Polymeric hydrogels were used to create bio-smart hydrogels serving multifunctional roles interfacing with cells and enzyme substrates. Their value lies in their use as: i) Stimuli- responsive membranes that directly transmute chemical potential energy into proportionate electrical signals, ii) as biomimetically inspired biocompatible coatings on stents and other implantable bionic devices, iii) as bio receptor hosting membranes for enzyme-based implantable biosensors. Biosensors use oxidoreductase enzymes such as glucose oxidase (GOx) and lactate oxidase (LOx) to confer specificity. Such enzymes may initiate more complex in vivo inflammatory response. In this thesis individual and combined effects of different enzymes (GOx, Superoxide dismutase (SOD), and catalase) were studied to achieve hydrogelenzyme systems, which in theory may mitigate against adverse cell outcomes. The incorporation of enzymes into bioactive hydrogels was investigated, and revealed effects on the growth, viability and attachment of surface dependant RMS13 human muscle fibroblasts and B50 rat neuronal cells. Agarose and p(HEMA)-based hydrogels were prepared with fibrinogen 5% (w/v) to promote integrin-mediated cellular attachment and also with different combinations of glucose oxidase (GOx), catalase (CAT) and superoxide dismutase (SOD). Cell viability was maintained best on catalase hydrogels. The presence of GOx within hydrogels membrane compromised cell viability in both hydrogel types, presumably due to accumulation of H2O2 confirmed by amperometric detection using fabricated platinum needle electrodes. Hydrogels prepared with GOx and CAT showed improved cell viability, further suggesting the negative influence of H2O2. High temperature treatment of the enzyme-hydrogel membranes, resulting in enzyme denaturation, returned all constructs to control levels of viability, confirming the relationship of cell viability with enzyme activity. An additional study was undertaken into the viability and growth of B50 cells on crosslinked protein membranes of fibrinogen and albumin as a potential bioreactor surface. The use of crosslinked fibrinogen to facilitate cell growth within microfluidic channels appears to have been realized. Fabrication and use of miniaturized gold-filled silica recess and inlaid disc electrodes, compared with the use of agarose gels in the recesses was investigated to improve stabilization of an amperometric H2O2 electrode. From this, a microfluidic device with an integrated inner diameter working and counter / reference electrode was fabricated which showed feasibility of more rapid amperometric detection of H2O2 in miniature flow channels.

Thesis (M. Sc. (Microbiology)) -- University of Limpopo, 2016 / Smart hydrogels could facilitate immobilisation of cellulases to allow recovery and decrease enzyme cost in the biofuel industry, as they have a soluble-gel transition. The aim of the study was to design and evaluate the use of smart hydrogels for immobilisation of cellulase system that can be recovered after hydrolysis of cellulosic biomass. Cellulases from Aspergillus niger FGSC A733 produced under solid state fermentation and commercial cellulases were used in immobilisation. Various support matrices prepared were poly-N-isopropylacrylamide (p-NIPAAm), poly-N isopropylacrylamide-co-Methacrylic acid (p-NIPAAm-co-MAA) and supermacroporous poly-crosslinked-Acrylamide-co-N,N’-Methylenebisacrylamide (p-crosslinked-AA-co MBA). Cellulases were coupled onto the support matrices by covalent attachment method through reactive groups of N-acryloxysuccinimide (NAS) or Methacrylic acid N-hydroxysuccinimide (NMS). The low critical solution temperature (LCST) of formed p-NIPAAm-co-MAA copolymer was determined by the inflection point method. The shrinking and swelling kinetics and pH sensitivity of p-NIPAAm-co-MAA copolymer and conjugates were characterised using a cloud point method. Hydrolysis of CMC using cellulase-microbeads-p-NIPAAm and cellulase-crosslinked-p-NIPAAm with different percentage gel showed activity trend of 0.05>1>10>5>0.1% and 5>2>10% respectively. HPLC analysis showed that supplementation of β-glucosidase in cellulase-crosslinked-p-NIPAAm conjugates increased glucose by 12 and 14-fold at 30 and 50 °C respectively in the avicel hydrolysate in comparison with no β glucosidase supplementation. In the hydrolysis of avicel using cellulase-crosslinked p-NIPAAm-co-MAA conjugate a total of 13.6 g/L of reducing sugar was liberated after three cycles. In comparison a total of 21.4 g/L of reducing sugars were released from avicel hydrolysis using cellulase-crosslinked-p-AA-co-MBA conjugate after 3 cycles. In contrast, reducing sugars released in thatch grass hydrolysis using free enzyme were 8 times greater than in cellulase-crosslinked-p-AA-co-MBA conjugate. Cellulase crosslinked-p-NIPAAm-co-MAA conjugates were more stable than free enzyme at 50 and 60 °C after 24 hour and 120 minutes of incubation respectively, but lost activities at 65 °C after 120 minute. Therefore the activity loss in the immobilised enzymes was more due to thermal inactivation during precipitation and recovery than incomplete recovery during precipitation cycles. The results show that cellulases immobilised on smart polymers with sol-gel transition could be used in hydrolysis of cellulose due to ease of recovery. Hydrolysis kinetics was efficient for both immobilised enzyme system (cellulase-crosslinked-p-AA-co-MBA and cellulase-crosslinked-p-NIPAAm-co MAA conjugate) since were re-used in hydrolysis of avicel. Therefore the use of these smart polymers for cellulase immobilisation can contribute in cost reduction of the enzymatic hydrolysis process in the biofuel industry. / National Research Foundation (NRF) , University of Limpopo financial aid office and Flemish Interuniversity Council (VLIR-UOS) fo

Yes / Understanding the structure-property relationships of drug delivery system (DDS) components is critical for their development and the prediction of bodily performance. This study investigates the effects of introducing polyethylene oxide (PEO) homopolymers, over a wide range of molecular weights, into Pluronic injectable smart hydrogel formulations. These smart DDSs promise to enhance patient compliance, reduce adverse effects and dosing frequency. Pharmaceutically, Pluronic systems are attractive due to their unique sol-gel phase transition in the body, biocompatibility, safety and ease of injectability as solutions before transforming into gel matrices at body temperature. This paper presents a systematic and comprehensive evaluation of gelation and the interplay of microscopic and macroscopic properties under both equilibrium and non-equilibrium conditions in controlled environments, as measured by rheology in conjunction with time-resolved Small Angle Neutron Scattering (SANS). The non-equilibrium conditions investigated in this work offer a better understanding of the two polymeric systems’ complex interactions affecting the matrix thermo-rheological behaviour and structure and therefore the future release of an active pharmaceutical ingredient from the injectable DDS.