Water Uptake Of Hydrogels Research Articles

Effect of different polysaccharides on swelling of composite whey protein hydrogels: A low field (LF) NMR relaxometry study

AbstractHydrogels are usually prepared from hydrophilic polymers and when different types of polymers are blended or emulsified with an oil phase the resulting gel is usually known as a composite gel. The objective of this study was to analyze the water uptake characteristics of whey protein‐polysaccharide containing composite hydrogels. Composite and composite emulsion gels were formulated in this study using whey protein, xanthan (XN), pectin (PC), alginate (AL), and sunflower oil. Water absorption of hydrogels was studied using Nuclear Magnetic Resonance (NMR) relaxometry through transverse relaxation time (T2) measurements, and Non‐Negative‐Least‐Square (NNLS) analysis. Swelling ratios (SR) of different gels were determined. Swelling of the gels was also evaluated mathematically and water uptake of hydrogels was explained by the power law model and diffusion rate constants based on power law model were determined. Results showed that NMR relaxometry could be used to differentiate water uptake mechanisms of composite hydrogels.Practical applicationsBiodegradable hydrogels provide controlled delivery of nutrients, bioactive agents such as antioxidants and antimicrobial agents at a desired site and time and at a specific rate. Incorporating bioactive agents to these gels also protects sensitive nutrients and may increase the shelf life of some potential food products. The swelling characteristics of hydrogels provide information about the possible release behavior of the hydrogels. When a hydrogel is loaded with an agent and placed in an aqueous medium, usually the release rate of the agent from the gel and the swelling ratio (SR) of the gel due to solvent uptake from the surrounding medium is proportional to each other. In this study, effects of different polysaccharides on the SR of composite whey protein hydrogels were determined by NMR relaxometry. NMR enabled fast and easy monitoring for hydrogel swelling. Furthermore, NMR provided more detailed information on swelling mechanism than conventional methods proving potential for further applications.

Fabrication of Lomustine Loaded Chitosan Nanoparticles by Spray Drying and in Vitro Cytostatic Activity on Human Lung Cancer Cell Line L132

This study was aimed to develop lomustine loaded chitosan nanoparticles using a homogenization and spray drying technique. Effect of crosslinking agents (sodium tripolyphosphate (TPP), and sodium hexametaphosphate (HMP)) were studied on the leaching of drug, water uptake of hydrogels, drug release from matrix and its mechanism. N anoparticles were obtained in the average size range of 111±16.2 to 942±11.7 nm with polydispersity index (PDI) from 0.116±0.039 to 0.517±0.037. Zeta potential of nanoparticles was ranged from 29.0±1.1 to 56.0±1.1 mV. The % encapsulation ef fi ciency of nanoparticles ranged between 58±0.88% and 96±0.51%.nanoparticles were coated with PEG 6000 to modulate drug release. Swelling index of chitosan-TPP and chitosan-TPP-PEG nanoparticles was about 428% and 350% over the 4 h and it was more (about 465% and 395%) for chitosan-HMP and chitosan-HMP-PEG nanoparticles. Drug release was sustained and diffusion controlled. Optimized formulation was tested for anticancer activity and drug retention study. Cytotoxicity on human lung cancer cell line L132 was studied by trypan blue dye exclusion test. Drug loaded nanoparticles killed L132 cells more ef fi ciently than the corresponding drug alone (p< 0.05). Due to the increased surface area lomustine loaded TPP and HMP crosslinked chitosan nanoparticles showed better anticancer activity.

Swelling studies of super water retainer acrylamide/crotonic acid hydrogels crosslinked by trimethylolpropane triacrylate and 1,4-butanediol dimethacrylate

Superswelling acrylamide/crotonic acid (AAm/CA) hydrogels were prepared by free radical polymerization in aqueous solution of acrylamide (AAm) with crotonic acid (CA) as comonomer. For each copolymerization, four different composition of CA and a concentration of multifunctional crosslinkers such as trimethylolpropane triacrylate (TMPTA) and 1,4-butanediol dimethacrylate (BDMA) were used. As a result of dynamic swelling tests, the influence of the crosslinkers and the relative content of CA on the swelling properties were examined. AAm/CA hydrogels were swelled in the range of 1520-2980% in water, while AAm hydrogels swelled as 780 and 1360%. Equilibrium water content of AAm/CA hydrogels was calculated in the range of 88.73 and 96.75%. Water uptake of hydrogels was followed non-Fickian type diffusion.

Structural change and swelling mechanism of pH-sensitive hydrogels based on chitosan andD,L-lactic acid

Graft copolymerization of D,L-lactic acid (LA) onto chitosan (CS) was attempted without using a catalyst. pH-sensitive hydrogels were obtained which are based on two different components: a natural polymer and a synthetic polymer. These polyester substituents provide the basis for hydrophobic interactions that contribute to the formation of hydrogels. The swelling mechanisms in enzyme-free simulated gastric fluid (SGF, pH 2.2) or simulated intestinal fluid (SIF, pH 7.4) at 37°C were investigated. Meanwhile, structural changes of the graft copolymers in the different pH buffers were studied by FTIR, and these are discussed together with the swelling mechanisms. The effect of pH on the water uptake of hydrogel was investigated by using McIlvaine buffer with the same ionic strength. The morphological change of hydrogels in different aqueous solutions is investigated by scanning electron microscopy (SEM). © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3186–3192, 1999