Long-term sustained release of salicylic acid from cross-linked biodegradable polyester induces a reduced foreign body response in mice.

There has been a continuous surge toward developing new biopolymers that exhibit better in vivo biocompatibility properties in terms of demonstrating a reduced foreign body response (FBR). One approach to mitigate the undesired FBR is to develop an implant capable of releasing anti-inflammatory molecules in a sustained manner over a long time period. Implants causing inflammation are also more susceptible to infection. In this article, the in vivo biocompatibility of a novel, biodegradable salicylic acid releasing polyester (SAP) has been investigated by subcutaneous implantation in a mouse model. The tissue response to SAP was compared with that of a widely used biodegradable polymer, poly(lactic acid-co-glycolic acid) (PLGA), as a control over three time points: 2, 4, and 16 weeks postimplantation. A long-term in vitro study illustrates a continuous, linear (zero order) release of salicylic acid with a cumulative mass percent release rate of 7.34 × 10(-4) h(-1) over ∼1.5-17 months. On the basis of physicochemical analysis, surface erosion for SAP and bulk erosion for PLGA have been confirmed as their dominant degradation modes in vivo. On the basis of the histomorphometrical analysis of inflammatory cell densities and collagen distribution as well as quantification of proinflammatory cytokine levels (TNF-α and IL-1ß), a reduced foreign body response toward SAP with respect to that generated by PLGA has been unambiguously established. The favorable in vivo tissue response to SAP, as manifest from the uniform and well-vascularized encapsulation around the implant, is consistent with the decrease in inflammatory cell density and increase in angiogenesis with time. The above observations, together with the demonstration of long-term and sustained release of salicylic acid, establish the potential use of SAP for applications in improved matrices for tissue engineering and chronic wound healing.

Osteogenesis, hemocompatibility, and foreign body response of polyvinylidene difluoride-based composite reinforced with carbonaceous filler and higher volume of piezoelectric ceramic phase.

Hybrid polymer-ceramic composites have been widely investigated for bone tissue engineering applications. The incorporation of a large amount of inorganic phase, like barium titanate (BaTiO3) with good dispersion, in a polymeric matrix using a conventional processing approach has always been challenging. Also, the comprehensive study encompassing the interactions of key components of living organisms (cell, blood, tissue) with such hybrid composites is not well explored in many published studies. Built on our earlier studies and recognizing the importance of poly(vinylidene fluoride) (PVDF) as a widely used polymer for a wide spectrum of biomedical applications, the present study reports the qualitative and quantitative analysis of the biocompatibility of PVDF composite (PVDF/30BT/3MWCNT) reinforced with large amounts of BaTiO3 (30 wt %) and tailored addition of multiwalled carbon nanotubes (MWCNT; 3 wt %). The melt mixing-extrusion-compression moulding-based processing approach resulted in an enhancement of ß-phase content, thermal stability, and wettability in the semi-crystalline PVDF composite. The enhanced hemocompatibility of PVDF/30BT/3MWCNT has been established conclusively by a series of in vitro blood-material interaction assays, including haemolysi, analysis of platelets attachment and activation, dynamic blood coagulation, and plasma recalcification time. The cytocompatibility study confirms an improved adhesion, proliferation, and migration of osteoprogenitor cells (preosteoblasts; MC3T3-E1) on PVDF/30BT/3MWCNT, in a manner better than neat PVDF, in vitro. When these cells were cultured in osteogenic differentiating media, the modulated osteogenesis, in terms of alkaline phosphatase activity, intracellular Ca2+ concentration, and calcium deposition on the PVDF/30BT/3MWCNT, was recorded. Following subcutaneous implantation of PVDF/30BT/3MWCNT in rat model, no apparent variation was recorded in the complete hemogram (blood hematology analysis) or serum biochemistry, post 30-, 60-, and 90-days surgery. Importantly, 90-days post-implantation, the fibrous capsule thickness was significantly reduced in the composites w.r.t PVDF alone, together with better blood vessel formation, indicating improved neovascularization around the composite. This study establishes the efficacy of inorganic fillers in enhancing the biocompatibility of PVDF, which could open up a wide range of biomedical applications.

Electrical field stimulated modulation of cell fate of pre-osteoblasts on PVDF/BT/MWCNT based electroactive biomaterials.

The present study reports the impact of the interplay between electroactive properties of the biomaterials and electrical stimulation (ES) toward the cell proliferation, migration and maturation of osteoprogenitors (preosteoblasts; MC3T3-E1) on the electroactive poly (vinylidene difluoride) (PVDF)-based composites. The barium titanate (BaTiO3; BT; 30 wt%) and multiwalled carbon nanotubes (MWCNT; 3 wt%) were introduced into the PVDF via melt mixing, which led to an enhancement of the dielectric permittivity, electrical conductivity, and surface roughness. We also present the design and development of an in-house customized 12-well plate-based device for providing different types (DC, square, biphasic) of ES to cells in culture in a programmable manner. In the presence of ES of 1 V cm-1 , biophysical stimulation experiments performed using 12-well plate-based device revealed that PVDF composite (PVDF/30BT/3MWCNT) can facilitate the enhanced adhesion and proliferation of the MC3T3-E1 in non-osteogenic media, with respect to non-stimulated conditions. Importantly, MC3T3-E1 cells demonstrated significantly better migration and differentiation on the PVDF/30BT/3MWCNT under ES when compared to ES-free culture conditions. Similar enhancement with respect to alkaline phosphatase activity, intracellular Ca2+ concentration, and calcium deposition in MC3T3-E1 cells was recorded, when pre-osteoblasts were grown for 21 days on electroactive substrates. All these observations supported the activation of osteo-differentiation fates, which were further promoted in the osteogenic medium. The present study demonstrates that the synergistic interactions of ES with piezoelectric PVDF-based polymer composite can potentially enhance the proliferation, migration, and osteogenesis of the pre-osteoblast cells, rendering it a promising bioengineering strategy for bone tissue engineering.

Evaluation of implant properties, safety profile and clinical efficacy of patient-specific acrylic prosthesis in cranioplasty using 3D binderjet printed cranium model: A pilot study.

There exists a significant demand to develop patient-specific prosthesis in reconstruction of cranial vaults after decompressive craniectomy. we report here, the outcomes of an unicentric pilot study on acrylic cranial prosthesis fabricated using a 3D printed cranium model with its clinically relevant mechanical properties. METHODS: The semi-crystalline polymethyl methacrylate (PMMA) implants, shaped to the cranial defects of 3D printed cranium model, were implanted in 10 patients (mean age, 40.8 ± 14.8 years). A binderjet 3D printer was used to create patient-specific mould and PMMA was casted to fabricate prosthesis which was analyzed for microstructure and properties. Patients were followed up for allergy, infection and cosmesis for a period of 6 months. RESULTS: As-cast PMMA flap exhibited hardness of 15.8 ± 0.24Hv, tensile strength of 30.7 ± 3.9 MPa and elastic modulus of 1.5 ± 0.1 GPa. 3D microstructure of the semi-crystalline acrylic implant revealed 2.5-15 µm spherical isolated pores. The mean area of the calvarial defect in craniectomy patients was 94.7 ± 17.4 cm2. We achieved a cranial index of symmetry (CIS -%) of 94.5 ± 3.9, while the average post-operative Glasgow outcome scale (GOS) score recorded was 4.2 ± 0.9. CONCLUSIONS: 3D printing based patient-specific design and fabrication of acrylic cranioplasty implant is safe and achieves acceptable cosmetic and clinical outcomes in patients with decompressive craniectomy. Our study ensured clinically acceptable structural and mechanical properties of implanted PMMA, suggesting that a low cost 3D printer based PMMA flap is an affordable option for cranioplasty in resource constrained settings.

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 SiCxNyOz 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 SiCxNyOz 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 SiCxNyOz coatings were found to be dependent on the nitrogen (N2) flow rate. Importantly, the as-deposited SiCxNyOz coatings exhibited much better nanoscale hardness and scratch resistance than DLC coatings. Furthermore, Raman spectroscopy analysis of the SiCxNyOz coating deposited on Ti showed a change in the graphitic/disordered carbon content. Cytocompatibility and hemocompatibility properties of the as-deposited SiCxNyOz 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 SiCxNyOz coatings, deposited at 15 and 30 sccm nitrogen flow rates. As far as compatibility with rabbit blood is concerned, the hemolysis of the SiCxNyOz coatings was less than 4%, with slightly lower values for coatings deposited without N2 flow. The SiCxNyOz coatings support less platelet adhesion and aggregation, with no signature of morphological deformation, as compared to the uncoated titanium substrate or DLC coatings. Furthermore, SiCxNyOz coatings were also found to be effectively extending the blood coagulation time for a period of 60 min. The antimicrobial study of as-deposited SiCxNyOz 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 SiC1.3N0.76O0.87 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.

Biomimetic porous high-density polyethylene/polyethylene- grafted-maleic anhydride scaffold with improved in vitro cytocompatibility.

A major challenge for tissue engineering is to design and to develop a porous biocompatible scaffold, which can mimic the properties of natural tissue. As a first step towards this endeavour, we here demonstrate a distinct methodology in biomimetically synthesized porous high-density polyethylene scaffolds. Co-extrusion approach was adopted, whereby high-density polyethylene was melt mixed with polyethylene oxide to form an immiscible binary blend. Selective dissolution of polyethylene oxide from the biphasic system revealed droplet-matrix-type morphology. An attempt to stabilize such morphology against thermal and shear effects was made by the addition of polyethylene- grafted-maleic anhydride as a compatibilizer. A maximum ultimate tensile strength of 7 MPa and elastic modulus of 370 MPa were displayed by the high-density polyethylene/polyethylene oxide binary blend with 5% maleated polyethylene during uniaxial tensile loading. The cell culture experiments with murine myoblast C2C12 cell line indicated that compared to neat high-density polyethylene and high-density polyethylene/polyethylene oxide, the high-density polyethylene/polyethylene oxide with 5% polyethylene- grafted-maleic anhydride scaffold significantly increased muscle cell attachment and proliferation with distinct elongated threadlike appearance and highly stained nuclei, in vitro. This has been partly attributed to the change in surface wettability property with a reduced contact angle (∼72°) for 5% PE- g-MA blends. These findings suggest that the high-density polyethylene/polyethylene oxide with 5% polyethylene- grafted-maleic anhydride can be treated as a cell growth substrate in bioengineering applications.

Modulation of Protein Adsorption and Cell Proliferation on Polyethylene Immobilized Graphene Oxide Reinforced HDPE Bionanocomposites.

The uniform dispersion of nanoparticles in a polymer matrix, together with an enhancement of interfacial adhesion is indispensable toward achieving better mechanical properties in the nanocomposites. In the context to biomedical applications, the type and amount of nanoparticles can potentially influence the biocompatibility. To address these issues, we prepared high-density polyethylene (HDPE) based composites reinforced with graphene oxide (GO) by melt mixing followed by compression molding. In an attempt to tailor the dispersion and to improve the interfacial adhesion, we immobilized polyethylene (PE) onto GO sheets by nucleophilic addition-elimination reaction. A good combination of yield strength (ca. 20 MPa), elastic modulus (ca. 600 MPa), and an outstanding elongation at failure (ca. 70%) were recorded with 3 wt % polyethylene grafted graphene oxide (PE-g-GO) reinforced HDPE composites. Considering the relevance of protein adsorption as a biophysical precursor to cell adhesion, the protein adsorption isotherms of bovine serum albumin (BSA) were determined to realize three times higher equilibrium constant (Keq) for PE-g-GO-reinforced HDPE composites as compared to GO-reinforced composites. To assess the cytocompatibility, we grew osteoblast cell line (MC3T3) and human mesenchymal stem cells (hMSCs) on HDPE/GO and HDPE/PE-g-GO composites, in vitro. The statistically significant increase in metabolically active cell over different time periods in culture for up to 6 days in MC3T3 and 7 days for hMSCs was observed, irrespective of the substrate composition. Such observation indicated that HDPE with GO or PE-g-GO addition (up to 3 wt %) can be used as cell growth substrate. The extensive proliferation of cells with oriented growth pattern also supported the fact that tailored GO addition can support cellular functionality in vitro. Taken together, the experimental results suggest that the PE-g-GO in HDPE can effectively be utilized to enhance both mechanical and cytocompatibility properties and can further be explored for potential biomedical applications.

Modulated in Vitro Biocompatibility of a Unique Cross-Linked Salicylic Acid-Poly(ε-caprolactone)-Based Biodegradable Polymer.

Herein, we report the development of a unique architecture by chemically cross-linking salicylic acid (SA)-based poly(anhydride ester) onto a biodegradable amine-functionalized poly(caprolactone) (PCL), using lactic acid as a spacer. The ester and amide linkages in the SA-PCL polymer, synthesized through melt condensation, were confirmed by NMR and FT-IR spectroscopic techniques. The enzymatic and nonenzymatic hydrolytic degradation profile exhibited linear degradation kinetics over an extended time period (>5 weeks). The compatibility and growth of C2C12 myoblast cells were found to be significantly improved on the fast-degrading SA-PCL substrates compared to those over neat PCL and amine-functionalized PCL. Further, the decreased red blood cell damage, illustrated by 0.39% hemolysis activity and a minimal number of platelet adhesion on a SA-PCL polymeric surface confirmed good hemocompatibility of the as-synthesized polymer. Together with a moderate bactericidal property, the spectrum of properties of this novel polymer can be attributed to the synergistic effect of the presence of chemical moieties of SA and amine groups in PCL. In summary, it is considered that a SA-PCL-based cross-linked composite can be utilized as a new biodegradable polymer.