3D printing technology has attracted much attention due to its high potential in scientific and industrial applications. As an outstanding 3D printing technology, two-photon polymerization (TPP) microfabrication has been applied in the fields of micro/nanophotonics, micro-electromechanical systems, microfluidics, biomedical implants and microdevices. In particular, TPP microfabrication is very useful in tissue engineering and drug delivery due to its powerful fabrication capability for precise microstructures with high spatial resolution on both the microscopic and the nanometric scale. The design and fabrication of 3D hydrogels widely used in tissue engineering and drug delivery has been an important research area of TPP microfabrication. The resolution is a key parameter for 3D hydrogels to simulate the native 3D environment in which the cells reside and the drug is controlled to release with optimal temporal and spatial distribution in vitro and in vivo. The resolution of 3D hydrogels largely depends on the efficiency of TPP initiators. In this paper, we will review the widely used photoresists, the development of TPP photoinitiators, the strategies for improving the resolution and the microfabrication of 3D hydrogels.
Charge-reversal functional gold nanoparticles first prepared by layer-by-layer technique were employed to deliver small interfering RNA (siRNA) and plasmid DNA into cancer cells. Polyacrylamide gel electrophoresis measurements of siRNA confirmed the occurrence of the charge-reversal property of functional gold nanoparticles. The expression efficiency of enhanced green fluorescent protein (EGFP) was improved by adjuvant transfection with charge-reversal functional gold nanoparticles, which also had much lower toxicity to cell proliferation. Lamin A/ C, an important nuclear envelope protein, was effectively silenced by lamin A/C-siRNA delivered by charge-reversal functional gold nanoparticles, whose knockdown efficiency was better than that of commercial Lipofectamine 2000. Confocal laser scanning microscopic images indicated that there was more cy5-siRNA distributed throughout the cytoplasm for cyanine 5-siRNA/ polyethyleneimine/cis-aconitic anhydride-functionalized poly(allylamine)/polyethyleneimine/11-mercaptoundecanoic acid-gold nanoparticle (cy5-siRNA/PEI/PAH-Cit/PEI/MUA-AuNP) complexes. These results demonstrate the feasibility of using charge-reversal functional gold nanoparticles as a means of improving the nucleic acid delivery efficiency.Keywords gold nanoparticles; charge-reversal polyelectrolyte; drug delivery; layer-by-layer assembly; siRNA delivery Over the past decade, due to good biocompatibility, easy synthesis, monodispersity, and ready functionalization, gold nanoparticles have emerged as an attractive candidate for delivery of various payloads into cells, such as small drug molecules or large biomolecules, 1-5 such as DNA and siRNA. [6][7][8][9][10][11][12][13] The intracellular release could be triggered by glutathione (GSH), 3 pH, or external (e.g., light) stimuli. 1,4,[14][15][16][17] siRNA has emerged recently as a promising method for biological research and holds great potential for treatment of human * Address correspondence to liangxj@nanoctr.cn. ⊥ These authors contributed equally to this work.
Supporting Information Available:Preparation process of charge-reversal polyelectrolyte-coated gold nanoparticles using layer-bylayer technique; TEM images of colloidal AuNPs after the coating steps; fluorescence microscope image of 293T cells transfected with DNA/PEI/PAH-Cit/PEI/MUA-AuNP complexes; and cell viability of HeLa cells treated with PEI/PAH-Cit/PEI/MUA-AuNPs and nucleic acid complexes by MTT assay. This material is available free of charge via the Internet at http://pubs.acs.org. [18][19][20] Nucleic acid was mostly loaded by gold nanoparticles through thiol linkages or electrostatic interaction with cationic gold nanoparticles. [6][7][8][9][10][11][12][13]21,22 Elbakry et al. first developed the PEI/siRNA/PEI-AuNP system to deliver siRNA into cells and knockdown the expression of target gene based on the self-assembly layer-by-layer technology. 11 PEI, which has strong escape capacity from the endosome due to its so-called "proton sponge" effect and is usually a gold standa...
A group of amphiphilic cationic polymers, methoxy polyethylene glycol-block-(polycaprolactonegraft-poly(2-(dimethylamino)ethyl methacrylate)) (PECD), were synthesized by combining ringopening polymerization (ROP) and atom transfer radical polymerization (ATRP) methods to form nanoparticles (NPs). The structures of these amphiphilic cationic polymers were characterized by 1 H NMR measurement. The PECD NPs have hydrophobic cores covered with hydrophilic PEG and cationic PDMAEMA chains. These self-assembly nanoparticles were characterized by dynamic light scattering (DLS) technique. PECD NPs can effectively condense DNA to form compact complexes of the size 65-160 nm suitable for gene delivery. The in vitro gene transfection studies of HeLa and HepG2 cells show that PECD NPs have better transfection efficiency compared to polyethylenimine (PEI) and Lipofectamine 2000 at low dose (N/P = 5). The cytotoxicity result shows that PECD NPs/DNA complexes at the optimal N/P ratio for transfection have comparable toxicity with PEI and Lipofectamine. These results indicate that PECD NPs have a great potential to be used as efficient polymeric carriers for gene transfection.
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