In vivo oxalate degradation by liposome encapsulated oxalate oxidase in rat model of hyperoxaluria.

BACKGROUND & OBJECTIVES: High level of urinary oxalate substantially increases the risk of hyperoxaluria, a significant risk factor for urolithiasis. The primary goal of this study was to reduce urinary oxalate excretion employing liposome encapsulated oxalate oxidase in animal model. METHODS: A membrane bound oxalate oxidase was purified from Bougainvillea leaves. The enzyme in its native form was less effective at the physiological pH of the recipient animal. To increase its functional viability, the enzyme was immobilized on to ethylene maleic anhydride (EMA). Rats were injected with liposome encapsulated EMA- oxalate oxidase and the effect was observed on degradation of oxalic acid. RESULTS: The enzyme was purified to apparent homogeneity with 60-fold purification and 31 per cent yield. The optimum pH of EMA-derivative enzyme was 6.0 and it showed 70 per cent of its optimal activity at pH 7.0. The EMA-bound enzyme encapsulated into liposome showed greater oxalate degradation in 15 per cent casein vitamin B 6 deficient fed rats as compared with 30 per cent casein vitamin B 6 deficient fed rats and control rats. INTERPRETATION & CONCLUSIONS: EMA-oxalate oxidase encapsulated liposome caused oxalate degradation in experimental hyperoxaluria indicating that the enzyme could be used as a therapeutic agent in hyperoxaluria leading to urinary stones.

Development of an amperometric sulfite biosensor based on a gold nanoparticles/chitosan/multiwalled carbon nanotubes/polyaniline-modified gold electrode.

A sulfite oxidase (SOx) purified from leaves of Syzygium cumini (Jamun) was immobilized covalently onto a gold nanoparticles (AuNPs)/chitosan (CHIT)/carboxylated multiwalled carbon nanotubes (cMWCNTs)/polyaniline (PANI) composite that was electrodeposited onto the surface of a gold (Au) electrode. A novel and highly sensitive sulfite biosensor was developed that used this enzyme electrode (SOx/AuNPs/CHIT/cMWCNT/PANI/Au) as the working electrode, Ag/AgCl as the standard electrode, and Pt wire as the auxiliary electrode. The modified electrode was characterized by Fourier transform infrared (FTIR) spectroscopy, cyclic voltammetry (CV), scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS) before and after the immobilization of the SOx. The sensor produced its optimum response within 3 s when operated at 50 mVs(-1) in 0.1 M phosphate buffer, pH 7.0, and at 35 °C. The linear range and detection limit of the sensor were 0.75-400 µM and 0.5 µM (S/N = 3), respectively. The biosensor was employed to determine sulfite levels in fruit juices and alcoholic beverages. The enzyme electrode was used 300 times over a period of three months when stored at 4 °C.

Lab on paper chip integrated with Si@GNRs for electroanalysis of diazepam.

We describe herein the fabrication of an electrochemical microfluidic paper based device (EµPAD) for the detection of diazepam, a sedative, anxiety-relieving and muscle-relaxing drug. To achieve it, silica coated gold nanorods (Si@GNRs) were synthesized and drop casted on an electrochemical microfluidic paper based device (EµPAD) for the detection of diazepam. The synthesized composites were characterized by recording its images in scanning electron microscope (SEM) and transmission electron microscope (TEM). The experimental results confirmed that Si@GNRs had good electrocatalytic activity towards diazepam. The modified paper based electrode showed a stable electrochemical response for diazepam in the concentration range of 3.5 nM to 3.5 mM. EµPAD offers many advantageous features such as facile approach, economical and have potential for commercialization. Si@GNRs modified EµPAD was also employed for determination of diazepam in spiked human urine samples. Reported facile lab paper approach integrated with Si@GNRs could be well applied for the determination of serum metabolites.

Construction of amperometric uric acid biosensor based on uricase immobilized on PBNPs/cMWCNT/PANI/Au composite.

A chitosan-glutaraldehyde crosslinked uricase was immobilized onto Prussian blue nanoparticles (PBNPs) absorbed onto carboxylated multiwalled carbon nanotube (c-MWCNT) and polyaniline (PANI) layer, electrochemically deposited on the surface of Au electrode. The nanohybrid-uricase electrode was characterized by scanning electron microscopic (SEM), Fourier transform infrared spectroscopy (FTIR) and cyclic voltammetry. An amperometric uric acid biosensor was fabricated using uricase/c-MWCNT/PBNPs/Au electrode as working electrode, Ag/AgCl as standard and Pt wire as auxiliary electrode connected through a potentiostat. The biosensor showed optimum response within 4s at pH 7.5 and 40°C, when operated at 0.4V vs. Ag/AgCl. The linear working range for uric acid was 0.005-0.8 mM, with a detection limit of 5 µM. The sensor was evaluated with 96% recovery of added uric acid in sera and 4.6 and 5.4% within and between batch of coefficient of variation respectively and a good correlation (r=0.99) with standard enzymic colorimetric method. This sensor measured uric acid in real serum samples. The sensor lost only 37% of its initial activity after its 400 uses over a period of 7 months, when stored at 4°C.