Biomedical Coatings to Improve the Tissue-Biomaterial Interface

SiCxNyOz Coatings Enhance Endothelialization and Bactericidal activity and Reduce Blood Cell Activation

For biomedical applications, a number of ceramic coatings have been investigated, but the interactions with the components of living system remain unexplored for oxycarbonitride coatings. While addressing this aspect, the present study aims to provide an understanding of the biocompatibility of novel SiC_xN_yO_z coatings that could validate the hypothesis that such coatings may not only enhance the cell-material interaction by re-endothelialization but also can help to reduce bacterial adhesion and activation of blood cells. This work reports the physicochemical properties, hemocompatibility, endothelialization, and antibacterial properties of novel amorphous SiC_xN_yO_z coatings deposited on commercial pure titanium (Ti) by radiofrequency (RF) magnetron sputtering at varied nitrogen (N₂) flow rates. A comparison is made with diamond-like carbon (DLC) coatings, which are clinically used. The surface roughness, surface wettability, nanoscale hardness, and surface energy of SiC_xN_yO_z coatings were found to be dependent on the nitrogen (N₂) flow rate. Importantly, the as-deposited SiC_xN_yO_z coatings exhibited much better nanoscale hardness and scratch resistance than DLC coatings. Furthermore, Raman spectroscopy analysis of the SiC_xN_yO_z coating deposited on Ti showed a change in the graphitic/disordered carbon content. Cytocompatibility and hemocompatibility properties of the as-deposited SiC_xN_yO_z coating were evaluated using the Mus musculus lymphoid endothelial cell line (SVEC4-10) and rabbit blood in vitro. WST-1 assay analysis showed that these coatings, when compared to DLC, exhibited a better proliferation of endothelial cells, which can potentially result in improved surface endothelialization. Furthermore, qualitative and quantitative analyses of immunofluorescence images revealed a dense cellular layer of SVEC4-10 on SiC_xN_yO_z coatings, deposited at 15 and 30 sccm nitrogen flow rates. As far as compatibility with rabbit blood is concerned, the hemolysis of the SiC_xN_yO_z coatings was less than 4%, with slightly lower values for coatings deposited without N₂ flow. The SiC_xN_yO_z coatings support less platelet adhesion and aggregation, with no signature of morphological deformation, as compared to the uncoated titanium substrate or DLC coatings. Furthermore, SiC_xN_yO_z coatings were also found to be effectively extending the blood coagulation time for a period of 60 min. The antimicrobial study of as-deposited SiC_xN_yO_z coatings on E. coli and S. aureus bacteria revealed the effective inhibition of bacterial proliferation after 24 h of culture. An attempt has been made to explain the cyto- and hemocompatibility properties with antimicrobial efficacy of coatings in terms of the variation in the coating composition and surface energy. Taken together, we conclude that SiC_1.3N_0.76O_0.87 coating having a roughness of 17 nm and a surface free energy of 54.0 ± 0.7 mN/m can exhibit the best combination of hardness, elastic modulus, scratch resistance, cytocompatibility, hemocompatibility, and bactericidal properties.

Heparin-based and heparin-inspired hydrogels: size-effect, gelation and biomedical applications

The size-effect, fabrication methods and biomedical applications of heparin-based and heparin-inspired hydrogels are reviewed.

Clinical and Biomaterial Evaluation of a new Condensed Dual-Function Extracorporeal Circuit in Reoperation for Coronary Artery Bypass Surgery

Purpose

This prospective, randomized study compared the clinical performance of three types of circuits: a newly introduced, fully-coated, interchangeable open-closed circuit with a dual configuration (hard shell with a bypass shunt), reduced length, and reduced prime of less than 800 cc (CondECC); a completely coated circuit (ECC); and a similar uncoated, open circuit with standard length and prime (CONT).

Methods

75 patients undergoing reoperation for coronary revascularization were randomly allocated into three groups (N=25): Group 1: CondECC with shortened tubing, components and an open-closed configuration of low priming volume with a centrifugal pump and a shunt which bypassed the reservoir for closed configuration; Group 2: ECC with a roller pump and hard-shell reservoir; Group 3: CONT. Blood samples for CBC, inflammatory mediators [Interleukin-2 (IL-2), Complement-3a (C3a)] and flow cytometry (CD11 b/CD18) were collected after induction (T1) and heparin administration (T2), 15 min after cardiopulmonary bypass (CPB) (T3), before cessation of CPB (T4), 15 min after reversal (T5), and the first postoperative day (T6).

Results

Leukocyte counts demonstrated significant increases at T4, T5 in CONT but remained stable in ECC and CondECC (p<0.05). Platelets were preserved better at T4, T5 in both ECC and CondECC study groups (p<0.05). IL-2 and C3a levels were significantly lower at T3, T4, T5 in CondECC and T4, T5 in ECC (p<0.05). Blood protein adsorption analysis demonstrated increased amount of microalbumin on CONT fibers (p<0.05).

Conclusions

The CondECC is a flexible, dual-function, open/closed configuration system that was easy to use, safe and achieved better biocompatibility when compared to coated and uncoated conventional circuits.

Surface modification of Ti-6Al-4V alloy for biomineralization and specific biological response: Part I, inorganic modification

Titanium and its alloys represent the gold standard for orthopaedic and dental prosthetic devices, because of their good mechanical properties and biocompatibility. Recent research has been focused on surface treatments designed to promote their rapid osteointegration also in case of poor bone quality. A new surface treatment has been investigated in this research work, in order to improve tissue integration of titanium based implants. The surface treatment is able to induce a bioactive behaviour, without the introduction of a coating, and preserving mechanical properties of Ti6Al4V substrates (fatigue resistance). The application of the proposed technique results in a complex surface topography, characterized by the combination of a micro-roughness and a nanotexture, which can be coupled with the conventional macro-roughness induced by blasting. Modified metallic surfaces are rich in hydroxyls groups: this feature is extremely important for inorganic bioactivity (in vitro and in vivo apatite precipitation) and also for further functionalization procedures (grafting of biomolecules). Modified Ti6Al4V induced hydroxyapatite precipitation after 15 days soaking in simulated body fluid (SBF). The process was optimised in order to not induce cracks or damages on the surface. The surface oxide layer presents high scratch resistance.

Effect of poly(L-lactide) surface topography on the morphology of in vitro cultured human articular chondrocytes

Human articular chondrocytes were cultured in vitro on poly(L-lactic) acid, PLLA, substrates. Influence of the surface topography on cell morphology was found. Different surface microtopographies were obtained on PLLA by crystallizing at 120 degrees C after nucleation treatments that include isothermal stages at temperatures just below (55 degrees C) and just above (75 degrees C) the glass transition temperature (T(g) = 65 degrees C). Isothermal crystallization from the melt gave rise to big spherulites (approx. 50 microm diameter) with approx. 1 microm depth. Crystallization after nucleation treatments results in smaller (approx. 5 microm)-difficult to distinguish-spherulites. Cell viability was excellent and not affected by the surface roughness. Cell population on the nucleated samples resembles the result of culture on the reference tissue culture polystyrene (TCPS). However, cells cultured on big spherulites (PLLA isothermally crystallized without nucleation treatment) show a peculiar morphology, with a more isolated disposition and growth oriented in a characteristic direction.

In vitro and in vivo performance of a novel surface treatment to enhance osseointegration of endosseous implants

OBJECTIVE

This article shows the in vitro and in vivo characterization of a new biomimetic treatment developed to enhance the osseointegration of titanium dental implants.

STUDY DESIGN

A novel biomimetic treatment of titanium was developed. Its physicochemical properties and biologic and in vivo performance were considered and studied. Mineralization capability was assessed by soaking test in simulated body fluid solution, and cytocompatibility was assessed using osteoblast-like MG63 cell culture. Histomorphometric analysis was performed at 3 time points using a sheep animal model.

RESULTS

In vitro tests confirmed the biomimetic potential of the considered novel treatment. Histomorphometric analysis indicated its potential for rapid and good-quality osseointegration.

CONCLUSION

The in vitro and in vivo test results indicated that the proposed novel treatment possesses a significant potential to increase the rate of osteointegration of titanium for endosseous dental implants.

The integration of chitosan-coated titanium in bone: an in vivo study in rabbits

PROCEDURE

Much research is directed at surface modifications to enhance osseointegration of implants. A new potential coating is the biopolymer, chitosan, the deacetylated derivative of the natural polysaccharide, chitin. Chitosan is biocompatible, degradable, nontoxic, and exhibits osteogenic properties. The aim of this research was to investigate the hypothesis that chitosan-coated titanium supports bone formation and osseointegration.

MATERIALS AND METHODS

Chitosan (1 wt% of 92.3% deacetylated chitosan in 1% acetic acid) was solution cast and bonded to rough ground titanium pins (2-mm diameterx4-mm long) via silane reactions. Calcium phosphate sputter-coated titanium and uncoated titanium pins were used as controls. Two chitosan-coated pins, and 1 each of calcium phosphate coated and uncoated pins were implanted unilaterally in the tibia of 16 adult male New Zealand white rabbits. At 2, 4, 8, and 12 weeks, undecalcified sections were histologically evaluated for healing and bone formation.

RESULTS

Histological evaluations of tissues in contact with the chitosan-coated pins indicated minimal inflammatory response and a typical healing sequence of fibrous, woven bone formation, followed by development of lamellar bone. These observations were similar to those for tissues interfacing the control calcium phosphate-coated and uncoated titanium implants. Quantitative comparisons of the bone-implant interface were not possible since 31% of the implants migrated into the tibial marrow space after implantation due to insufficient cortical bone thickness to hold pins in place during healing.

CONCLUSION

These data support the hypothesis that chitosan-coatings are able to develop a close bony apposition or the osseointegration of dental/craniofacial and orthopedic implants.

Influence of recovering collagen with bioactive glass on osteoblast behavior

Bioactive ceramics have interesting properties from the biological standpoint, but their effects on cellular events remain partially unknown. In the current work, we investigated cellular viability, proliferation, and metabolic activity of rat primary osteoblasts in contact with four different samples: type I collagen, bioactive glass-coated collagen (GC), and both samples submitted to immersion for 5 days in a simulated body fluid. The bioactive glass coating was obtained from a sol-gel process. The cell viability, the alkaline phosphate, the collagen secretion, and the nitric oxide production by osteoblast were measured after 72 h of incubation in the presence of the samples. The GC that was immersed for 5 days in a simulated body fluid solution showed an increase in osteoblast viability and proliferation when it was compared with control and the other samples.

Surface and Bulk Contributions in the Crystallization Process of a Bioactive Glass

Bioactive glasses have attracted considerable interest in recent years. In this work, Differential Thermal Analysis (DTA) measurements were performed on bulk and powdered samples of the SiO2-Na2O-CaO-P2O5 glass system, in order to study the particle size effect on the crystal growth and nucleation process. A shift of the crystallization peak to lower temperatures and deconvolution of a slightly asymmetric crystallization peak into two separate peaks were observed with decreasing particle size. The bioactive behavior -through the process of immersion SBF- of the specific glass is studied as a function of particle size. A better bioactive response was observed increasing particle size until a specific size, further increase leading in no further improvement in the bioactive behavior.