Bingyang Shi

Controlling upconversion nanocrystals for emerging applications

Lanthanide-doped upconversion nanocrystals enable anti-Stokes emission with pump intensities several orders of magnitude lower than required by conventional nonlinear optical techniques. Their exceptional properties, namely large anti-Stokes shifts, sharp emission spectra and long excited-state lifetimes, have led to a diversity of applications. Here, we review upconversion nanocrystals from the perspective of fundamental concepts and examine the technical challenges in relation to emission colour tuning and luminescence enhancement. In particular, we highlight the advances in functionalization strategies that enable the broad utility of upconversion nanocrystals for multimodal imaging, cancer therapy, volumetric displays and photonics.

Developing functionalized dendrimer-like silica nanoparticles with hierarchical pores as advanced delivery nanocarriers

Functionalized dendrimer-like hybrid silica nanoparticles with hierarchical pores are designed and synthesized. The unique structure, large surface area, and excellent biocompability render such materials attractive nanocarriers for the advanced delivery of various sized drugs and genes simultaneously.

Exploring N-Imidazolyl-O-Carboxymethyl Chitosan for High Performance Gene Delivery

Chitosan shows good biocompatibility and biodegradability, but the poor water solubility and low transfection efficiency hinder its applications as a gene delivery vector. We here report the detailed synthesis and characterization of a novel ampholytical chitosan derivative, N-imidazolyl-O-carboxymethyl chitosan (IOCMCS), used for high performance gene delivery. After chemical modification, the solubility of the resulting polymer is enhanced, and the polymer is soluble in a wide pH range (4-10). Gel electrophoresis study reveals the strong binding ability between plasmid DNA and the IOCMCS. Moreover, the IOCMCS does not induce remarkable cytotoxicity against human embryonic kidney (HEK293T) cells. The cell transfection results with HEK293T cells using the IOCMCS as gene delivery vector demonstrate the high transfection efficiency, which is dependent on the degree of imidazolyl substitution. Therefore, the IOCMCS is a promising candidate as the DNA delivery vector in gene therapy due to its high solubility, high gene binding capability, low cytotoxicity, and high gene transfection efficiency.

Label-free dendrimer-like silica nanohybrids for traceable and controlled gene delivery

To create advanced functional nanocarriers for achieving excellent gene delivery performance, fluorescence label-free hybridized dendrimer-like silica nanocarriers (HPSNs-AC-PEI) were developed by using the endosomal pH and cytoplasmic glutathione (GSH) responsive autofluorescent acetaldehyde-modified-cystine (AC) to link non-toxic low molecular weight branched polyethyleneimine (PEI) onto amino-functionalized dendrimer-like silica nanoparticles with hierarchical pores (HPSNs-NH2). The specific microstructure of this hybridized nanocarrier makes it not only show low cytotoxicity and high gene loading capability, but also display high gene transfection efficiency. The cleavage of disulfide bonds caused by GSH facilitates plasmid DNA (pDNA) release. Moreover, the pH and GSH controlled gene delivery profile can be real-time tracked using the autofluorescence of HPSNs-AC-PEI.

Developing a chitosan supported imidazole Schiff-base for high-efficiency gene delivery

A chitosan supported imidazole Schiff-base (CISB) has been developed to be used as the vector for high performance gene delivery. Introducing the imidazole Schiff-base to the branch of chitosan could improve its water solubility and gene binding ability under physiological conditions, and thus significantly enhance gene delivery capability due to the formation of Schiff-bases (azomethines) and the substitution of imidazole functional groups along chitosan backbones. Gel electrophoresis and light scattering results show that the CISB could effectively bind plasmid DNA (pDNA) and protect pDNA from DNase I digestion in solution. The CISB does not induce remarkable cytotoxicity against HEK 293 cells and can enhance delivery of pDNA into cytoplasm and nucleus efficiently. A transfection efficiency of 70% can be reached after systematically optimizing cell transfection conditions. Therefore, the CISB is a promising gene delivery vector due to its high solubility in physiological pH, strong gene binding and protection capability, low cytotoxicity, good biodegradability, and high efficiency in gene delivery and cell transfection.

Intracellular Microenvironment Responsive Polymers: A Multiple-stage Transport Platform for High-Performance Gene Delivery

A new strategy for promoting endoplasmic gene delivery and nucleus uptake is proposed by developing intracellular microenvironment responsive biocompatible polymers. This delivery system can efficiently load and self-assemble nucleic acids into nano-structured polyplexes at a neutral pH, release smaller imidazole-gene complexes from the polymer backbones at intracellular endosomal pH, transport nucleic acids into nucleus through intracellular environment responsive multiple-stage gene delivery, thus leading to a high cell transfection efficiency.

Exploring low-positively charged thermosensitive copolymers as gene delivery vectors

One of the largest challenges in gene therapy is to develop an efficient delivery vector without cytotoxicity. In this study, we propose a new concept in exploring low-positively charged thermosensitive copolymers as gene delivery vectors. Two types of copolymers, random copolymers (RCs) and blocky random copolymers (BRCs) of P(NIPAAm-co-HEMA-co-DMAEMA), are synthesized by free radical polymerization. Dynamic light scattering (DLS) and light transmittance measurements demonstrate the thermosensitive property and sharp phase transition behavior of the synthesized copolymers. Both RCs and BRCs exhibit proton buffering capacity. Cell viability assays indicate the low cytotoxicity from BRCs and almost no cytotoxicity from RCs which is ascribed to the presence of low positive charges along copolymer backbones. Such properties facilitate plasmid DNA (pDNA) delivery applications. The complexation of pDNA and RCs is detected by agarose gel electrophoresis and DLS. Furthermore, RCs are used as DNA delivery vectors to deliver green fluorescent protein (GFP) gene into HEK293T cells. The transfection efficiency is evaluated by GFP protein expression, which is affected by the charge content and transfection operation temperature. Lowering the temperature to 25 °C during the transfection course improves transfection efficiency, which results from the polyplexes dissociation at the temperature below the lower critical solution temperature (LCST). Our results reinforce that the new concept for efficient gene delivery without cytotoxicity at the transfection dose is achieved by using low-positively charged thermosensitive copolymer vectors.

Exploring thermal reversible hydrogels for stem cell expansion in three-dimensions

In this study, we report the application of a biocompatible thermo-reversible hydrogel, made from thermo-sensitive poly(N-isopropylacrylamide-co-acrylic acid) (P(NIPAM-AA)) microgels, for expanding stem cells in three-dimensions (3-D). The P(NIPAM-AA) microgels were synthesized by emulsion polymerization with their thermo-responsive phase transition behaviors being examined by light scattering and rheological methods. The viability of the microgel-exposed C3H/10T1/2 cells compared to the control cells is close to 100%, indicating the non-cytotoxicity of the synthesized microgels. At 37 °C, rheological measurements reveal the formation of hydrogels from 30 mg mL−1 microgel dispersions. The cross-sectional morphologies of the hydrogels show the interconnected porous structure. The 3-D stem cell culture system can be achieved by heating the microgel and cell mixtures to 37 °C. The increase of the viable stem cells cultured suggests that the in situ formed hydrogels support stem cell proliferation. The recovery of the 3-D cultured stem cells can be easily accomplished by cooling the culture system to room temperature. The released 3-D cultured cells can further adhere to a 2-D substrate, implying that the cultured stem cells are not only alive, but also retain the capability of migration. Therefore, the in situ formed thermo-reversible P(NIPAM-AA) hydrogels can be employed to expand stem cells in 3-D for further applications in tissue engineering.

Intracellular Fate of Nanoparticles with Polydopamine Surface Engineering and a Novel Strategy for Exocytosis-Inhibiting, Lysosome Impairment-Based Cancer Therapy

Polydopamine (PDA) coating as a bioinspired strategy for nanoparticles (NPs) has been extensively applied in cancer theranostics. However, a cellular-level understanding of nano-biointeraction of these PDA-coated NPs (PDNPs), which drives the fate of them and acts as a critical step to determine their efficacy, still remains unknown. Herein, we utilized the representative mesoporous silica NPs (MSNs) to be coated with PDA and study their nano-bioactivities in cancer cells. HeLa cell line was utilized as a model in this study. The PDNPs were discovered to be internalized through three specific pathways, that is, Caveolae-, Arf6-dependent endocytosis, and Rab34-mediated macropinocytosis (55%, 20% and 37% of uptake inhibition by nystatin, Arf6 knockdown, and rottlerin, respectively). Autophagy-mediated accumulation of PDNPs in lysosomes was observed and the formed PDA shells shedded in the lysosomes. Almost 40% of the NPs were transported out of cells via Rab8/10- and Rab3/26-mediated exocytosis pathways at our tested level. On the basis of these results, a novel combined cancer treatment strategy was further proposed using drug-loaded MSNs-PDA by (i) utilizing naturally intracellular mechanism-controlled PDA shedding for organelle-targeted release of drugs in lysosomes to generate lysosome impairment and (ii) blocking the demonstrated exocytosis pathways for enhanced therapeutic efficacy.

Intracellular Microenvironment‐Responsive Label‐Free Autofluorescent Nanogels for Traceable Gene Delivery

Gene therapy presents a unique opportunity for the treatment of genetic diseases, but the lack of multifunctional delivery systems has hindered its clinical applications. Here, a new delivery vector, autofluorescent polyethyleneimine (PEI) nanogels, for highly efficient and traceable gene delivery is developed. Different from commercial high-molecular-weight PEI, the cationic nanogels are noncytotoxic and able to be fragmented due to their unique intracellular microenvironment-responsive structures. The biodegradable nanogels can effectively load plasmid DNA (pDNA), and the self-assembled polyplexes can be cleaved after cellular uptake to improve gene transfection efficiency. Most importantly, the nanogels and the nanogel/pDNA polyplexes are autofluorescent. The fluorescence is stable in blood plasma and responsive to the intracellular microenvironment. The breakup of the nanogels or polyplexes leads to the loss of fluorescence, and thus the gene delivery and carrier biodegradation processes can be monitored. The reported multifunctional system demonstrates excellent biocompatibility, high transfection efficiency, responsive biodegradability, controlled gene release, label-free and simultaneous fluorescence tracking, which will provide a new platform for future scientific investigation and practical implications in gene therapy.