Manas Das

Novel magnetic antimicrobial nanocomposites for bone tissue engineering applications

In the present study, we demonstrate the fabrication of novel bone-like magnetic nanocomposites by the blending of chitosan, polymethylmethacrylate-co-2-hydroxyethylmethacrylate, and nano-hydroxyapatite–Fe3O4. The hybrid nanomaterials were thoroughly characterized by Fourier transform infrared spectroscopy, powder X-ray diffraction and field emission scanning electron microscopy. The magnetic nanocomposites exhibited excellent mechanical properties (e.g. tensile strength, Youngs modulus and stiffness) and antimicrobial activities. Hemolysis assays indicated that blood compatibility of the polymer sample is significant. Water uptake ability of the nanocomposite materials was found to increase with increasing the proportion of PMMA-co-PHEMA. In addition, the superparamagnetic nature of the nanocomposite was observed which makes these materials suitable for magnetic therapy.

Development of porous and antimicrobial CTS–PEG–HAP–ZnO nano-composites for bone tissue engineering

Herein, we have developed hybrid nanocomposites of chitosan, poly(ethylene glycol) and nano-hydroxyapatite–zinc oxide with interconnected macroporous structures for bone tissue engineering. These nanocomposites were characterized using different spectroscopic and analytical techniques. The percentage of porosity and the tensile strength of these materials were found to be similar to that of human cancellous bone. Moreover, these hybrid materials exhibited bio-degradability, a neutral pH (7.4) and erythrocyte compatibility. The addition of nano-hydroxyapatite–zinc oxide into the nanocomposites increased the antimicrobial activity and protein adsorption ability. The water uptake ability was found to increase with increasing the proportion of poly(ethylene glycol). Finally, osteoblast-like MG-63 cells were grown, attached and proliferated with these nanocomposites without them having any negative effect and the nanocomposites showed good cytocompatibility.

Development of bone-like zirconium oxide nanoceramic modified chitosan based porous nanocomposites for biomedical application.

Here, zirconium oxide nanoparticles (ZrO2 NPs) were incorporated for the first time in organic-inorganic hybrid composites containing chitosan, poly(ethylene glycol) and nano-hydroxypatite (CS-PEG-HA) to develop bone-like nanocomposites for bone tissue engineering application. These nanocomposites were characterized by FT-IR, XRD, TEM combined with SAED. SEM images and porosity measurements revealed highly porous structure having pore size of less than 1μm to 10μm. Enhanced water absorption capacity and mechanical strengths were obtained compared to previously reported CS-PEG-HA composite after addition of 0.1-0.3wt% of ZrO2 NPs into these nanocomposites. The mechanical strengths and porosities were similar to that of human spongy bone. Strong antimicrobial effects against gram-negative and gram-positive bacterial strains were also observed. Along with getting low alkalinity pH (7.4) values, similar to the pH of human plasma, hemocompatibility and cytocompatibility with osteoblastic MG-63 cells were also established for these nanocomposites. Addition of 15wt% HA-ZrO2 (having 0.3wt% ZrO2 NPs) into CS-PEG (55:30wt%) composite resulted in greatest mechanical strength, porosity, antimicrobial property and cytocompatibility along with suitable water absorption capacity and compatibility with human pH and blood. Thus, this nanocomposite could serve as a potential candidate to be used for bone tissue engineering.

Development of biomimetic nanocomposites as bone extracellular matrix for human osteoblastic cells.

Here, we have developed biomimetic nanocomposites containing chitosan, poly(vinyl alcohol) and nano-hydroxyapatite-zinc oxide as bone extracellular matrix for human osteoblastic cells and characterized by Fourier transform infrared spectroscopy, powder X-ray diffraction. Scanning electron microscopy images revealed interconnected macroporous structures. Moreover, in this study, the problem related to fabricating a porous composite with good mechanical strength has been resolved by incorporating 5wt% of nano-hydroxyapatite-zinc oxide into chitosan-poly(vinyl alcohol) matrix; the present composite showed high tensile strength (20.25MPa) while maintaining appreciable porosity (65.25%). These values are similar to human cancellous bone. These nanocomposites also showed superior water uptake, antimicrobial and biodegradable properties than the previously reported results. Compatibility with human blood and pH was observed, indicating nontoxicity of these materials to the human body. Moreover, proliferation of osteoblastic MG-63 cells onto the nanocomposites was also observed without having any negative effect.

Organically modified clay supported chitosan/hydroxyapatite-zinc oxide nanocomposites with enhanced mechanical and biological properties for the application in bone tissue engineering

The objective of this study is to design biomimetic organically modified montmorillonite clay (OMMT) supported chitosan/hydroxyapatite-zinc oxide (CTS/HAP-ZnO) nanocomposites (ZnCMH I-III) with improved mechanical and biological properties compared to previously reported CTS/OMMT/HAP composite. Fourier transform infrared spectroscopy, powder X-ray diffraction, scanning electron microscopy and transmission electron microscopy were used to analyze the composition and surface morphology of the prepared nanocomposites. Strong antibacterial properties against both Gram-positive and Gram-negative bacterial strains were established for ZnCMH I-III. pH and blood compatibility study revealed that ZnCMH I-III should be nontoxic to the human body. Cytocompatibility of these nanocomposites with human osteoblastic MG-63 cells was also established. Experimental findings suggest that addition of 5wt% of OMMT into CTS/HAP-ZnO (ZnCMH I) gives the best mechanical strength and water absorption capacity. Addition of 0.1wt% of ZnO nanoparticles into CTS-OMMT-HAP significantly enhanced the tensile strengths of ZnCMH I-III compared to previously reported CTS-OMMT-HAP composite. In absence of OMMT, control sample (ZnCH) also showed reduced tensile strength, antibacterial effect and cytocompatibility with osteoblastic cell compared to ZnCMH I. Considering all of the above-mentioned studies, it can be proposed that ZnCMH I nanocomposite has a great potential to be applied in bone tissue engineering.

Fabrication of porous magnetic nanocomposites for bone tissue engineering

Here, the fabrication and characterization of porous magnetic nanocomposites was carried out via the blending of chitosan, polyethylene glycol and nano-hydroxyapatite–Fe3O4. Scanning electron microscope images revealed a highly interconnected macro- and micro-porous structure. These nanocomposites showed good water uptake abilities and have good antimicrobial properties. The tensile strengths of these nanocomposites were enhanced significantly compared to previously reported results, after the addition of nano-Fe3O4. Moreover, these nanocomposites could be applied for magnetic therapy as this material exhibited superparamagnetic properties. Finally, these nanocomposites were good supports for human osteoblast-like MG-63 cells’ growth, attachment and proliferation and they showed good cytocompatibility. No negative effect on the MG-63 cells was observed, suggesting that these nanocomposites have great potential to be applied for bone regeneration.

Mechanical and biological investigations of chitosan–polyvinyl alcohol based ZrO2 doped porous hybrid composites for bone tissue engineering applications

ZrO2 nanoparticle (NP) doped CTS–PVA–HAP composites (ZrCPH I–III) were developed and characterized by FT-IR and XRD studies to mimic human bone for bone tissue engineering applications. Interconnected porous structures of these composites were observed via SEM and the porosities were in the range of human cancellous bone. These composites also have good swelling abilities both in aqueous and SBF media. The addition of ZrO2 NPs into the CTS–PVA–HAP composites improved the tensile strength of ZrCPH I–III compared with previously reported CTS–PVA–HAP composites, and the maximum tensile strength was obtained with ZrCPH III (CTS : PVA : HAP-ZrO2 = 55 : 30 : 15 wt%), which had the highest ZrO2 content (0.3 wt%). The strongest antimicrobial effect was also observed for ZrCPH III, which had the maximum amount of nano-HAP-ZrO2. Cytocompatibility with human osteoblastic MG-63 cells was also established and the highest cell proliferation was observed with ZrCPH III. Thus, ZrCPH III should have the potential to be applied as a bone tissue engineering material.

Bioethanol Fermentation from Untreated and Pretreated Bagasse Using Fusarium oxysporum

Abstract Comparisons were studied for untreated and pretreated bagasse with dilute alkaline peroxide and steam for bioethanol production by simultaneous saccharification and fermentation (SSF) process in a continuous stirred batch bioreactor using fungi Fusarium oxysporum. The optimum parameters for bioethanol fermentation were: time, 48 h; pH, 6.0; temperature, 50°C; stirring speed, 35 rpm; and bagasse loading, 35 g/L. Maximum concentrations of bioethanol at optimum fermentation process parameters were 18.73 g/L, 19.69 g/L and 20.45 g/L for untreated, steam and dilute alkaline peroxide pretreated bagasse, respectively. Maximum yields of bioethanol were 0.706 g/g, 0.734 g/g and 0.764 g/g of bagasse at optimum parameters for untreated, steam and dilute alkaline peroxide pretreated bagasse, respectively. The sp. growth rate (µ) of fungi Fusarium oxysporum was determined at 5.91 s−1, 6.25 s−1 and 7.11 s−1 and maximum sp. growth rate (µmax) was calculated at 11.81 s−1, 12.50 s−1 and 14.22 s−1 for untreated, steam and dilute alkaline peroxide pretreated bagasse, respectively. The sp. enzyme activity (ν) was found at 138a0 min−1, 1565 min−1 and 1695 min−1 and maximum sp. activity (νmax) was calculated at 2760 min−1, 3130 min−1 and 3390 min−1 for untreated, steam and dilute alkaline peroxide pretreated bagasse, respectively. The first order rate constants (k) were determined as 0.12 h−1, 0.14 h−1 and 0.156 h−1 for untreated, steam and dilute alkaline peroxide pretreated bagasse for fermentation in continuous stirred batch bioreactor, respectively.

Biomethanation of Distillery Wastewaters in Fluidised-Bed Bioreactor and Mathematical Modelling

Abstract An anaerobic three-phase fluidised-bed reactor (FBR) was used to treat distillery wastewaters for biogas generation using actively digested aerobic sludge from a sewage plant. The optimum digestion time was 8 h and optimum initial pH of feed was 7.5. The optimum temperature of feed was 40°C, optimum feed flow was 14 L/min and maximum organic loading rate (OLR) was 39.513 kg COD m−3 h−1. The OLRs were calculated on the basis of chemical oxygen demand (COD) inlet in the bioreactor at different flow rates. The maximum methane (CH4) concentration was 63.56% (v/v) of the total biogas generation at optimum biomethanation process parameters. The maximum biogas yield rate was 0.835 m3/kg COD m−3 h−1 with maximum CH4 yield rate (63.56% v/v) of 0.530 m3/kg COD m−3 h−1 at optimum digestion parameters. The maximum COD and biological oxygen demand (BOD) reduction of the distillery wastewaters were 76.82% (w/w) and 81.65% (w/w), respectively, with maximum OLR of 39.513 kg COD m−3 h−1 at optimum conditions. The optimisation of these parameters enabled stable functioning of the process and allowed the application of high loading rates. This study deals with mathematical modelling of the experimental data on biomethanation and suggests model equations relating kinetic parameter (rate constant k) and maximum specific growth rate μmax with respect to COD (substrate) removal. The mathematical modelling is also analysed for hydrodynamic pressure δp vs. feed flow u and hydrodynamic pressure δp with respect to CH4 gas yields.