosynthesised Silver Nanoparticles Loading onto Biphasic Calcium Phosphate for Antibacterial and Bone Tissue Engineering Applications

Biphasic calcium phosphate (BCP) serves as one of the substitutes for bone as it consists of an intimate mixture of beta-tricalcium phosphate (β-TCP) and hydroxyapatite (HAP) in different ratios. BCP, because of its inbuilt properties such as osteoconductivity, biocompatibility, and biostability in several clinical models serves as a bone substituent for orthopedic applications. Therefore, the present study aimed to assess the effectiveness of silver (Ag) nanoparticles (NPs) combined with BCP composites for the orthopedic sector of bone tissue regeneration and growth. In this regard, we first synthesized Ag-BCP microclusters by the double-emulsion method and then characterized the composite for various physicochemical properties, including the crystallinity and crystal structure, bonding and functionality, porosity, morphology, surface charges, topography, and thermal stability. In addition, the antibacterial activity of Ag-BCP was tested against gram-positive and gram-negative microorganisms such as Staphylococcus aureus, Candida albicans, and Escherichia coli. Finally, the cytocompatibility of Ag-BCP was confirmed against the fibroblast cells in vitro

A Facile Method to Modify the Characteristics and Corrosion Behavior of 304 Stainless Steel by Surface Nanostructuring toward Biomedical Applications

The study addresses how surface nanostructuring of AISI 304 stainless steel (SS) by surface mechanical attrition treatment (SMAT) influences its characteristic properties and corrosion behavior in Ringer’s solution. SMAT of 304 SS induced plastic deformation, enabled surface nanocrystallization, refined the grain size, transformed the austenite phase to strain induced α′-martensite phase, increased the surface roughness, induced defects/dislocations, imparted compressive residual stresses at the surface, decreased the contact angle, and increased surface energy. The change in properties of 304 SS following treatment using 5 and 8 mm ⌀ balls for 15, 30, 45, and 60 min has caused a deleterious influence on its corrosion resistance in Ringer’s solution, while an improvement in corrosion behavior is observed for those treated using 2 mm ⌀ balls. The increase in surface roughness, transformation of the austenite to α′-martensite phase, a higher extent of deformation, and the presence of larger number of defects/dislocations are main factors responsible for the lower corrosion resistance observed for 304 SS treated using 5 and 8 mm ⌀ balls in Ringer’s solution. In spite of having these attributes with a relatively lower extent, 304 SS treated using 2 mm ⌀ balls offered a better corrosion resistance and exhibits a better passivity. For those treated using 2 mm ⌀ balls, the ability of the nanocrystalline surface to promote passivation outweighs the deleterious influences caused by the limited amount of deformation and defects/dislocations. Based on the findings of this study, it is recommend that SMAT of 304 SS using 2 mm ⌀ balls for 15–30 min is the optimum condition to achieve the suitable surface profile, surface characteristics with better corrosion resistance

Nanoformulation of core-shell type hydroxyapatite-coated gum acacia towards the biomedical applications of enhanced bioactivity and controlled drug delivery

In this work, nanospherical hydroxyapatite (HAP) was prepared that has combined properties of controlled drug delivery, biocompatibility, and antibacterial activity to have applications in the biomedical sector. The composite was formed by the sintering of HAP in the presence of Gum acacia (GA) as an emulsifier (at 600 °C) and the composite's physical properties like nucleation, size, shape, crystallinity, and surface area were characterized using spectroscopic, electron microscopic and BET (Brunauer, Emmett and Teller) studies. Typical results of the FTIR study revealed the presence of characteristic phosphate and carbonate groups of HAP and XRD provided the mean crystallite size of GA-HAP in the range of 20–50 nm. The electron micrograph of GA-HAP showed nanorods with a smooth surface interspersed in GA with particle size <50 nm and a change of shape to spheres upon increasing the concentration of GA. The presence of C, O, Ca, and P confirmed through XPS was attributed to the major elemental composition of GA-HAP. Besides, BET studies indicated that the % of GA incorporated seemed to be greatly influenced by the porosity and surface area and this particular property determined the drug loading and leaching efficacy from the GA-HAP matrices when used for drug delivery applications. After bioactivity and leaching studies in the presence of SBF (simulated body fluid), we found that the increased concentration of GA (from 1% to 10%) caused a slowdown and sustained release/burst of the naringenin drug (43% over a 72 h period). Further, antibacterial studies using the clinical strains of bacteria proved that GA-HAP/N (drug-loaded GA-HAP) possessed excellent activity toward S. aureus and E. coli with inhibition zones of 26 mm and 32 mm, respectively. Besides, the biocompatibility and cytotoxicity of GA-HAP/N showed about 90% viability for McCoy cells with no sign of detachment after 72 h of treatment, while Saos-2 cells showed typical inhibition in growth associated with rounding off and detachment, signifying cytotoxicity. This selective toxicity induced by the drug-loaded GA-HAP might find application in drug delivery for precision medicine