Enzyme and Thermo Dual-stimuli Responsive DOX Carrier Based on PNIPAM Conjugated Mesoporous Silica

Background

Stimuli-responsive drug delivery systems have been proven to be a promising strategy to enhance tumor localization, overcome multidrug resistance (MDR), and reduce the side effects of chemotherapy agents.

Objectives

In this study, a temperature and redox dual stimuli-responsive system using mesoporous silica nanoparticles (MSNs) for targeted delivery of doxorubicin (DOX) was developed.

Methods

Mesoporous silica nanoparticles were capped with poly(N-isopropylacrylamide) (PNIPAM), a thermo-sensitive polymer, with atom transfer radical polymerization (ATRP) method, via disulfide bonds (DOX-MSN-S-S-PNIPAM) to attain a controlled system that releases DOX under glutathione-rich (GSH-rich) environments and temperatures above PNIPAM's lower critical solution temperature (LCST). Morphological and physicochemical properties of the nanoparticles were indicated using transmission electron microscopy (TEM), dynamic light scattering (DLS), energy-dispersive X-ray spectroscopy (EDS), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and Brunauer-Emmett-Teller (BET). The drug release tests were performed at 25°C and 41°C in the absence and presence of the DTT, and the obtained results confirmed the synergic effect of temperature and reductive agent on a dual responsive release profile with a 73% cumulative release at 41°C and reductive environment during 240 min.

Results

The average loaded drug content and encapsulation efficacy were reported as 42% and 29.5% at the drug: nanoparticle ratio of 1.5: 1. In vitro cytotoxicity assays on MCF-7 cell lines indicated significant viability decreased in cells exposed to DOX-MSN-S-S-PNIPAM compared to the free drug (DOX).

Conclusions

Based on the results, DOX-MSN-S-S-PNIPAM has shown much more efficiency with stimuli-responsive properties in comparison to DOX on MCF-7 cancer cell lines.

Pathobiology of H9N2 avian influenza virus in Japanese quail (Coturnix coturnix japonica)

Clinical signs, serologic response, viral contents of the trachea and intestine, and histopathological and ultrastructural changes of the tracheal epithelium of Japanese quail experimentally infected with field isolate of H9N2 avian influenza were studied. Vaccinated and unvaccinated quail were inoculated with 10(6.3) 50% embryo infectious dose/bird of A/ chicken/Iran/SH-110/99 (H9N2) virus via nasal inoculation. Clinical signs such as depression, ruffled feathers, diarrhea, and nasal and eye discharges were observed 6 days postinfection (PI). No mortality was observed; however, there was reduction in feed and water consumption and egg production. However, the serologic response of vaccinated challenged and unvaccinated challenged birds was not significantly different. Unvaccinated challenged quail showed more severe histopathologic reaction in their lungs and trachea. Hyperemia, edema, infiltration of inflammatory cells, and deciliation and sloughing of the tracheal epithelium were observed. Ultrastructural study showed dilatation of endoplasmic reticulum and degeneration of Golgi apparatus and cilia of the tracheal lining cells of respiratory epithelium.