Single Haemoglobin Nanocapsules as Test Materials for Artificial Blood

Abstract

Single protein nanocapsules (SPNs) Keywords single haemoglobin nanocapsules · artificial blood · biocompatibility · allergic reaction IntroductionProteins usually catalyze biological reactions and have enzymatic function. Enzymes are bioreactors with high specificity and selectivity. But enzymes have a great sensitivity and a relatively brief life-time [1]. The relatively short lifetime of enzymes and their sensibility to change in the environment (pH, temperature, mechanical stress, etc.) tends to limit their biotechnological application. The increase of the lifetime and stability of enzymes are crucial to widen usage of enzymes. Improvement in enzyme stability can reduce the amount of enzyme required, can extend the lifetime of enzymes and can increase the reuse of enzymes [2][3][4][5][6][7]. Enzyme immobilization to the surface or onto the inner cavities of greater structures with adsorption or covalent linkage is an effective strategy to increase its lifetime [2,3]. Covalent linkage between the enzyme molecule and carrier material can reduce the unfolding mechanism of ternary structure of enzyme molecule and increase the stability of enzyme [4]. During the last decade there is a growing interest in minimized-size enzyme carriers [8,9].Single enzyme nanocapsules (SEN), or single protein nanocapsules (SPN) mean that a single protein molecule is covered with a few nanometer thick polymer layer [10][11][12][13][14][15] (Figure 1: Structure). This spatial polymer layer is thin and porous and allows the diffusion of substrate molecules to the active centre of the enzyme. Single enzyme nanoparticles involve the advantages of the multi-point covalent attachment [4] and closing of molecules onto inner cavities [16]. This technique needs a special polymerization step: in situ polymerization starting from the previously modified surface of the protein molecules ("Grafting from" method The quaternary protein structures (e.g. tetrameric haemoglobin molecules), as a functional unit does not change during the preparation of the single protein nanocapsules, i.e. covering enzymes by a thin polymeric layer (Figure 1: Structure). It has been proved that single enzyme nanocapsules, using organic/inorganic hybrid layer [10,12,13,14] organic acrylic copolymer [11,15], hyperhranched polymer layer [18] or superparamagnetic layer [19,20], can essentially stabilize enzymes. 58(Sup), pp. 11-16, 2014 DOI:10.3311 The nano-capsule around the enzymes is multifunctional (Figure 1: Functions). Single protein nanocapsules have 1) stabilization function a) mechanical stability, when under mechanical stress (circular stirring) the single enzyme nanocapsules are more stable than natural enzymes (enzymes without nano-layer) [12,13,14]; b) heat stability: when at extremely high temperature (80°C) single enzyme nanocapsules have greater stability than natural enzymes [12,13,14]. c) pH-stability: at extremely acidic (pH = 1.5) or alkaline (pH = 12.0) pH-values the activity of single enzyme nanocapsules are not reduced essentially, whi...

Robust Single-Molecule Enzyme Nanocapsules for Biosensing with Significantly Improved Biosensor Stability

“…and possess short shelf life, which consequently limits their applications in different fields. , Any improvement in increasing enzyme stability and shelf life is very crucial to broadening their applications . Reportedly, encapsulating enzyme molecules within a permeable polymer shell significantly enhances their stability without compromising their bioactivity. Enzyme nanocapsules are composed of a protein molecule enclosed within a very thin permeable and porous polymer layer that allows easy diffusion of substrate molecules to the active center of the enzyme. , Literature reports synthesis and fabrication of organophosphorus hydrolase (OPH) enzyme nanocapsules for detoxification and decontamination of organophosphate contaminants .…”

“…1,2 Any improvement in increasing enzyme stability and shelf life is very crucial to broadening their applications. 3 Reportedly, encapsulating enzyme molecules within a permeable polymer shell significantly enhances their stability 4 without compromising their bioactivity. Enzyme nanocapsules are composed of a protein molecule enclosed within a very thin permeable and porous polymer layer that allows easy diffusion of substrate molecules to the active center of the enzyme.…”

Artificial Blood Substitutes: First Steps on the Long Route to Clinical Utility

“…2). 61 An oxygen carrier has been developed by a research group, in which Hb is conjugated to biodegradable polymer micelles. 17 The micelle is a PEG-PMPC-PLA triblock copolymer in which PEG acts as shell, PMPC (PLA-b-poly (2-methacryloyloxyethyl phosphorylcholine)) bearing propargyl groups as the middle layer and PLA as core layer.…”

Biomedical Applications of Single Protein Nanoparticles

“…Furthermore, responsive polymer layers can releases its protein cargoes in the cell under specific local intracellular conditions or events, e.g., (1) at low pH values in endosomes (pH~5.5) [34] or (2) enzyme digestion [35]. The biocompatibility of haemoglobin nanocapsules covered by acrylamide-bisacrylamide random copolymer was investigated and good values were detected [36]. These results suggest immune isolation function of the polymer nanolayer but further investigations are needed.…”