Artificial cells, blood substitutes, and immobilization biotechnology最新文献

Gastroretentive floating microspheres have a potential for enhancing the bioavailability and controlled delivery of drugs. The present study involves development of rifampicin floating microspheres in order to increase the gastric retention time. The microspheres were prepared by solvent evaporation technique and characterized for particle size, shape, zeta-potential, entrapment, and release kinetics. The developed systems were almost spherical in shape. The entrapment efficiency was found to be 86.34%. The percentage buoyancy after 8 hours was found to be 61.06. The prepared microspheres exhibited prolonged drug release in gastric medium and hence could be utilized for sustained delivery of anti-tubercular drugs.

β-galactosidase splits lactose into glucose and galactose. Because of its biotechnological interest, we presented a biosensor system in order to monitor β-galactosidase activity. Immobilization steps of the biosensor were identified by cyclic voltammograms and electrochemical impedance spectroscopy. β-galactosidase was voltammetrically detected at about +150 mV (vs. Ag/AgCl) in citrate buffer solution (0.05 M, pH 4.8). The linear response for β-galactosidase detection was in the range of 0.0118 U mL(-1)to 0.47 U mL(-1)and a shorter response time of ∼50 s. Our results demonstrated the biosensor's electrochemical properties and analytical characteristics were very useful and effective for monitoring of β-galactosidase activity.

A glucose oxidase-based biosensor was developed for the determination of α-amylase activity. The determination method is based on monitoring the decrease in dissolved oxygen concentration related to the starch concentration, for which starch gives a reaction with α-amylase. Optimization parameters, including glucose oxidase amount, gelatin amount, and glutaraldehyde percentage for cross-linking, were investigated. The effects of pH, buffer system, and temperature on the biosensor system were also investigated. The biosensor had a linear relation to α-amylase activity and good measurement correlation between 0.66 and 9.83 U/ml. In sample analysis studies, α-amylase activity in baker's yeast was determined by the biosensor.

Fibers comprised of reconstituted type I collagen were prepared by a gravity filament forming process and crosslinked with 0.1% glutaraldehyde. These fibers have a crosslinking index of about 90% (89.89 ± 1.82%) with higher denature temperature (74.43 ± 0.08°C) as compared to that without glutaraldehyde treatment (52.1 ± 0.17°C). The ultimate tensile strength of the collagen fibers increases from 99.4 ± 12.9 to 174.4 ± 9.0 MPa after glutaraldehyde-crosslinking. L929 fibroblast cells were seeded and cultured using these newly developed collagen fibers. The fibroblast cells proliferated well and covered all surface areas of the collagen fiber. These collagen fibers have a great potential for application in 3-D tissue engineering.

Herein, we describe a non-conventional method for immobilization of enzymes onto different solid surfaces using ultrasound as a source of energy. When horseradish peroxidase (HRP) was taken on the surface of an activated support and allowed to float on a sonicator bath operating at a frequency of 40 KHz, it readily started binding itself to the surface. Maximum binding was observed in 10 min whereas a control experiment carried out similarly without ultrasound waves showed insignificant immobilization. Ultrasound wave-mediated immobilization is rapid and reproducible and is better suitable for versatile applications in different fields, including fabrication of enzyme-based biosensors or bioreactors.

Abstract: An ascorbate oxidase purified from the green fruit of zucchini squash (Cucurbita pepo medullosa) was immobilized photochemically on a polyethylene disc with 85% retention of initial activity of free enzyme. The optimum pH (5.5) was unchanged, while K(m) was decreased. The polyethylene discs were employed for determination of ascorbic acid in serum and foodstuffs. The working linear range was 2.8 μM to 16 μM. The mean value of ascorbic acid in serum as measured by the method was 0.16 mg/dl in males and 0.209 mg/dl in females. The immobilized enzyme was used 100 times over 4 months, when stored at 4°C.

Alkaline phosphatase (ALP) was immobilized with cross-linking agents glutaraldehyde and cysteamine by forming a self-assembled monolayer on a screen printed gold electrode. ALP converts p-nitrophenyl phosphate to p-nitrophenol and phosphate. p-Nitrophenol loses H(+) ion and turns into the negatively charged compound p-nitrophenolate at medium pH. As a result, the unstable product formed is measured chronoamperometrically at an application potential of + 0.95 V. The biosensor response depends linearly on p-nitrophenyl phosphate concentration between 0.05 - 0.6 mM with a response time of 40 seconds. Detection limit of the biosensor is 0.033 mM.

Abstract: In this paper, a new viewpoint on the activity determination of β-galactosidase is reported. Glucose oxidase was directly immobilized on a glassy carbon electrode and mediated by ferrocene. The biosensor's performance was based on mediated electron transfer by ferrocene, which reduced via glucose oxidase reaction. In this reaction, substrate of glucose oxidase, glucose was provided by the activity of β-galactosidase in the sample. The parameters of the fabrication process for the electrode were optimized. Experimental conditions influencing the biosensor performance, such as pH, ferrocene and lactose concentrations, and temperature, were investigated and assessed. Finally, the biosensor was successfully applied to determination of β-galactosidase activity of artificial intestinal juice.

In this study, inkjet bio-printing has been used to produce miniaturized alginate microcapsules. A parametric study using subsequent Taguchi L(18) (3(1) × 2(7)) and L(16) (4(5)) designs was performed to elucidate the effect of inkjet parameters on microcapsule size. A 120-minute pilot run using the optimal waveform parameters and 0.5% alginate ink yielded a throughput of 1.8×10(6) microcapsules/hr, averaging 40 μm in diameter. Real-time stable jetting conditions were confirmed visually by the generation of a single droplet with a straight trajectory and non-fluctuating Ohnesorge numbers. The rate of stirring of the cross-linking CaCl(2) solution determined scaffold vs. single vesicle formation.

We have previously reported that derivatization of hemoglobin with periodate-modified sugar derivatives such as oxidized adenosine triphosphate (oATP) leads to an increase in prooxidant reactivity at the heme. Here, we report that copolymerization of hemoglobin with serum albumin alleviates this problem completely, to the extent where the copolymer even has a slightly lower autooxidation rate compared to native hemoglobin. A similar, although not as potent, effect is obtained when hemoglobin is derivatized with oATP in the presence of small-molecule antioxidants instead of albumin.