A Probe for Fluorescence Detection of the Acetylcholinesterase Activity Based on Molecularly Imprinted Polymers Coated Carbon Dots.

This paper presents a new probe for fluorescence detection of the acetylcholinesterase (AChE) activity based on molecularly imprinted polymer (MIP) coated carbon dots (C-dots) composite. The C-dots were hydrothermally synthesized with grafted silica surface and sealed with molecularly imprinted polymers in silica pores (MIP@C-dots) in situ. Removed the original template molecules, the MIP@C-dots composite exhibits quite high selectivity for acetylthiocholine (ACh). With AChE, its substrate ACh will be hydrolyzed into thiocholine and the fluorescence signals exhibit a dramatic decrease at 465 nm, Under optimal conditions, the fluorescent probe shows sensitive responses to AChE in the range of 0.01-0.6 mU/mL. The detection limits of AChE are as low as 3 µU/mL. These experiments results validate the novel fluorescent probe based on MIP@C-dots composite, paving a new way to evaluation of AChE activity and Screening inhibitors.

Engineered redox-responsive PEG detachment mechanism in PEGylated nano-graphene oxide for intracellular drug delivery.

In biomedical applications, polyethylene glycol (PEG) functionalization has been a major approach to modify nanocarriers such as nano-graphene oxide for particular biological requirements. However, incorporation of a PEG shell poses a significant diffusion barrier that adversely affects the release of the loaded drugs. This study addresses this critical issue by employing a redox-responsive PEG detachment mechanism. A PEGylated nano-graphene oxide (NGO-SS-mPEG) with redox-responsive detachable PEG shell is developed that can rapidly release an encapsulated payload at tumor-relevant glutathione (GSH) levels. The PEG shell grafted onto NGO sheets gives the nanocomposite high physiological solubility and stability in circulation. It can selectively detach from NGO upon intracellular GSH stimulation. The surface-engineered structures are shown to accelerate the release of doxorubicin hydrochloride (DXR) from NGO-SS-mPEG 1.55 times faster than in the absence of GSH. Confocal microscopy shows clear evidence of NGO-SS-mPEG endocytosis in HeLa cells, mainly accumulated in cytoplasm. Furthermore, upon internalization of DXR-loaded NGO with a disulfide-linked PEG shell into HeLa cells, DXR is effectively released in the presence of an elevated GSH reducing environment, as observed in confocal microscopy and flow cytometric experiments. Importantly, inhibition of cell proliferation is directly correlated with increased intracellular GSH concentrations due to rapid DXR release.

Effective gene delivery using stimulus-responsive catiomer designed with redox-sensitive disulfide and acid-labile imine linkers.

A dual stimulus-responsive mPEG-SS-PLL(15)-glutaraldehyde star (mPEG-SS-PLL(15)-star) catiomer is developed and biologically evaluated. The catiomer system combines redox-sensitive removal of an external PEG shell with acid-induced escape from the endosomal compartment. The design rationale for PEG shell removal is to augment intracellular uptake of mPEG-SS-PLL(15)-star/DNA complexes in the presence of tumor-relevant glutathione (GSH) concentration, while the acid-induced dissociation is to accelerate the release of genetic payload following successful internalization into targeted cells. Size alterations of complexes in the presence of 10 mM GSH suggest stimulus-induced shedding of external PEG layers under redox conditions that intracellularly present in the tumor microenvironment. Dynamic laser light scattering experiments under endosomal pH conditions show rapid destabilization of mPEG-SS-PLL(15)-star/DNA complexes that is followed by facilitating efficient release of encapsulated DNA, as demonstrated by agarose gel electrophoresis. Biological efficacy assessment using pEGFP-C1 plasmid DNA encoding green fluorescence protein and pGL-3 plasmid DNA encoding luciferase as reporter genes indicate comparable transfection efficiency of 293T cells of the catiomer with a conventional polyethyleneimine (bPEI-25k)-based gene delivery system. These experimental results show that mPEG-SS-PLL(15)-star represents a promising design for future nonviral gene delivery applications with high DNA binding ability, low cytotoxicity, and high transfection efficiency.

Highly efficient drug delivery nanosystem via L-phenylalanine triggering based on supramolecular polymer micelles.

An intelligent drug delivery nanosystem has been developed based on biodegradable supramolecular polymer micelles (SMPMs). The drug release can be triggered from SMPMs responsively by a bioactive agent, L-phenylalanine in a controlled fashion. The SMPMs are constructed from ethylcellulose-graft-poly(ε-caprolactone) (EC-g-PCL) and α-cyclodextrin (α-CD) derivate via host-guest and hydrophobic interactions. It has been found that these SMPMs have disassembled rapidly in response to an additional L-phenylalanine, due to great affinity discrepancy to α-CD between L-phenylalanine and PCL. Experiments have been carried out on trigger-controlled in vitro drug release of the SMPMs loaded with a model porphyrin based photosensitizer THPP. The result shows that the SMPMs released over 85% THPP in 6 h, which is two orders magnitudes faster than that of control. Also investigated is the photodynamic therapy (PDT) of THPP-loaded SMPMs with and without L-phenylalanine on MCF-7 carcinoma cell line. An effective trigger-concentration dependent lethal effect has been found showing promise in clinical photodynamic therapy.

Cancer cell-nanomaterial interface: role of geometry and surface charge of nanocomposites in the capture efficiency and cell viability.

The nanomaterial-cell interface plays an important role in biodetection and therapy. Several parameters involved in the bio-nano interaction such as size, shape, surface charge, surface functionality and protein corona on the nanomaterials have been studied. Recently, we found that the surface charge of the cancer cell membrane derived from the glycolysis could be a general hallmark for cancer cell targeting and very efficient isolation by tailored nanoparticles. However, to simultaneously achieve high capture efficiency and optimal cell viability, the influence of critical features of nanomaterials, such as surface charge and geometry, must be explored. In this study, we designed and synthesized spherical core-shell magnetic particles and Fe3O4 particle coated graphene oxide nanosheets with a similar surface chemistry, charge and magnetization, but different geometries. Although the two-dimensional (2D) graphene oxide based nanocomposites possessed higher capture efficiency at a low working concentration as compared to the spherical nanocomposites, they also exhibited more obvious cytotoxicity. Different aspects of the mechanism underlying the higher cytotoxicity from the 2D nanomaterials were investigated. The results of this study can guide the design of versatile candidates for the isolation of cancer cells.

Fabrication of Konjac glucomannan-based composite hydrogel crosslinked by calcium hydroxide for promising lacrimal plugging purpose.

Swelling, mechanical strength, flexibility, and toughness are important parameters in hydrogel preparation for application in the human body. Herein, composite hydrogels were prepared using a mix of Konjac glucomannan (KGM), sodium alginate (SA), and polyvinyl alcohol (PVA) cross-linked by calcium hydroxide. The PVA/KGM/SA composite hydrogel showed a suitable swelling ratio and rate, as well as elasticity and flexibility. In addition, the elongation at break was 660.3%, with a breaking strength of 87.25 kPa and a compression modulus of 1.660 MPa. Rheological studies showed that the composite hydrogel was composed of a multiply cross-linked network involving chemical and physical interactions, thereby affecting the elasticity and flexibility of the gel. Interestingly, the composite gel network was reformed when the temperature decreased. In rabbit models of dry eye, the hydrogel effectively maintained the normal tear meniscus height and increased the low tear meniscus area. The results therefore showed that the PVA/KGM/SA gels not only provide a simple, effective, and safe method for the preparation of hydrogels, but also have potential applications in the treatment of dry eye syndrome.

Effects of core size and PEG coating layer of iron oxide nanoparticles on the distribution and metabolism in mice.

INTRODUCTION: In vivo distribution of polyethylene glycol (PEG)ylated functional nanoparticles is vital for determining their imaging function and therapeutic efficacy in nanomedicine. However, contradictory results have been reported regarding the effect of core size and PEG surface of the nanoparticles on biodistribution. METHODS: To clarify this ambiguous understanding, using iron oxide nanoparticles (IONPs) as a model system, we investigated the effect of core size and PEG molecule weights on in vivo distribution in mice. Three PEGylated IONPs, including 14 nm IONP@PEG2,000, 14 nm IONP@PEG5,000, and 22 nm IONP@PEG5,000, were prepared with a hydrodynamic size of 26, 34, and 81 nm, respectively. The blood pharmacokinetics and tissue distribution were investigated in detail. RESULTS: The results indicated that the PEG layer, rather than core size, played a dominant role in determining the half-life time of IONPs. Specifically, increased molecular weight of the PEG layer led to a longer half-life time. These PEGylated IONPs were mainly excreted by liver clearance. While the PEG molecular layer constituted the key factor to determine the clearance ratio, core size affected the clearance rate. CONCLUSION: Complete blood count analysis and histopathology suggested excellent biocompatibility of PEGylated IONPs for future clinical trials.

Rapidly disassembling nanomicelles with disulfide-linked PEG shells for glutathione-mediated intracellular drug delivery.

The synthesis and biological efficacy of novel nanomicelles that rapidly disassemble and release their encapsulated payload intracellularly under tumor-relevant glutathione (GSH) levels are reported. The unique design includes a PEG-sheddable shell and poly(ε-benzyloxycarbonyl-l-lysine) core with a redox-sensitive disulfide linkage.

Novel vesicles self-assembled from amphiphilic star-armed PEG/polypeptide hybrid copolymers for drug delivery.

A novel amphiphilic four-armed [poly(ε-benzyloxycarbonyl-L-lysine)]2-block-poly(ethylene glycol)-block-[poly(ε-benzyloxycarbonyl-L-lysine)]2 hybrid copolymer has been prepared. The cytotoxicity study shows that the copolymer has good biocompatibility with no obvious inhibition effect on cell growth. The amphiphilic copolymers could self-assemble to form vesicles in aqueous solution. DOX · HCl, as a hydrophilic drug, can be loaded into the vesicles, and then successfully internalized by human breast cancer MCF-7 cells. Importantly, the DOX-loaded vesicles show a greatly improved drug release behavior with a zero-order release at the initial stage, suggesting a great potential as the carrier of hydrophilic drugs for controlled drug delivery.

Self-assembling nanomicelles of a novel camptothecin prodrug engineered with a redox-responsive release mechanism.

A novel amphiphilic camptothecin prodrug that spontaneously arranges into nanomicelles which preferentially release the cytotoxic drug under tumor-relevant reductive conditions is designed.