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Title: Hydrogel from seeds of Mimosa pudica L. isolation, modifiation, characterization and applications
Authors: Muhammad, Gulzar
Keywords: Chemistry
Issue Date: 2018
Publisher: University of Sargodha, Sargodha.
Abstract: A polysaccharide based hydrogel, i.e., glucuronoxylan (GX) was isolated from seeds of MP using hot water extraction method. The isolated Mimosa pudica hydrogel (MPH) was characterized and used for various formulation designs and stimuli responsive applications. Characterization of MPH was carried out using several spectroscopic, microscopic, degradative and chromatographic techniques, e.g., Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), powdered X-ray diffraction (PXRD) and thermogravimetric analysis (TGA). In order to modify the MPH, its acetylation was performed and structures obtained were thoroughly characterized which indicated that the polysaccharide under investigation can be modified easily to obtained tailored esters derivatives. Our interest was to modify this GX to prepare its succinylated derivatives potential for heavy metal ion uptake based on ion exchange mechanism. Moreover, we have also assessed pH and saline sensitive swelling behaviour of MPH along with its water holding potential and sustained drug release. MPH showed negligible swelling in hydrochloric acid buffer and enhanced swelling in phosphate buffers and deionized water. MPH deswells in salt solutions such as NaCl and KCl solutions, and ethanol. The swelling of MPH follows second order kinetics. Furthermore, MPH was found to be a sustained release material for diclofenac sodium tablet formulations. The drug release follows super case-II transport mechanism. It was noted that MPH is a potential candidate to develop intelligent drug delivery systems. The stimuli responsive properties and high water holding capability urged us to employ MPH as sustained release material for MPH-theophylline and MPH-levosulpiride tablet formulations and found that MPH delayed the release of above said dugs. MPH-theophylline and MPH-levosulpiride tablets were also analyzed for their stimuli responsive swelling 2 deswelling behaviour. The tablet formulations respond less to various stimuli than powder MPH due to close packing under compression. MPH appeared as promising material for delayed release of theophylline and levosulpiride. The presence of interconnected macropores with an average diameter of 62.94 µm was revealed using scanning electron microscopy (SEM) of a swollen then freeze dried sample of MPH. Similar pattern of macropores was also witnessed in tablets formed using MPH. High swelling index and water holding capability of MPH is obviously due to these microporous structures observed upon swelling then freeze drying. Keeping in view the role of polysaccharides in green synthesis of Ag NPs, we are reporting synthesis of silver nanoparticles based on GX polysaccharide present in MPH and their antimicrobial activity. GX isolated from seeds of Mimosa pudica was successfully used as a stabilizing and capping agent to prepare nanoparticles from different concentrations of AgNO3. The progress of reaction was monitored by UV-vis spectrophotometer and absorption bands were found in the range of 390-465 nm. Topography of the nanoparticles was observed by scanning electron microscopy. The synthesized nanoparticles exhibited significant antimicrobial activity against Staphylococcus epidermidis (ATCC 12228), Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC 27853), Bacillus subtilis (ATCC 6633), Staphylococcus aureus (ATCC 25923), Aspergilis niger, Penicillum notatum, Rhizopus and Actinomycetes. Wound healing studies revealed that Ag NPs prepared using GX could have potential applications as an antimicrobial dressing in wound management procedures. MPH based Ag NPs dressings appeared useful to prevent any infection to wounds in rabbit models and additionally it has promoted the wound healing procedure. MPH was also assessed for acute dermal toxicity and eye irritation in albino mice and rabbits. Three groups II, III and IV received GX at a dose of 1, 2 and 5 g/kg while group I was administered with routine diet. During two weeks study, it was concluded that there was 3 insignificant difference in body weight, behavioural pattern, and food and water intake among treated and control groups. Haematology and biochemistry of blood samples from all groups were found analogous. Histopathological evaluation of vital body organs of treated and control groups exhibited no lesions. Moreover, cardiac and ocular safety of GX was proven. Acquiring thermal data of any material is important to get information about its stability. Therefore, comparative thermal degradation and kinetics of MPH and its acetylated derivative (AMPH) were investigated at multiple heating rates (isoconversional method). Thermal data of MPH and AMPH was fitted to Flynn–Wall–Ozawa (FWO) and Kissinger methods, and energy of activation (Ea) was calculated. Two step exothermic degradation was observed from TG curves of both MPH and AMPH. The Ea values calculated by Kissinger and FWO models for first step of degradation of AMPH were found in the range of 105.41 108.49 kJ mol-1 which were comparable with Ea values of unmodified MPH. The mean values of integral procedural decomposition temperature (IPDT) for MPH and AMPH were found to be 338 °C and 346 °C, respectively. The mean comprehensive index of thermal stability (ITS) was found to be 0.55 for MPH and AMPH showing both materials much stable than many commercially available ingredients used in drug designing. Succinylated MPH (MPH-Suc) was evaluated for its metal sorption capacity in order to remove cadmium (Cd) from spiked high-hardness groundwater (GW) as well as from aqueous solution. MPH was esterified with succinic anhydride using dimethylaminopyridine as catalyst to fabricate succinylated MPH (MPH-Suc). MPH-Suc was converted into the sodium salt (MPH-Suc-Na). Effect of contact time (5-120 min) and pH (1-10) on Cd-uptake by the MPH-Suc-Na was thoroughly investigated. The supersorbent, MPH-Suc-Na showed more than 90% Cd-removal in first 5 and 15 min from distilled water (DW) and ground water (GW) solution, respectively. A careful comparison of sorption data of MPH-Suc-Na with 4 other polysaccharidal sorbents suggested its high efficiency (DW 145.5 and GW 140.5 mg/g) and selectivity for removal of Cd by an ion exchange mechanism. This ion exchange mechanism is further supported by the negative Gibbs free energy values. Sorption data of MPH-Suc-Na was fitted to different kinetic models, from which Langmuir isotherm kinetic model provided the best fit for the sorption of Cd. The sorbent MPH-Suc-Na appeared regenerable and can be reused over many cycles. The thermal stability testing of the sorbents indicated that MPH-Suc-Na (sorbent) is more stable than MPH-Suc.
Gov't Doc #: 19259
Appears in Collections:PhD Thesis of All Public / Private Sector Universities / DAIs.

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