In situ entrapment of urease in cryogels of poly(N‐isopropylacrylamide): An effective strategy for noncovalent immobilization of enzymes

Abstract

Supermacroporous poly(N-isopropylacrylamide) (PNIPAAm) cryogels containing urease were prepared via UV irradiation technique and hydrogen peroxide as initiator. Specifically, due to the cryostructuration phenomenon urease molecules were embedded into the dense cryogel walls. Thus, although the enzyme is physically entrapped, the system exhibited remarkable resistance against leaking due to the dense polymer network formed in the cryogel walls. The immobilized urease can catalyze the hydrolysis of urea in a broad temperature range in both batch and flow regime. The interconnected macropores assist for unhindered diffusion of the substrate and reaction products through the gel, thus, paving the way for consecutive reuse at a constant activity, in contrast to the conventional PNIPAAm hydrogel. Due to the spongy-like morphology PNIPAAm cryogels containing urease can be exploited as highly permeable membrane for direct removal of traces of urea from continuously flowing feed solutions.

A Brief History of Polymeric Cryogels

“…The efficiency of radiation-induced processes is mainly a function of the applied radiation dose but not of the temperature, as demonstrated in the pioneering studies conducted in Japan (see, e.g., [19,[93][94][95][96][97][98][99][100]). Yet another possibility for the preparation of cryogels of the polymerization type is the use of electron beams [101] or photoinitiation [102][103][104]. An essential point in this case is that the penetration capability of both these kinds of radiation is not very high, which limits the thickness of the samples.…”

Cryogels via UV Irradiation

“…Supermacroporous PNIPAAm cryogels containing urease were prepared via the UV irradiation technique, with hydrogen peroxide as initiator [34]. Taking the advantage of cryostructuration phenomenon during the cryogenic treatment, most enzyme molecules were embedded into the cryogel walls.…”

Biosurfactant Production by Pseudomonas aeruginosa BN10 Cells Entrapped in Cryogels

“…This method allows preparation of various biocompatible, biodegradable, and/or thermosensitive supermacroporous cryogels by irradiation of moderately frozen aqueous systems with UV light (irradiation dose rate of 950 J m -2 s -1 ) for 2 -5 minutes in the presence of a photoinitiator. Such materials have been exploited for immobilization of yeast cells (Velickova et al, 2010), bacteria capable to degrade xenobiotics (Satchanska et al, 2009;Topalova et al, 2011), fi broblast cells (Petrov et al, 2011a), enzymes (Petrov et al, 2011b(Petrov et al, , 2012, and drugs Kostova et al, 2011).…”