Research Article Biopolymeric Formulations for Biocatalysis and Biomedical Applications Magdy M. M. Elnashar 1,2 and Tarek Kahil 3 1 Center of Excellence, Encapsulation & Nanobiotechnology Group, Polymers Department, National Research Center, El-Behouth Street, Cairo 12311, Egypt 2 Biochemistry Department, Medical School, Taif University, Hawyia, Taif 5700, Saudi Arabia 3 Microbial Chemistry Department, National Research Center, El-Behouth Street, Cairo 12311, Egypt Correspondence should be addressed to Magdy M. M. Elnashar; magmel@gmail.com Received 25 February 2014; Revised 14 May 2014; Accepted 15 May 2014; Published 17 June 2014 Academic Editor: Changyang Gong Copyright © 2014 M. M. M. Elnashar and T. Kahil. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Tree gel disks formulations prepared using chitosan (Chito) or polyethylenimine (PEI) followed by glutaraldehyde were prepared for biocatalysis and biomedical applications. Te carriers have been used to immobilize lactase covalently and it was evaluated in terms of enzyme loading capacity and enzyme kinetics (km and Vmax). Te Km of the Chito formulation was almost half that of the PEI formulations, which is favored in industries. On the other hand, the gel disks were evaluated in terms of their swelling kinetics and the gels’ morphology using SEM. Te mechanism of the three gels’ swelling was also studied and it was found to be non-Fickian, where the mechanism of transport depends on both the difusion and polymer relaxation, which are controlling the overall rate of water uptake. Te Chito formulation was 2–5 folds and PEI formulations were 33–62 folds in terms of the swelling rate constant and the difusion rate, respectively. Tese results were highly supported by the SEM. Tis study will help scientists to design the right polymer network for enzymes immobilization as well as control the surface area and the swelling power of the polymers for diferent applications such as drug delivery systems and tissue engineering. 1. Introduction Hydrogel is a network of polymer chains that are hydrophilic and is sometimes found as a colloidal gel in which water is the dispersion medium. Anionic and cationic hydrogels are networked structures of polymer chains cross-linked to each other and surrounded by an aqueous solution [1, 2]. Te polymer chains contain acidic groups (anionic) which deprotonate at high pH leaving a negative charge on the polymer; for example, carrageenan gel as an anionic polymer contains –OH and –OSO 3 H groups; in an acidic medium, it deprotonates, where the –OH and –OSO 3 H groups become –O − and –OSO 3 − , respectively. On the other hand, the basic groups (cationic) protonate at low pH leaving a posi- tive charge; for example, chitosan and polyethylenimine as cationic polymers contain –NH 2 groups; in acidic medium, they protonate to –NH 3 + . In the presence of an aqueous solution, the polymer chains absorb water and the associ- ation, dissociation, and binding of various ions to polymer chains cause the hydrogel to swell. Te swelling and shrinking properties of hydrogels are currently being exploited in a number of applications including control of microfuidic fow [3], muscle-like actuators [4, 5], fltration/separation [6], and drug delivery systems [7, 8]. Common uses for hydrogels include also scafolds in tissue engineering; hydrogel-coated wells have been used for cell culture, environmentally sensitive hydrogels which are also known as “smart gels” or “intelligent gels,” as sustained- release drug delivery systems, and as biosensors, used in dis- posable diapers where they absorb urine, in sanitary napkins, in contact lenses (silicone hydrogels, polyacrylamides), in EEG and ECG medical electrodes using hydrogels composed of cross-linked polymers (polyethylene oxide, polyAMPS, Hindawi Publishing Corporation BioMed Research International Volume 2014, Article ID 418097, 10 pages http://dx.doi.org/10.1155/2014/418097