Bioactive Surface Research Articles

Microstructures of Ti6Al4V matrices induce structural evolution of bioactive surface oxide layers via cold compression and induction heating

Considerable efforts have been devoted to the construction of micro- and nanostructured surfaces to improve the clinical application of Ti-based orthopedic implants. However, the preparation of bioactive microstructures with tunable characteristics remains challenging. Herein, we investigated the structural evolution of oxide layers on Ti6Al4V surfaces by conducting a cold compression and induction heating protocol. We found that the properties of the metallographic microstructures determined the size and structure of oxide crystallites formed via a seeding mechanism: the finer the matrix grains, the smaller the oxide crystallites. In addition, the alloy matrix grain sizes steadily increased with increasing axial compression because of recrystallization during induction heating. The formation of nanoscale rutile (TiO2) crystallites caused an increase of surface roughness and hardness, and considerably improved the bioactivity of Ti6Al4V, as measured by the degree of hydroxyapatite deposition in simulated body fluid in vitro. However, oversized oxide crystallites had a negative effect on the promotion of hydroxyapatite deposition. This important finding offers a feasible method for the controllable in-situ construction of bioactive oxide layers by designing the required matrix microstructures of Ti-based implant materials.

Fabrication of bioactive glass coating on pure titanium by sol-dip method: Dental applications.

This study aimed to assess the mechanical and biological properties of bioactive glass (BG) coating on titanium (Ti). Bioinert Ti substrates were coated by BG to induce bioactivity to the surface. The sol-gel derived BG 58S sol was successfully prepared and coated on the abraded and blasted Ti surface using the sol-dip method. The characterization and cell study for all substrates' surface was carried out. Adhesion test confirmed that a firmly adhered BG coating layer was formed on the abraded and blasted Ti. The measured bonding strength between the coating and the blasted Ti substrate was the highest among all samples, which was 41.03±2.31 MPa. In-vitro cell viability and alkaline phosphatase activity (ALP) tests results also showed that BG coating on the Ti substrate improved the biological properties of the surface. The BG sol-dip coating method could be used to fabricate Ti substrate with a bioactive surface.

Effect of laser cladded co-doped strontium fluorapatite nanopowder coating on the antibacterial and cell attachment of Ti-6Al-4V implants for bone applications

ABSTRACT In this study, doped strontium fluorapatite (Sr-FAP) nanopowders were synthesised by sol-gel and used as a coating to modify Ti-6Al-4V substrates through CO2 laser cladding. The Ca ions of FAP were substituted by a different amount of Sr ions to increase bone cell differentiation and antibacterial properties. Lattice parameters and crystal size values of different samples decrease with increasing the amount of Sr ion. According to the morphological results, the laser cladding Sr doped FAP nanopowders can create homogenously and crack-free coating on the Ti-6Al-4V substrates. The 0.6SrFAP nanopowder sample had a more hydrophilic nature in comparison to other Sr doped FAP nanopowders. This sample showed antibacterial properties and high cell adhesion, spreading, and viability while provided a bioactive and favourable surface for bone tissue regeneration. Therefore, 0.6SrFAP nanopowder laser cladding on the surface of Ti-6Al-4VV implants seems to be promising for further in-vivo investigations in bone applications.

Influence of altered Ca-P based electrolytes on the anodised titanium bioactivity

Abstract Anodic oxidation (AO) of titanium is a common electrochemical process for surface modification of metallic surfaces and is conducted in an electrolyte solution. Anodisation of titanium implants can generate a coating with optimal characteristics to accelerate the growth of bone-like apatite. The present work aims to develop a novel AO electrolyte formulation of a Ca P base solution containing three different alteration agents. The characteristics of the anodised coating were modified by varying the volume fractions of the alteration agents, namely sulphuric acid, hydrogen peroxide, and acetic acid in a base solution of β-glycerolphosphate disodium salt pentahydrate (β-GP) and calcium acetate monohydrate (CA). The surface morphology, mineralogy, wettability, and bioactivity of these coatings were analysed using scanning electron microscopy (SEM), X-ray diffraction (XRD), contact angle analysis, and in vitro testing using simulated body fluid (SBF). Anodisation in a mixture of β-GP + CA electrolyte resulted in the formation of Ca-P-rich oxide coating (with surface features with a donut-like shape) and when altered with 12.5 vol% sulphuric acid, highly defined spiky needle-like morphology was seen on the surface. These coatings were composed of hydroxyapatite, tricalcium phosphate, and calcium diphosphate. After 7 days of SBF immersion, the surface was observed to contain a dense layer of bone-like apatite. However, alteration using acetic acid did not result in any significant changes to the surface characteristics and no bone-like apatite formation was observed even after soaking in SBF for 7 days. Alteration using hydrogen peroxide resulted in an anodised coating that assisted the growth of bone-like apatite layer on the coating surfaces after soaking in SBF for 7 days. The differences in coating performance are linked to the presence of different functional ions with hydronium groups (from sulphuric acid) being superior compared to the carboxyl ions (from acetic acid). The coating produced by sulphuric acid alteration demonstrated super hydrophilicity and rougher topographies which are ideal characteristics for cell attachment and proliferation in implant applications.

Visual and antibacterial magnesium implants with low biocorrosion and bioactive surface for in vivo tracking and treating MRSA infection

• A multifunctional bioactive visual Mg-based implant (Mg@PCS) was fabricated facilely. • Mg@PCS possesses biodegradation/photoluminescence/osteogenic activity/antiinfection. • Mg@PCS implants could be tracked by fluorescence and treating MRSA infection in vivo . Magnesium (Mg) have a promising potential in orthopedic implantations and bone regeneration due to their biodegradation and resemblance modulus to native bone. However, the rapid corrosion/bacterial infection/single function probably limits their application. Herein, we utilized a facile surface self-assembly method to construct a multifunctional elastomeric bioactive poly(citrate-silicon) (PCS) coating on Mg through the ion bonding interaction (–COO-Mg) to obtain the Mg@PCS implants. Compared to the conventional Mg, Mg@PCS implants possess representative multifunctional properties including high corrosion resistance, low degradation and stable pH environment, controlled photoluminescence, robust antibacterial activity, enhanced cytocompatibility and osteogenic differentiation ability. The in vivo results suggested that Mg@PCS showed fluorescence-tracking ability, and could efficiently reduce the inflammatory response and treat the infection of methicillin-resistant Staphylococcus aureus ( MRSA ). This work probably provides a reasonable strategy to develop visual bioactive implants with antiinfection for regenerative medicine.

Race to invade: Understanding soft tissue integration at the transmucosal region of titanium dental implants

ObjectivesThe success of a dental implant system not only depends on appropriate osseointegration at the bone-implant interface, but also on robust soft-tissue integration (STI)/muco-integration at the transmucosal region. However, numerous studies have reported that the STI quality of conventional smooth and bio-inert titanium-based transmucosal components is significantly inferior to that of natural teeth, which may compromise the long-term success of implant restorations. In this review article, we discuss the structural and histological characteristics of peri-implant tissues; compare the roles of various cells residing in the transmucosal region and explore the material-based challenges that must be addressed to achieve early establishment and long-term maintenance of STI. MethodsThis extensive review article critically compares and contrasts the findings from articles published in the domain of ‘soft-tissue integration around Ti dental implants’. ResultsHistological characteristics, including poorer epithelial attachment and absence of direct collagen-implant/abutment integration, are responsible for the inferior STI strength around dental implants/abutments. Furthermore, various cellular functions during STI establishment and maturation at the abutment-mucosa interface must be modulated to achieve early STI. Moreover, we discuss and detail the challenges of achieving robust STI, including the presence of oral bacterial milieu, as well as material and corrosion related issues. Finally, research challenges towards achieving and maintaining robust STI are discussed, targeting the future directions to enhance the long-term survival of implant restorations. SignificanceBased on its histological characteristics, STI on current implant/abutment surfaces is suboptimal compared to the periodontal attachment found at teeth, making implants potentially more susceptible to disease initiation and progression. To obtain stable STI at the trasmucosal region, it is essential for future studies to design customized implant systems, with enhanced surface bioactivity and tailorable therapeutic capacity, which can improve the long-term success of implant restorations, especially in compromised conditions.

Amino Acid-Based Imidazole Ionic Liquid: A Novel Soft Matrix for Electrochemical Biosensing Applications

A new amino acid-based ionic liquid of 1-methyl-3-dodecane imidazolium aspartic acid ([Cₙmim]Asp IL, n = 4, 6, 8, 12, 14) was reported as a soft matrix to be used as a novel electrochemical glucose biosensor. [Cₙmim]Asp ILs were synthesized using a simple acid–base titration method and characterized by nuclear magnetic resonance spectroscopy, Fourier transform infrared (FT-IR) spectrum, scanning electron microscopy, negative-staining and cryogenic transmission electron microscopy, electrical conductivity, surface tension, dynamic light scattering, and UV–vis spectrum. [Cₙmim]Asp ILs possessed excellent conductivity and a large specific surface area, providing a biocompatible microenvironment to promote enzyme-catalyzed direct electron transfer while maintaining surface bioactivity and stability. It was found that the micelle structure could form in the [C₁₂mim]Asp IL solution when the concentration was beyond its critical micelle concentration. Glucose oxidase (GOx) could be uniformly dispersed and immobilized onto these micelles of the [C₁₂mim]Asp IL soft matrix through a hydrogen bond and physical absorption. Electrochemical experiments demonstrated that [C₁₂mim]Asp/GOx/Nafion/GCE achieved the best electrochemical performance toward glucose at a working potential of −0.33 V. The [C₁₂mim]Asp-based enzyme sensor displays a linear range response to glucose concentration from 0.001 to 0.58 and 0.58 to 12 mM and a low-end detection limit of 0.572 μM (S/N = 3). Additionally, the present glucose biosensor is robust to interfering molecules and shows acceptable reproducibility and practical application for real samples. The proposed amino acid-based ionic liquid can serve as a versatile and promising soft immobilization matrix for development of excellent biosensor applications.

Citric acid functionalized nitinol stent surface promotes endothelial cell healing.

While drug-eluting stents containing anti-proliferative agents inhibit proliferation of smooth muscle cells (SMCs), they also delay the regrowth of the endothelial cells which can result in subsequent development of restenosis. Acidic extracellular environments promote cell anchorage and migration by inducing conformational change in integrins, the main cell adhesion proteins. This study addresses the feasibility of a citric acid (CA) functionalized nitinol stent for improving vascular biocompatibility, specifically enhancing endothelialization. CA functionalized nitinol vascular stents are compared to commercial bare metal (Zilver Flex) and paclitaxel eluting stents (Zilver PTX) in terms of re-endothelialization. To study the effect of stent coatings, a stent conditioned media methodology was developed in an attempt to represent in vivo conditions. Overall, distinct advantages of the CA functionalized nitinol stent over commercial Zilver PTX DES and Zilver Flex BMS stents in terms of endothelial cell adhesion, migration, and proliferation are reported. These novel findings indicate the potential of a CA functionalized stent to serve as a bioactive and therapeutic surface for re-endothelialization, perhaps in combination with a SMC proliferation inhibitor coating, to prevent restenosis.

Lignin-based thermoresponsive macromolecules via vitamin-induced metal-free ATRP

An environmentally-friendly process for the modification of lignin with thermoresponsive polymers was employed, providing well-defined structures with narrow molecular weight distribution (Mw/Mn = 1.44). We report a biocompatible vitamin-inspired photoinitiation system composed of two components i.e. riboflavin (vitamin B2) as a photosensitizer and ascorbic acid (vitamin C) as a mild reducing agent. Under blue light LEDs irradiation at 460 nm (5.0 mW cm−2) the presented two-component photoinitiation setup enables grafting of poly(ethylene glycol) methyl ether methacrylate (OEGMA500) from brominated lignin via metal-free ATRP approach. A series of cyclic voltammetry (CV) measurements were conducted to electrochemically characterize ATRP initiators, both brominated lignin and lignin-based polymers, confirming preserved chain-end functionality of the prepared macromolecules. Received polymers with lignin core and POEGMA side chains exhibited thermoresponsive properties, which were investigated by determination of number average sizes of macromolecules by dynamic light scattering (DLS) and transmittance by ultraviolet/visible (UV-Vis) absorption spectroscopy of KL-g-(POEGMA-Br)10 aqueous solution. The in vitro curcumin release studies showed that the active substance is released from drug-loaded micelles in a thermo-sensitive manner. Prepared lignin-based macromolecules will show wide application as crucial components of thermoresponsive coatings, potentially creating bioactive surfaces characterized by antifouling properties, controlling cell adhesion or used as biosensors, due to PEG-containing side chains in branched polymers.

Polydopamine–Ag composite surface guides HBMSCs adhesion and proliferation

Human bone marrow mesenchymal stem cells (HBMSCs) are regarded as an important resource in the field of maxillofacial bone regeneration because of their favorable properties when compared with other stem cells. Hence, finding suitable materials that could extend the application of HBMSCs has become an emerging medical topic and socioeconomic problem. In this work, polydopamine (PDA)–Ag surface was fabricated by PDA assisted photoreduction method, and the obtained PDA–Ag composite surface significantly promoted HBMSCs adhesion and proliferation. This effect is highly related to the amount of Ag nanoparticles (Ag NPs) present on the PDA surface. The behavior of HBMSCs on PDA–Ag surface could be spatially manipulated by controlling the distribution of Ag NPs on PDA surface (by controlling UV light). The general adhesion property allows the PDA–Ag surface to be fabricated on various substrates, making it a simple, general and controllable method for the fabrication of bioactive surface for HBMSCs.

Investigation of in vitro behavior of plasma sprayed Ti, TiO2 and HA coatings on PEEK

Orthopedic implants are one of the most reliable and widely used equipments to increase the quality of human life by enhancing or replacing damaged body parts and ensuring the problematic parts of the body to become operative after a short time period. Polyether ether ketone (PEEK) is a semi-crystal high-performance thermoplastic polymeric implant material which emerged as an alternative for metallic implants that used in orthopedic surgery. Although PEEK has some superior properties such as high melting point, superb wear resistance, excellent fatigue behavior, non-toxicity for bone tissue and elasticity modulus similar to human bone, PEEK has some disadvantages such as biologically inert behavior and low bioactivity. In this context, coating the implant surface to improve its osteointegration behavior is widely accepted. Coating PEEK polymers with bioactive materials such as Hydroxyapatite (HA) is among one of the solutions for this problem. In this study, in order to increase surface bioactivity of PEEK biomaterials, Titanium (Ti), Titanium dioxide (TiO2) and Hydroxyapatite (HA) powder combinations was coated on PEEK samples by using Atmospheric Plasma Spray (APS) method. Morphological and chemical characterization showed produced coatings are suitable for implantation process. Also in vitro tests performed in Simulated Body Fluid (SBF) revealed that HA, Ti + HA and TiO2 + HA coatings have bioactive property.

Copper-containing bioactive glass/PVA membranes for guided bone regeneration

The purpose of this paper was to produce CuO-containing bioactive glass/PVA membranes with osteogenic and antibacterial properties to use as a membrane barrier for guided bone regeneration (GBR). The composite membranes were obtained by aqueous tape casting using PVA and a sol-gel-derived bioactive glass composed of 60% SiO2∙(36-x)% CaO∙4% P2O5∙x% CuO (mol %), where x = 0, 1 and 3%. The tape casting process could not show changes either in the composition of the glass or in its structure. When immersed in SFB, all composite membranes showed ability to form an apatite layer. The presence of CuO in the membranes improved the osteoblastic proliferation along with a higher damage to the bacteria membrane. Considering their low swelling rate, important surface bioactivity and low level degradation over time, these membranes meet the basic requirements to act as a GBR barrier, while demonstrating a high ability to control the bacteria growth.

A comparative study on silicon nitride, titanium and polyether ether ketone on mouse pre-osteoblast cells.

The current study provides more insights about the surface bioactivity of the silicon nitride (Si3N4) as a potential candidate for bone regeneration in craniofacial and orthopaedic applications compared with conventional implantation materials. Current skeletal reconstructive materials such as titanium and polyether ether ketone (PEEK) are limited by poor long-term stability, biocompatibility and prolonged healing. Si3N4 is an FDA-approved material for an intervertebral spacer in spinal fusion applications. It is biocompatible and has antimicrobial properties. Here, we hypothesize that Si3N4 was found to be an osteoconductive material and conducts the growth, differentiation of MC3T3-E1 cells for extracellular matrix deposition, mineralization and eventual bone regeneration for craniofacial and orthopaedic applications. MC3T3-E1 cells were used to study the osteoblastic differentiation and mineralization on sterile samples of Si3N4, titanium alloy and PEEK. The samples were then analysed for extracellular matrix deposition and mineralization by FTIR, Raman spectroscopy, SEM, EDX, Alizarin Red, qRT-PCR and ELISA. The in vitro study indicates the formation of collagen fibres and mineral deposition on all three sample surfaces. There was more profound and faster ECM deposition and mineralization on Si3N4 surface as compared to titanium and PEEK. The FTIR and Raman spectroscopy show formation of collagen and mineral deposition at 30 days for Si3N4 and titanium and not PEEK. The peaks shown by Raman for Si3N4 resemble closely to natural bone. Results also indicate the upregulation of osteogenic transcription factors such as RUNX2, SP7, collagen type I and osteocalcin. The authors concluded that Si3N4 rapidly conducts mineralized tissue formation via extracellular matrix deposition and biomarker expression in mouse calvarial pre-osteoblast cells. Thus, this study confirms that the bioactive Si3N4 could be a potential material for craniofacial and orthopaedic applications leading to rapid bone regeneration that resemble the natural bone structure.

Cellular signaling cross-talk between different cardiac cell populations: an insight into the role of exosomes in the heart diseases and therapy.

Exosomes are a subgroup of extracellular bilayer membrane nanovesicles that are enriched in a variety of bioactive lipids, receptors, transcription factors, surface proteins, DNA, and noncoding RNAs. They have been well recognized to play essential roles in mediating intercellular signaling by delivering bioactive molecules from host cells to regulate the physiological processes of recipient cells. In the context of heart diseases, accumulating studies have indicated that exosome-carried cellular proteins and noncoding RNA derived from different types of cardiac cells, including cardiomyocytes, fibroblasts, endothelial cells, immune cells, adipocytes, and resident stem cells, have pivotal roles in cardiac remodeling under disease conditions such as cardiac hypertrophy, diabetic cardiomyopathy, and myocardial infarction. In addition, exosomal contents derived from stem cells have been shown to be beneficial for regenerative potential of the heart. In this review, we discuss current understanding of the role of exosomes in cardiac communication, with a focus on cardiovascular pathophysiology and perspectives for their potential uses as cardiac therapies.

Fouling in ocular devices: implications for drug delivery, bioactive surface immobilization, and biomaterial design.

The last 30years has seen a proliferation of research on protein-resistant biomaterials targeted at designing bio-inert surfaces, which are prerequisite for optimal performance of implantable devices that contact biological fluids and tissues. These efforts have only been able to yield minimal results, and hence, the ideal anti-fouling biomaterial has remained elusive. Some studies have yielded biomaterials with a reduced fouling index among which high molecular weight polyethylene glycols have remained dominant. Interestingly, the field of implantable ocular devices has not experienced an outflow of research in this area, possibly due to the assumption that biomaterials tested in other body fluids can be translated for application in the ocular space. Unfortunately, progression in the molecular understanding of many ocular conditions has brought to the fore the need for treatment options that necessitates the use of anti-fouling biomaterials. From the earliest implanted horsehair and silk seton for glaucoma drainage to the recent mini telescopes for sight recovery, this review provides a concise incursion into the gradual evolution of biomaterials for the design of implantable ocular devices as well as approaches used to overcome the challenges with fouling. The implication of fouling for drug delivery, the design of immune-responsive biomaterials, as well as advanced surface immobilization approaches to support the overall performance of implantable ocular devices are also reviewed.

An In-Vitro Analysis of Peri-Implant Mucosal Seal Following Photofunctionalization of Zirconia Abutment Materials

The presence of epithelial and connective tissue attachment at the peri-implant–soft tissue region has been demonstrated to provide a biological barrier of the alveolar bone from the oral environment. This barrier can be improved via surface modification of implant abutment materials. The effect of photofunctionalization on creating a bioactive surface for the enhancement of the epithelial and connective tissue attachment of zirconia implant abutment’s peri-implant mucosal interface using organotypic model has not been investigated. Therefore, this study aimed to evaluate the soft tissue seal around peri-implant mucosa and to understand the effect of photofunctionalization on the abutment materials. Three types of abutment materials were used in this study; yttria-stabilized zirconia (YSZ), alumina-toughened zirconia, and grade 2 commercially pure titanium (CPTi) which were divided into nontreated (N-Tx) and photofunctionalized group (UV-Tx). The three-dimensional peri-implant mucosal model was constructed using primary human gingival keratinocytes and fibroblasts co-cultured on the acellular dermal membrane. The biological seal was determined through the concentration of tritiated water permeating the material–soft tissue interface. The biological seal formed by the soft tissue in the N-Tx group was significantly reduced compared to the UV-treated group (p < 0.001), with YSZ exhibiting the lowest permeability among all materials. Photofunctionalization of implant abutment materials improved the biological seal of the surrounding soft tissue peri-implant interface.

Development and Characterization of Biomedical Porous Ti–20Nb–5Ag Alloy: Microstructure, Mechanical Properties, Surface Bioactivity and Cell Viability Studies

In this study, antibacterial Ag element added to synthesis of porous Ti–20Nb–5Ag (wt%) alloy using powder metallurgy space holder route. The microstructural, mechanical property, surface bioactivity and cytotoxicity behavior of porous Ti–20Nb–5Ag alloy have been investigated. The developed porous alloy obtained the porosities ranging from 22.5 to 68%. The porous sample having a porosity of about 43% is found to be in the optimum condition, which possess a modulus of about 5.8 GPa with an excellent compressive strength about 205 MPa. XRD result shows that the formation of small amount of α-Ti, β-Ti, along with α״ martensite and Ti2Ag are key phase constituents of sintered porous Ti–20Nb–5Ag alloys. The compression strength and elastic modulus of the sintered alloys were showed that decreased with increase of porosity. Surface bioactivity result revealed that the significant formation of hydroxyapatite on the alkali-heat treated (5 M NaOH) porous Ti–20Nb–5Ag alloy which is found after the in vitro test in SBF. Further, the cell viability test was conducted on as-synthesized porous Ti–20Nb–5Ag alloy for 1, 4, and 7 days using MG-63 human osteoblast cells and result shows an excellent cell proliferation, and the cytotoxicity test confirms the non-toxic nature of the porous alloy which is very much suitable for implant application.

In vitro evaluation of electrochemically bioactivated Ti6Al4V 3D porous scaffolds

Triply periodic minimal surfaces (TPMS) are known for their advanced mechanical properties and are wrinkle-free with a smooth local topology. These surfaces provide suitable conditions for cell attachment and proliferation. In this study, the in vitro osteoinductive and antibacterial properties of scaffolds with different minimal pore diameters and architectures were investigated. For the first time, scaffolds with TPMS architecture were treated electrochemically by plasma electrolytic oxidation (PEO) with and without silver nanoparticles (AgNPs) to enhance the surface bioactivity. It was found that the scaffold architecture had a greater impact on the osteoblast cell activity than the pore size. Through control of the architecture type, the collagen production by osteoblast cells increased by 18.9% and by 43.0% in the case of additional surface PEO bioactivation. The manufactured scaffolds demonstrated an extremely low quasi-elastic modulus (comparable with trabecular and cortical bone), which was 5–10 times lower than that of bulk titanium (6.4–11.4 GPa vs 100–105 GPa). The AgNPs provided antibacterial properties against both gram-positive and gram-negative bacteria and had no significant impact on the osteoblast cell growth. Complex experimental results show the in vitro effectiveness of the PEO-modified TPMS architecture, which could positively impact the clinical applications of porous bioactive implants.

Micro-Nano Surface Characterization and Bioactivity of a Calcium Phosphate-Incorporated Titanium Implant Surface.

The surface topography of dental implants and micro-nano surface characterization have gained particular interest for the improvement of the osseointegration phases. The aim of this study was to evaluate the surface micro-nanomorphology and bioactivity (apatite forming ability) of Ossean® surface, a resorbable blast medium (RBM) blasted surface further processed through the incorporation of a low amount of calcium phosphate. The implants were analyzed using environmental scanning electronic microscopy (ESEM), connected to Energy dispersive X-ray spectroscopy (EDX), field emission gun SEM-EDX (SEM-FEG) micro-Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) before and after immersion in weekly refreshed Hank’s balanced salt solution (HBSS) for 28 days. The analysis of the samples before immersion showed a moderately rough surface, with micropits and microgrooves distributed on all of the surface; EDX microanalysis revealed the constitutional elements of the implant surface, namely titanium (Ti), aluminum (Al) and vanadium (V). Limited traces of calcium (Ca) and phosphorous (P) were detected, attributable to the incorporated calcium phosphate. No traces of calcium phosphate phases were detected by micro-Raman spectroscopy. ESEM analysis of the implant aged in HBSS for 28 days revealed a significantly different surface, compared to the implant before immersion. At original magnifications <2000×, a homogeneous mineral layer was present on all the surface, covering all the pits and microgrooves. At original magnifications ≥10,000×, the mineral layer revealed the presence of small microspherulites. The structure of these spherulites (approx. 2 µm diameter) was observed in nanoimmersion mode revealing a regular shape with a hairy-like contour. Micro-Raman analysis showed the presence of B-type carbonated apatite on the implant surface, which was further confirmed by XPS analysis. This implant showed a micro-nano-textured surface supporting the formation of a biocompatible apatite when immersed in HBSS. These properties may likely favor bone anchorage and healing by stimulation of mineralizing cells.

Preparation and characterization of ferulic acid-modified water soluble chitosan and poly (γ-glutamic acid) polyelectrolyte films through layer-by-layer assembly towards protein adsorption

In this study, ferulic acid-modified water soluble chitosan and poly (γ-glutamic acid) polyelectrolyte multilayers films were constructed through the layer-by-layer (LBL) self-assembly technique. Chitosan (CS) or ferulic acid modified chitosan (MCS) and Poly (γ-glutamic acid) (PGA) was alternately deposited on the surface of glass substrate for the enhancement of surface modification. The obtained films were characterized by Fourier transform spectroscopy (FTIR), X-ray diffractometry (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), UV–vis spectroscopy and water contact angle to study its physico-chemical properties including protein absorption. The (PGA/MCS) films showed intense deposition of multilayers built upon the surface roughness and an increase in the exponential growth of multilayer films by UV–vis spectroscopy. Water contact angle indicated that the (PGA/MCS) films performed well with good wettability due to the increase in the number of layers. The LBL multilayer coatings of (PGA/MCS) films surface possessed a reduced amount of protein adsorption. These results indicated that it can resist the protein adsorption and can enhance the biocompatibility towards the biomedical application through the protein interaction. The (PGA/MCS) films has the potential to utilization as a good biomaterial for biomedical purposes to intensify the bio-active surface.