Clay nanosheets simultaneously intercalated and stabilized by PEGylated chitosan as drug delivery vehicles for cancer chemotherapy.

Montmorillonite (MMT) has been frequently utilized as drug vehicles due to its high specific surface area, excellent cation exchange capacity and biocompatibility. However, the significant flocculation of MMT under physiological condition restricted its application to drug delivery. To conquer this problem, the graft-type PEGylated chitosan (PEG-CS) adducts were synthesized as intercalator to stabilize MMT dispersion. Through electrostatic attraction between the chitosan and MMT, the PEG-CS adducts were adsorbed on MMT surfaces and intercalated into MMT. The resulting PEG-CS/MMT nanosheets possessed PEG-rich surfaces, thus showing outstanding dispersion in serum-containing environment. Moreover, the physicochemical characterization revealed that the increased mass ratio of PEG-CS to MMT led to the microstructure transition of PEG-CS/MMT nanosheets from multilayered to exfoliated structure. Interestingly, the PEG-CS/MMT nanosheets with mass ratio of 8.0 in freeze-dried state exhibited a hierarchical lamellar structure organized by the intercalated MMT bundles and unintercalated PEG-CS domains. Notably, the multilayered PEG-CS/MMT nanosheets showed the capability of loading doxorubicin (DOX) superior to the exfoliated counterparts. Importantly, the DOX@PEG-CS/MMT nanosheets endocytosed by TRAMP-C1 cells liberated the drug progressively within acidic organelles, thereby eliciting cell apoptosis. This work provides a new strategy of achieving the controllable dispersion stability of MMT nanoclays towards application potentials in drug delivery.

Methylene blue-mediated photodynamic inactivation as a novel disinfectant of enterovirus 71.

OBJECTIVES: We tested whether methylene blue, an inexpensive and safe photosensitizer, is feasible for photodynamic inactivation of enterovirus 71 (EV71) in the environment. METHODS: By escalating light doses and photosensitizer concentrations, photoinactivation of EV71 and other enteroviruses was examined in vitro. Viral transmission in the environment was simulated with a neonatal mouse model in vivo. Possible mechanisms were analysed with alterations of viral DNA and proteins after treatments. RESULTS: Photodynamic inactivation of EV71 in suspensions occurred in a dose-dependent manner. The optimal condition for photoinactivating EV71 required a light dose of 200 J/cm(2) in the presence of methylene blue. This photodynamic condition was also able to inactivate other enteroviruses, including poliovirus 1 and coxsackieviruses A2, A3, A16 and B3. In an imitation environment, EV71 spread on a solid surface was inactivated by methylene blue-mediated photodynamic inactivation and prevented EV71 transmission to mice. Western blot and RT-PCR analysis indicated that both the viral proteins and the genome were disrupted after photodynamic inactivation. CONCLUSIONS: Methylene blue-mediated photodynamic inactivation may provide a novel way to eliminate environmentally contaminated sources of EV71 to prevent infection.

Poly(methyl methacrylate) microchip device integrated with gold nanoelectrode ensemble for in-column biochemical reaction and electrochemical detection.

This paper proposes a poly(methyl methacrylate) (PMMA) based microchip with an integrated gold nanoelectrode ensemble (GNEE) and a quartet-T loading channel for in-column urea/urease reactions and electrochemical detections. The on-chip GNEE electrode is fabricated using an electrodeless deposition process on a thin polycarbonate (PC) film and bonded directly onto a PMMA substrate to carry out high-performance electrochemical detections. The in-column bio-catalytic reaction of urea/urease is successfully demonstrated utilizing a novel approach based on the different electrokinetic mobilities of urea and urease in capillary electrophoresis (CE) channel. The experimental results significantly show that the GNEE electrode provides a better detection response for the reaction product of ammonia (NH(4)(+)) than a conventional planar gold electrode. The detection results demonstrate a satisfactory determination coefficient (R(2) value) and high reproducibility with a detection limit of 14.8 and 62.8 microM while detecting standard ammonia solution and the urea/urease reaction product of NH(4)(+), respectively. These results confirm the capability of the proposed device for the high-resolution CE-electrochemical detection (CE-ED) of bioanalytical reactions.

Ultra-sensitive detection of mutated papillary thyroid carcinoma DNA using square wave stripping voltammetry method and amplified gold nanoparticle biomarkers.

This study presents an ultra-sensitive technique for the electrochemical detection of the mutated BRAF gene associated with papillary thyroid carcinomas (PTC). In the proposed approach, a biotinylated 30-nucleotides probe DNA was immobilized in a streptavidin-modified 96-well microtiter plate and the free active sites of the streptavidin were blocked using biotinylated bovine serum albumin (BSA). The biotinylated target DNA was then added and allowed to hybridize with the immobilized probe DNA for 30min. Subsequently, streptavidin-labeled gold nanoparticles were added, and a nanoparticle enlargement process was performed using gold ion solution and formaldehyde reductant. The gold particles were then dissolved in bromide and DNA hybridization detection process was performed using a square wave stripping voltammetry (SWSV) technique. The results indicated a stable SWSV response in differential detection between blank solution and target DNA solution with a concentration of 130aM. Moreover, the coefficient of determination (R(2)) of the semi-log plot of the SWSV response current against the target DNA concentration (0.52-1300aM) was found to be 0.9982. The detection limit was estimated to be 0.35aM (based on a signal-to-noise ratio of 3:1). This value was approximately three orders of magnitude lower than that obtained using the same method but without gold amplification process. Finally, the proposed approach is successful in differentiating between the mutant and wildtype BRAF sequences that are present in genuine 224-nucleotides DNA.

Digital pulse ac voltammetry for the simultaneous analysis of electroactive and electrosorptive species in flow systems.

A digital two-step and three-step pulse potential ac voltammetry system was proposed and applied for the simultaneous analysis of electrosorptive and electroactive species in flow systems. To perform the ac polarography function, a PC was interfaced to a potentiostat to mimic all the necessary hardware functions of an analog ac polarograph. From the measurement of the change of phase-selective charging current and the zero-order current, I(3)(-), Br(-) specifically adsorbed and Cd(2+), Pb(2+) reduced at a hanging mercury drop electrode can be determined simultaneously in a FIA and IC system. With the digital pulse ac voltammetry-coupled IC, detection limits as low as 5.0 microM and linear dynamic ranges from 5.0 to 100 or 200 microM with linear correlation coefficients better than 0.9990 were found for the analysis of I(3)(-), Br(-), and S(2)O(3)(2)(-).

Immunoassay with a microtiter plate incorporated multichannel electrochemical detection system.

To extend the application of a multichannel electrochemical detector (MED) for immunoassay, a MED system consisting of 8 sets of Pt electrodes in an arrangement fitted with the dimensions of a row of microtiter wells in a microtiter plate and a microcomputer-assisted 16-channel potentiostat was constructed. With this developed MED system, electroactive enzymatic products produced in eight microtiter wells can be analyzed simultaneously with a developed amperometric procedure. To demonstrate the applicability of the MED system for immunoassay, an immunosystem containing rabbit-IgG and alkaline phosphatase-conjugated goat anti rabbit-IgG was studied. From the dynamic range of 10-1000 ng/mL (0.064-6.4 pM) and the detection limit of 1.0 ng/mL (6.4 pM) obtained, the developed MED shows a tremendous improvement in sensitivity, detection limit, and efficiency compared with that obtained from conventional electrochemical immunoassay.