Shuiping Liu

Encapsulation of proteins in poly(L-lactide-co-caprolactone) fibers by emulsion electrospinning

This study was aimed at investigating emulsion electrospinning to prepare biodegradable fibrous mats with encapsulation of human-nerve growth factor (NGF). One of the best methods for fabricating a bio-functional tissue engineering scaffold is to load bioactive agent into the scaffold. In this work, the feasibility of incorporating NGF into poly(L-lactide-co-caprolactone) fibers by emulsion electrospinning has been studied. The release behavior of encapsulated bovine serum albumin (BSA) was investigated. The bioactivity of NGF released from fibrous mats was verified by testing the neurite outgrowth of rat pheochromocytoma cells (PC12). Furthermore, the process of fiber forming during emulsion electrospinning was discussed. The results demonstrate that emulsion electrospun fibers can successfully encapsulate proteins and release them in a sustained manner. The bioactivity of NGF released from emulsion electrospun fibers was confirmed by PC12 bioassays.

A new strategy for synthesizing AgInS2 quantum dots emitting brightly in near-infrared window for in vivo imaging

A new strategy for fabricating water-dispersible AgInS2 quantum dots (QDs) with bright near-infrared (NIR) emission is demonstrated. A type of multidentate polymer (MDP) was synthesized and utilized as a compact capping ligand for the AgInS2 QDs. Using silver nitrate, indium acetate and sulfur-hydrazine hydrate complex as the precursors, MDP-capping AgInS2 QDs were synthesized in aqueous solution at room temperature. Characterization indicates that the MDP-capping AgInS2 QDs are highly photoluminescent in NIR window and possess good photostability. Also, the QDs are stable in different media and have low cytotoxicity. Nude mice photoluminescence imaging shows that the MDP-capping AgInS2 QDs can be well applied to in vivo imaging. These readily prepared NIR fluorescent nanocrystals have huge potential for biomedical applications.

Chitosan-based core-shell nanomaterials for pH-triggered release of anticancer drug and near-infrared bioimaging

As a naturally-abundant biopolymer, chitosan (CS) exhibit pH-sensitive structural transformation within a narrow pH range. Integrating hydrophobic groups to CS molecules gives modified CS polymers with more adjustable pH responsiveness. In this paper, near-infrared (NIR) photoluminescent Ag2S QDs capped by long-chain carboxylic acid were synthesized and then conjugated with CS via esterification reaction. The anticancer drug doxorubicin (DOX) has an affinity for the hydrophobic oleoyl groups and was entrapped by them to produce Ag2S(DOX)@CS nanospheres. A variety of experiments were performed to characterize the nanospheres. In vitro and in vivo experiments showed that the nanospheres can release DOX at lowered pH in tumor cells and have high antitumor efficacy. In addition, the strong NIR signal derived from the encapsulated Ag2S QDs makes real-time monitoring of the nanosphere distribution in a body possible. This study provides a new CS-based nanocomposite drug carrier for efficient cancer therapy.

Quantum dots-hyperbranched polyether hybrid nanospheres towards delivery and real-time detection of nitric oxide.

In this work, novel hybrid nanosphere vehicles were synthesized for nitric oxide (NO) donating and real-time detection. The hybrid nanosphere vehicles consist of cadmium selenide quantum dots (CdSe QDs) as NO fluorescent probes, and the modified hyperbranched polyether (mHP)-based diazeniumdiolates as NO donors, respectively. The nanospheres have spherical outline with dimension of ~127 nm. The data of systematic characterization demonstrated that the mHP-based hybrid nanosphere vehicles (QDs-mHP-NO) can release and real-time detect NO with the low limit of 25 nM, based on fluorescence quenching mechanism. The low cell-toxicity of QDs-mHP-NO nanospheres was verified by means of MTT assay on L929 cells viability. The QDs-mHP-NO nanospheres provide perspectives for designing a new class of biocompatible NO donating and imaging systems.

Fabrication, Surface Properties and Protein Encapsulation/Release Studies of Electrospun Gelatin Nanofibers

The aim of this study was to fabricate gelatin nanofibers by electrospinning and investigate the characteristics of these nanofibers. It has been reported that composite nanofibrous mats with drug impregnated in biocompatible and biodegradable polymer nanofibers can serve as tissue-engineering scaffolds with desired and controllable drug-release properties. The composite nanofibrous mats electrospun from a solution consisting of gelatin, bovine serum albumin (BSA, a model compound to simulate proteins), poly(ethylene glycol) sorbitan monolaurate (Tween-20) and 2,2,2-trifluoroethanol (TFE) were prepared and characterized. The BSA release profile in phosphate-buffered saline (PBS, pH 7.4) was recorded and analyzed. For comparison, nanofibrous mats electrospun from the solution containing gelatin and BSA were also prepared and assessed. The morphologies of the nanofibrous mats were examined by scanning electron microscopy; the surface hydrophilicity was measured by water contact angle method; and the protein-release profiles were recorded by analyzing BSA amount after immersing the electrospun nanofibrous mats in PBS for various time periods. The results indicated that the composite nanofibrous mats electrospun from the gelatin emulsion and/or solution had controllable protein-release behavior and they could be utilized as tissue-engineering scaffolds with protein encapsulated.

Facile Assembly of Oppositely Charged Silver Sulfide Nanoparticles into Photoluminescent Mesoporous Nanospheres

Inorganic mesoporous materials have been attracting increasing attention during the past decade. In the present work, photoluminescent Ag2S nanospheres with mesoporous structures were prepared by assembling Ag2S nanoparticles with opposite charges in aqueous phase. Without structure-directing templates, mesoporous Ag2S with well-ordered face-centered cubic superlattice structures and high specific surface area was obtained. The mesoporous Ag2S nanospheres had the same crystal phase as their precursors Ag2S nanoparticles. Different from their near-infrared emitting precursors, the mesoporous Ag2S nanospheres exhibited cyan emission under ultraviolet excitation. The large number of sulfur-related defects existing in the mesostructures is most likely responsible for the photoluminescence. This work provides new insights into fabricating photoluminescent mesostructured materials via scale-up strategy.

Controllable release of nitric oxide and doxorubicin from engineered nanospheres for synergistic tumor therapy

NaYF4:Yb,Er upconversion nanoparticles (UCNPs) capped with long-chain carboxylic acid were synthesized and then conjugated with chitosan (CS) in the aid of N-hydroxysuccinimide. The resultant nanocompound was integrated with doxorubicin (DOX) and Roussins black salt (RBS), a photosensitive nitric oxide (NO) donor to produce stimuli-responsive UCNPs(DOX)@CS-RBS nanospheres as nanocarriers for controllable drug delivery. On the one hand, the encapsulated UCNPs can efficiently absorb NIR photons and convert them into visible photons to trigger NO release. On the other hand, the entrapped DOX can be released at lowered pH from the swollen nanospheres caused by stretched oleoyl-CS chains under acidic conditions. The UCNPs(DOX)@CS-RBS nanospheres exhibit great therapeutic efficacy, which is attributable to the combination of NO and DOX releases based on NO dose-dependent mechanisms. This study highlights the controllable release of NO and DOX from the same nanocarriers and the synergistic therapeutic effect on tumors, which could give new insights into improving cancer nanotherapeutics. STATEMENT OF SIGNIFICANCE In this paper, core-shell structured UCNPs(DOX)@CS-RBS nanospheres have been designed and synthesized via a step-by-step procedure. The stimuli-responsive UCNPs(DOX)@CS-RBS nanospheres act as nanocarriers for controllable drug delivery towards cancer therapy. The encapsulated UCNPs can efficiently absorb NIR photons and convert them into visible light to trigger NO release. Meanwhile, the entrapped DOX can be released from the swollen nanospheres caused by stretched oleoyl-CS chains at lowered pH typical of intracellular environment. Synergistic cancer therapy will be achieved through the combination of NO and DOX releases based on NO dose-dependent mechanisms. This study provides new drug nanocarriers with high antitumor efficacy for synergistic cancer therapy.

Electrospinning of polyacrylonitrile nanofibers using strain-hardening spinning solutions

The electrospinning of polyacrylonitrile (PAN) fibers from strain-hardening PAN solutions was studied. The strain-hardening PAN electrospinning solutions were prepared by adding ultrahigh-molecular-weight PAN (UHMWPAN) into medium-molecular-weight PAN (MMWPAN) solutions. The strain-hardening behavior of the solutions was evidenced by the CaBER extensional rheological tests. In electrospinning of PAN nanofibers, the solutions containing UHMWPAN were found to be stable when large electric field intensity was applied at a constant source-target distance, different from the case that a solution without UHMWPAN was used. PAN nanofibers with smaller diameter (270 nm compared with 496 nm for the nanofibers containing no UHMWPAN) could be electrospun from the strain-hardening solutions at larger electric field intensity and no beaded fibers were observed. The results of X-ray diffraction (XRD) and mechanical tests showed that the crystallinity, crystal orientation and mechanical performance of electrospun PAN nanofibers were improved with the increase of electric field intensity.

Growth of photoluminescent Ag2Se nanowires from a simple precursor solution

Near-infrared (NIR) photoluminescent silver selenide (Ag2Se) nanowires were synthesized from a precursor solution containing silver nitrate, elemental selenium and hydrazine hydrate (N2H4·H2O). Elemental selenium was reduced by N2H4·H2O and then reacted with silver nitrate. N2H4 also coordinated with the precursors and the resulting Ag2Se nanowires. The single-crystalline Ag2Se nanowires (tetragonal α-Ag2Se) grown from the precursor solution had varying diameters depending on the reaction time. After storing at 60 °C for 24 h, Ag2Se nanowires emitting in the NIR window were obtained. With increasing diameter, the emission intensity decreased until the nanowires became non-photoluminescent. The photoluminescence lifetime and photostability of the Ag2Se nanowires were similar to those of Ag2Se quantum dots reported previously. We expect that these Ag2Se nanowires will hold a broad spectrum of applications in nanoscale optical or photoelectronic devices.

Solvents Regulation and Thermodynamic Control the Morphologies of Cu2O Nanocrystals

Various morphologies of Cu2O nanoparticles have been prepared in a facile method. The XRD, EDX and XPS have been adopted to verify the components of the deposits. The following parameters have been adjusted to investigate the mechanism of crystal growth: content of copper(II) acetate, reaction temperature, rate of octadecenoic acid/ethanol/water. Experiment data revealed that the nanostructures of product could be modulated through carefully control these parameters, which is expecting to be used for producing well ordered Cu2O nanocrystals in large scale.