Guar-Based Injectable Thermoresponsive Hydrogel as a Scaffold for Bone Cell Growth and Controlled Drug Delivery.

In this study, an injectable thermoresponsive hydroxypropyl guar-graft-poly(N-vinylcaprolactam) (HPG-g-PNVCL) copolymer was synthesized by graft polymerization. The reaction parameters such as temperature, time, monomer, and initiator concentrations were varied. In addition, the HPG-g-PNVCL copolymer was modified with nano-hydroxyapatite (n-HA) by in situ covalent cross-linking using divinyl sulfone (DVS) cross-linker to obtain HPG-g-PNVCL/n-HA/DVS composite material. Grafted copolymer and composite materials were characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis, proton nuclear magnetic resonance spectroscopy (1H NMR), and differential scanning calorimetry. The morphology of the grafted copolymer (HPG-g-PNVCL) and the composite (HPG-g-PNVCL/n-HA/DVS) was examined using scanning electron microscopy (SEM), which showed interconnected porous honeycomb-like structures. Using Ultraviolet-visible spectroscopy, low critical solution temperature for HPG-g-PNVCL was observed at 34 °C, which is close to the rheology gel point at 33.5 °C. The thermoreversibility of HPG-g-PNVCL was proved by rheological analysis. The HPG-g-PNVCL hydrogel was employed for slow release of the drug molecule. Ciprofloxacin, a commonly known antibiotic, was used for sustainable release from the HPG-g-PNVCL hydrogel as a function of time at 37 °C because of viscous nature and thermogelation of the copolymer. In vitro cytotoxicity study reveals that the HPG-g-PNVCL thermogelling polymer works as a biocompatible scaffold for osteoblastic cell growth. Additionally, in vitro biomineralization study of HPG-g-PNVCL/n-HA/DVS was conducted using a simulated body fluid, and apatite-like structure formation was observed by SEM.

Fabrication and characterization of hydroxypropyl guar-poly (vinyl alcohol)-nano hydroxyapatite composite hydrogels for bone tissue engineering.

Biocompatible bone implants composed of natural materials are highly desirable in orthopedic reconstruction procedures. In this study, novel and ecofriendly bionanocomposite hydrogels were synthesized using a blend of hydroxypropyl guar (HPG), poly vinyl alcohol (PVA), and nano-hydroxyapatite (n-HA) under freeze-thaw and mild reaction conditions. The hydrogel materials were characterized using various techniques. TGA studies indicate that both composites, HPG/PVA and HPG/PVA/n-HA, have higher thermal stability compared to HPG alone whereas HPG/PVA/n-HA shows higher stability compared to PVA alone. The HPG/PVA hydrogel shows porous morphology as revealed by the SEM, which is suitable for bone tissue regeneration. Additionally, the hydrogels were found to be transparent and flexible in nature. In vitro biomineralization study performed in simulated body fluid shows HPG/PVA/n-HA has an apatite like structure. The hydrogel materials were employed as extracellular matrices for biocompatibility studies. In vitro cell viability studies using mouse osteoblast MC3T3 cells were performed by MTT, Trypan blue exclusion, and ethidium bromide/acridine orange staining methods. The cell viability studies reveal that composite materials support cell growth and do not show any signs of cytotoxicity compared to pristine PVA. Osteoblastic activity was confirmed by an increased alkaline phosphatase enzyme activity in MC3T3 bone cells grown on composite hydrogel matrices.

Nanocrystalline Cellulose-Derived Doped Carbonaceous Material for Rapid Mineralization of Nitrophenols under Visible Light.

Nitrophenols (NPs) and related derivatives are industrially important chemicals, used notably to synthesize pharmaceuticals, insecticides, herbicides, and pesticides. However, NPs and their metabolites are highly toxic and mutagenic. They pose a serious threat to human health and ecosystem. Current work was undertaken to develop a suitable visible-light active catalyst for the sustainable and efficient mineralization of NPs in an aqueous environment. Nanocrystalline cellulose (NCs)-based nitrogen-doped titanium dioxide and carbonaceous material (N-TiO2/C) was synthesized by pyrolysis and sol-gel methods using NCs, polydopamine, and TiO2. The synthesized N-TiO2/C was characterized using different analytical techniques. Photocatalytic degradation of NPs under visible light indicated that acidic pH (3) was most suitable for the optimal degradation. 4-NP degradation followed both pseudo-first-order (R 2 = 0.9985) and Langmuir-Hinshelwood adsorption kinetic models (adsorption constant, K LH = 1.13 L mg-1). Gas chromatography-mass spectrometry and ion chromatography analysis confirmed the total mineralization of 4-NP into smaller molecular fragments such as acids, alcohols, and nitrates. The total organic carbon showed that 67% of total carbon present in 4-NP was mineralized into CO2 and CO. The catalyst was recycled for five consecutive cycles without losing its catalytic activities. The degradation mechanism of NPs with N-TiO2/C was also explored.