Hydrogels can offer many opportunities for drug delivery strategies. They can be used on their own or their benefits can be further exploited in combination with other nanocarriers. Intelligent hydrogels that react to changes in the surrounding environment can be utilized as gatekeepers and provide sustained on demand drug release. In this study, a hybrid nanosystem for tempera-ture and pH sensitive delivery was prepared from MCM-41 nanoparticles grafted with newly synthesized thermosensitive hydrogel (MCM-41/AA-g-PnVCL). The initial particles were chemi-cally modified by carboxyl groups attachment. Later, they were grafted with agar (AA) and vi-nylcaprolactam (VCL) by free radical polymerization. Doxorubicin was applied as a model hy-drophilic chemotherapeutic drug. The successful formulation was confirmed by FT-IR and TGA. Transmission electron microscopy and dynamic light scattering analysis showed small particles with negative zeta potential. Their release behaviour was investigated in vitro in different pH media and at different temperatures. At tumor simulating conditions (40ºC and pH 4.0) doxoru-bicin was almost completely released within 72 hours. The biocompatibility of the proposed na-noparticles was demonstrated by in vitro haemolysis assay. These results suggest the possible parenteral application of the newly prepared hydrogel-functionalized mesoporous silica nanopar-ticles for temperature-sensitive and pH-triggered drug delivery at the tumor site.

The cell surface targeting of neo-synthesized G protein coupled receptors (GPCRs) involves recruitment of receptor into COPII vesicles budding at Endoplasmic Reticulum Exit sites (ERES). This process is regulated for some GPCRs by escort proteins, which facilitate their export, or by gatekeepers that retain the receptors in the ER. PRAF2, an ER gatekeeper of the heterodimeric GABAB receptor protomer GB1, which interacts with a tandem di-leucine / RXR retention motif in the carboxyterminal tail of GB1, also inhibits the plasma membrane export of the chemokine receptor CCR5. PRAF2 / CCR5 interactions involve the transmembrane domains of both proteins. The di-leucine / RXR motif contained in the third intracellular loop of CCR5 does not affect PRAF2-mediated retention but impairs instead the interaction between CCR5 and its private escort protein CD4. PRAF2 and CD4 thus display opposite roles on the cell surface export of CCR5, likely at the level of its recruitment into COPII vesicles, PRAF2 inhibiting and CD4 promoting this process.