Codelivery of Doxorubicin and p53 Gene by ß-Cyclodextrin-Based Supramolecular Nanoparticles Formed via Host-Guest Complexation and Electrostatic Interaction.

We developed a supramolecular system for codelivery of doxorubicin (Dox) and p53 gene based on a ß-CD-containing star-shaped cationic polymer. First, a star-shaped cationic polymer consisting of a ß-CD core and 3 arms of oligoethylenimine (OEI), named CD-OEI, was used to form a supramolecular inclusion complex with hydrophobic Dox. The CD-OEI/Dox complex was subsequently used to condense plasmid DNA via electrostatic interactions to form CD-OEI/Dox/DNA polyplex nanoparticles with positive surface charges that enhanced the cellular uptake of both Dox and DNA. This supramolecular drug and gene codelivery system showed high gene transfection efficiency and effective protein expression in cancer cells. The codelivery of Dox and DNA encoding the p53 gene resulted in reduced cell viability and enhanced antitumor effects at low Dox concentrations. With its enhanced cellular uptake and anticancer efficacy, the system holds promise as a delivery carrier for potential combination cancer therapies.

Nontoxic, Biodegradable Hyperbranched Poly(ß-amino ester)s for Efficient siRNA Delivery and Gene Silencing.

RNA interference (RNAi)-mediated gene silencing is a promising therapeutic approach to treat various diseases, but safe and efficient delivery remains a major challenge to its clinical application. Non-viral gene vectors, such as poly(ß-amino esters) (pBAEs), have emerged as a potential candidate due to their biodegradability, low toxicity profile, ease of synthesis, and high gene transfection efficiency for both DNA and siRNA delivery. However, achieving significant gene silencing using pBAEs often requires a large amount of polymer carrier (with polymer/siRNA weight ratio >100) or high siRNA dose (>100 nM), which might potentially exacerbate toxicity concerns during delivery. To overcome these barriers, we designed and optimized a series of hyperbranched pBAEs capable of efficiently condensing siRNA and achieving excellent silencing efficiency at a lower polymer/siRNA weight ratio (w/w) and siRNA dose. Through modulation of monomer combinations and branching density, we identified the top-performing hyperbranched pBAEs, named as h(A2B3)-1, which possess good siRNA condensation ability, low cytotoxicity, and high cellular uptake efficiency. Compared with Lipofectamine 2000, h(A2B3)-1 achieved lower cytotoxicity and higher siRNA silencing efficiency in HeLa cells at a polymer/siRNA weight ratio of 30 and 30 nM siRNA dose. Notably, h(A2B3)-1 enhanced the gene uptake in primary neural cells and effectively silenced the target gene in hard-to-transfect primary cortical neurons and oligodendrocyte progenitor cells, with gene knockdown efficiencies of 34.8 and 53.4% respectively. By incorporating a bioreducible disulfide compartment into the polymer backbone, the cytocompatibility of the h(A2B3)-1 was greatly enhanced while maintaining their good transfection efficiency. Together, the low cytotoxicity and high siRNA transfection efficiency of hyperbranched h(A2B3)-1 in this study demonstrated their great potential as a non-viral gene vector for efficient siRNA delivery and RNAi-mediated gene silencing. This provides valuable insight into the future development of safe and efficient non-viral siRNA delivery systems as well as their translation into clinical applications.

Designer co-beta-peptide copolymer selectively targets resistant and biofilm Gram-negative bacteria.

New antimicrobials are urgently needed to combat Gram-negative bacteria, particularly multi-drug resistant (MDR) and phenotypically resistant biofilm species. At present, only sequence-defined alpha-peptides (e.g. polymyxin B) can selectively target Gram-negative bacterial lipopolysaccharides. We show that a copolymer, without a defined sequence, shows good potency against MDR Gram-negative bacteria including its biofilm form. The tapered blocky co-beta-peptide with controlled N-terminal hydrophobicity (#4) has strong interaction with the Gram-negative bacterial lipopolysaccharides via its backbone through electrostatic and hydrogen bonding interactions but not the Gram-positive bacterial and mammalian cell membranes so that this copolymer is non-toxic to these two latter cell types. The new #4 co-beta-peptide selectively kills Gram-negative bacteria with low cytotoxicity both in vitro and in a mouse biofilm wound infection model. This strategy provides a new concept for the design of Gram-negative selective antimicrobial peptidomimetics against MDR and biofilm species.

Surface Charge Switchable Polymer/DNA Nanoparticles Responsive to Tumor Extracellular pH for Tumor-Triggered Enhanced Gene Delivery.

A tumor-targeted surface charge switchable polymeric gene delivery system with the function of switching surface charge upon reaching the tumor site owing to the tumor extracellular pH (pHe) was developed. The delivery system was fabricated by two steps. First, the positively charged polyplexe nanoparticles were formed between ß-cyclodextrin-oligoethylenimine star polymer (CD-OEI) and plasmid DNA (pDNA). Next, the CD-OEI/pDNA polyplex nanoparticles were coated with a pHe-responsive anionic polymer via an electrostatic interaction to form ternary complexes. The pHe-responsive anionic polymer was block copolymers of poly(ethylene glycol) (PEG) and poly(2-aminoethyl methacrylate) (pAEMA) modified with 2,3-dimethylmaleic anhydride (denoted as PPD). The coating polymer was mixed with a small amount of pHe-insensitive PEG-pAEMA modified with succinic anhydride (denoted as PPS), giving a balanced negatively charged and PEG-shielded surface with a pHe-responsive property for achieving the expected tumor-triggered enhanced gene delivery. At physiological pH 7.4, owing to the charge shielding of anionic surface coating and the PEGylation, the negatively charged CD-OEI/pDNA/PPD+PPS polyplex complexes could avoid the undesirable interaction with serum proteins and nontargeted components. However, the amide bond of PPD was sensitive to pH changes and could be easily hydrolyzed under acidic pHe (<6.8) to expose the primary amine group due to nucleophile catalysis by the carboxylic acid. The PEG block in the copolymers was used to further enhance the surface-shielding effect. Our data showed that excellent particle salt stability and serum tolerance were achieved through the PPD+PPS surface coating. The CD-OEI/pDNA/PPD+PPS complexes achieved lower cellular uptake and transfection efficiency at neutral pH 7.4 while exhibiting comparable cellular uptake and transfection efficiency at acidic pH 6.5 as compared to the uncoated polyplexes, indicating that the surface charge switching worked well.

WS2 Nano-petals and Nano-bristles Supported on Carbon Nanotubes for Electron Emission Applications.

Atomically thin WS2 nano-petals and nano-bristles were synthesized on vertically aligned carbon nanotubes (CNT) via magnetron sputtering at room temperature. The formation of the nano-petal morphology requires reaching a critical threshold in sputter deposition time, below which an amorphous film of WO3 is obtained instead. Increasing the deposition time past a second threshold results in a change to the nano-bristle morphology. Both WS2 nano-petals and nano-bristles were able to significantly enhance the electron emission of properties. The lowest turn-on voltage measured was to be 295 V and 355 V for the nano-petals and nano-bristles respectively, versus 425 V for pristine CNTs. The variation in the turn-on voltage is due to the electrical contacts at the interface between the different WS2 structures, which induces current saturation at high emission currents. These results demonstrate that 2D WS2 layers can be synthesized without the need for chemical routes and high growth temperatures if an appropriate template is employed.