Polyethylenimine (PEI) is one of the most potent synthetic gene delivery vectors because of its high transfection efficiency. Although PEI has been used as a delivery vehicle for a long while, its toxicity is always an issue for clinical applications. In this study, we introduced a low molecular weight PEI of 10 kilodaltons to chondroitin sulfate (CS) via a Michael addition method. By adjusting weight ratios between cationic PEI and anionic CS, the intermolecular or intramolecular, or both, electrostatic interactions of CS-modified PEI (CP) maintained good water solubility but lost some ability to permeate cell membranes. Thus, the cytotoxicity of PEI decreased without sacrificing its gene transfection efficiency. Three CP copolymers with different PEI contents were synthesized and used to prepare polyplexes with plasmid DNA. The pDNA-formed polyplex with a low PEI content (CP(L)) was least cytotoxic and had a transfection efficiency comparable to Lipofectamine/pDNA. The good uptake of CP(L)/pDNA into U87 cells was primarily based on clatherin-dependent and CD44-mediated endocytosis.

MicroRNA-128 (miR-128) is an attractive therapeutic molecule with powerful glioblastoma regulation properties. However, miR-128 lacks biological stability and leads to poor delivery efficacy in clinical applications. In our previous study, we demonstrated two effective transgene carriers, including polyethylenimine (PEI)-decorated superparamagnetic iron oxide nanoparticles (SPIONs) as well as chemically-conjugated chondroitin sulfate-PEI copolymers (CPs). In this contribution, we report optimized conditions for coating CPs onto the surfaces of SPIONs, forming CPIOs, for magneto-gene delivery systems. The optimized weight ratio of the CPs and SPIONs is 2 : 1, which resulted in the formation of a stable particle as a good transgene carrier. The hydrodynamic diameter of the CPIOs is ∼136 nm. The gel electrophoresis results demonstrate that the weight ratio of CPIO/DNA required to completely encapsulate pDNA is ≥3. The in vitro tests of CPIO/DNA were done in 293 T, CRL5802, and U87-MG cells in the presence and absence of an external magnetic field. The magnetofection efficiency of CPIO/DNA was measured in the three cell lines with or without fetal bovine serum (FBS). CPIO/DNA exhibited remarkably improved gene expression in the presence of the magnetic field and 10% FBS as compared with a gold non-viral standard, PEI/DNA, and a commercial magnetofection reagent, PolyMag/DNA. In addition, CPIO/DNA showed less cytotoxicity than PEI/DNA and PolyMag/DNA against the three cell lines. The transfection efficiency of the magnetoplex improved significantly with an assisted magnetic field. In miR-128 delivery, a microRNA plate array and fluorescence in situ hybridization were used to demonstrate that CPIO/pMIRNA-128 indeed expresses more miR-128 with the assisted magnetic field than without. In a biodistribution test, CPIO/Cy5-DNA showed higher accumulation at the tumor site where an external magnet is placed nearby.

Combining upconversion nanoparticles (UCNPs) and UV-sensitive polymers to form a smart drug delivery system (DDS) is a promising strategy to circumvent drawbacks of direct UV excitation in clinical applications. This study tuned up core–shell UCNPs with a shell thickness of 6 nm and emission wavelength falling in the ultraviolet region at 350 nm under near-infrared (NIR) light irradiation at 980 nm. An amphiphilic block copolymer with UV-responsive o-nitrobenzyl ester (ONB) next to a glutathione (GSH)-responsive disulfide linkage was synthesized and formulated into a polymersome. Core–shell UCNPs and doxorubicin (DOX) were simultaneously encapsulated into the polymersome during double emulsion for DDS. The combination of NIR light-inducing photolysis of the ONB linkage and GSH cleaving the disulfide linkage enhanced DOX release for chemotherapy. From in vitro evaluation, the polymersome alone was nontoxic against three lung cancer cell lines, but the one loaded with core–shell UCNPs and DOX showed severe cell-killing effect under the assistance of a 980 nm diode laser. In vivo study in A549 tumor-bearing mice verified significant inhibition of tumor growth in mice treated with the polymersome containing core–shell UCNPs and DOX under 980 nm diode laser irradiation as compared with those without laser irradiation and those treated with free DOX. This intriguing nanomedicine of well-defined structures responsive to NIR light and reducing agents offers potential for smart DDS applications.

Similar numbers of repeating units of PCL and pDMAEMA were controlled between L-PCL-PDMAEMA and S-PCL-PDMAEMA. DOX-loaded S-PCL-PDMAEMA micelles showed a better cell-killing effect than DOX-loaded L-PCL-PDMAEMA in four cell lines. The co-delivery of DOX and pDNA was confirmed by CLSM.