Fabrication and Evaluation of Filtration Membranes from Industrial Polymer Waste.

Polyvinylidene fluoride (PVDF) polymers are known for their diverse range of industrial applications and are considered important raw materials for membrane manufacturing. In view of circularity and resource efficiency, the present work mainly deals with the reusability of waste polymer 'gels' produced during the manufacturing of PVDF membranes. Herein, solidified PVDF gels were first prepared from polymer solutions as model waste gels, which were then subsequently used to prepare membranes via the phase inversion process. The structural analysis of fabricated membranes confirmed the retention of molecular integrity even after reprocessing, whereas the morphological analysis showed a symmetric bi-continuous porous structure. The filtration performance of membranes fabricated from waste gels was studied in a crossflow assembly. The results demonstrate the feasibility of gel-derived membranes as potential microfiltration membranes exhibiting a pure water flux of 478 LMH with a mean pore size of ~0.2 µm. To further evaluate industrial applicability, the performance of the membranes was tested in the clarification of industrial wastewater, and the membranes showed good recyclability with about 52% flux recovery. The performance of gel-derived membranes thus demonstrates the recycling of waste polymer gels for improving the sustainability of membrane fabrication processes.

Effect of cellulose nanocrystals on chitosan/PVA/nano ß-TCP composite scaffold for bone tissue engineering application.

The need for an ideal tissue construct has lead to the search of a myriad of polymer composites with desirable properties. The nature, location and type of tissue to be regenerated determines the type of material to be used. A bone construct has its own requirements such as osteoconductivity, mineralization tendency, synchronized degradation rate, osteogenic differentiation potential etc, which results in search of new possible combination of materials aimed to improve tissue response. The present study involves fabrication of Chitosan/Polyvinyl alcohol (PVA)/ß-Tricalcium Phosphate (ß-TCP)/Cellulose nanocrystals (CNC) porous composite by freeze drying process to be used as bone tissue engineering matrix. CNCs were isolated by acid hydrolysis of cellulose derived from pistachio shells. The prepared scaffold samples were characterized by Fourier-transform infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and X-RAY Diffraction analysis (XRD). The scaffolds exhibited refinement in pore morphology and increased mineralization tendency on increasing CNC concentration. Samples with 1% and 5% CNC concentration have deposited apatite crystals with Ca/P ratio of 1.61 and 1.66 which is very close to the stoichiometric ratio of natural bone apatite. Compressive modulus of CS/PVA/ß-TCP/CNC composite increased on increasing the CNC concentration to 5%. The highest cell viability was recorded in scaffolds with 5% CNC content. Though cell attachment tendency was observed in all samples but the samples with 5 and 10% CNC content demonstrated higher cell densities with significant calcium depositions when cultured for 72 h. Samples with 5% CNC concentration also possessed highest cell differentiation capabilities.

Effect of incorporation of montmorillonite on Xylan/Chitosan conjugate scaffold.

The present study reports the fabrication of Xylan/Chitosan/Montmorillonite (MMT) composite scaffold by freeze drying process with the aim of achieving improved properties for bone tissue engineering applications. The scaffolds were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Scanning electron microscopy (SEM) and mechanical testing. The fabricated scaffolds were found to be highly porous with variations in pore size (102 µm-290 µm) on varying the filler concentration. XRD study revealed complete exfoliation of MMT incorporated in polymer conjugates (Xylan/Chitosan) prepared by Maillard reaction. In-vitro bio-mineralization study revealed significant apatite deposition on polymer matrix. Scaffolds with 5% MMT concentration exhibited needle like morphology of deposited apatite which can further provide synergistic response in increasing the mechanical properties of scaffolds when placed in contact with body fluid. The average length and thickness of apatite needles were calculated to be 140 µm and 1.2 µm respectively. The deposited apatite crystals on scaffold with 2% MMT content demonstrated Ca/P ratio of 1.67, resembling that of natural bone apatite. Swelling and biodegradation behavior of scaffold were also studied with regard to hydrophilic and barrier effect of MMT on composites. MTT assay revealed non-cytotoxic nature of scaffold with good cell viability.

Lipophilic 5-fluorouracil prodrug encapsulated xylan-stearic acid conjugates nanoparticles for colon cancer therapy.

In this study, self-assembled nanoparticles based on amphiphilic xylan-stearic acid (Xyl-SA) conjugates have been developed for the efficient delivery of 5-fluorouracil (5-FU) in cancer therapy. The self-assembled behavior of Xyl-SA conjugates in aqueous medium was investigated using pyrene as fluorescent probe. To enhance the loading efficacy of 5-FU, the lipophilic 5-fluorouracil-stearic acid (5-FUSA) prodrug was synthesized and subsequently encapsulated into the hydrophobic core of Xyl-SA NPs. The obtained Xyl-SA/5-FUSA NPs had an appropriate size (~278 nm), high drug loading of 5-FUSA (~14.6 wt%) and high physiological stability. The interaction of the Xyl-SA/5-FUSA NPs with blood components was investigated by hemolysis study. The cell cytotoxic studies demonstrated that Xyl-SA/5-FUSA NPs induced higher cytotoxicity than free drugs against the Human colorectal cancer cells (HT-29, HCT-15). These results indicate that Xyl-SA/5-FUSA NPs can serve as a promising drug delivery system for the efficient delivery of 5-FU in cancer therapy.

Studies on cellulose nanocrystals isolated from groundnut shells.

Today, various renewable biomass resources are accepted as waste material and are mostly burnt or used as cattle feed. The commercial value of these wastes can be increased by utilising them in production of nanomaterials. So, the present work was conducted for isolation of cellulose nanocrystals (CNCs) from groundnut shells which are produced annually as waste in large quantity (∼7 million tons). The structural, thermal, morphological & elemental analyses were assessed through corresponding techniques. Light Scattering studies were performed to analyse more likely weight average molecular weight (Mw) & radius of radius (Rg). The high Mw ∼105g/mol obtained for CNCs in lithium chloride (LiCl)/N,N-dimethylacetamide (DMAc) system, was an interesting feature which gets affected by LiCl and polymer concentrations. Solution with high polymer and low LiCl concentration was found to show higher values of Mw & Rg.