Xiaoliang Qi

Investigation of Salecan/poly(vinyl alcohol) hydrogels prepared by freeze/thaw method.

Salecan is a novel water-soluble extracellular-glucan produced by a new kind of salt-tolerant strain Agrobacterium sp. ZX09 and can be applied in food and medicine industries. In this work, Salecan (Sal) was incorporated into poly(vinyl alcohol) (PVA) to prepare novel Sal/PVA hybrid hydrogels by repeated freeze-thaw processing. Physicochemical and biological characteristics of the hydrogels were investigated to evaluate their potential as cell adhesion materials. By increasing the Salecan content in the hybrid hydrogels, their swelling capacity increased notably, while the compressive modulus decreased. Observed by SEM, Sal/PVA hydrogels had a homogeneous porous structure. The degradation rate of the hydrogels can be controlled by tailoring the composition ratio of Sal/PVA. Furthermore, cells could adhere well on the surface of Sal/PVA hydrogels. In conclusion, these results make Sal/PVA hydrogels attractive materials for biomedical applications.

A novel thermo-responsive hydrogel based on salecan and poly(N-isopropylacrylamide): Synthesis and characterization

Salecan is a novel microbial polysaccharide produced by Agrobacterium sp. ZX09. The salt-tolerant strain was isolated from a soil sample in our laboratory and the 16S rDNA sequence was deposited in the GenBank database under the accession number GU810841. Salecan is suitable to fabricate hydrogel for biomedical applications due to the excellent hydrophilicity and biocompatibility. Here, salecan has been introduced into poly(N-isopropylacrylamide) (PNIPAm) network to form novel thermo-sensitive semi-interpenetrating polymer networks (semi-IPNs). The structure of salecan/PNIPAm semi-IPNs was confirmed by Fourier transformation infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Thermogravimetric analysis (TGA) proved the stability of the semi-IPNs. Rheological and compressive tests revealed an elastic solid-like behavior and good mechanical properties of the hydrogels. Swelling behavior test showed the hydrogels possessed high water content at room temperature. An excellent thermo-sensitive property of fast response rates to temperature had been demonstrated as well. In vitro degradation measurements ensured the semi-IPNs were degradable. Cytotoxicity and cell adhesion study suggested the synthesized salecan/PNIPAm hydrogels were non-toxic and biocompatibility. The results indicated the novel thermo-responsive hydrogels could be a suitable candidate for biomedical applications.

Salecan-Based pH-Sensitive Hydrogels for Insulin Delivery

Stimuli-responsive polymeric hydrogels are promising and appealing delivery vehicles for protein/peptide drugs and have made protein/peptide delivery with both dosage- and spatiotemporal-controlled manners possible. Here a series of new Salecan-based pH-sensitive hydrogels were fabricated for controlled insulin delivery via the graft copolymerization reaction between Salecan and 2-acrylamido-2-methyl-1-propanesulfonic acid. In this study, on one hand, Salecan played a key role in modifying the structure and the pore size of the developing hydrogel. On the other hand, Salecan tuned the water content and the water release rate of the obtained hydrogel, leading to a controllable release rate of the insulin. More importantly, in vitro release experiments validated that the release of insulin from this intelligent system could be also tailored by the environmental pH of the release medium. For SGA2, the amount of encapsulated insulin released at gastric conditions (pH 1.2) was relatively low (about 26.1 wt % in 24 h), while that released at intestinal conditions (pH 7.4) increased significantly (over 50 wt % in 6 h). Furthermore, toxicity assays demonstrated that the designed hydrogel carriers were biocompatible. These characteristics make the Salecan-based hydrogel a promising candidate for protein/peptide drug delivery device.

Development of novel hydrogels based on Salecan and poly(N-isopropylacrylamide-co-methacrylic acid) for controlled doxorubicin release

Salecan is a novel water-soluble extracellular polysaccharide composed of a linear repeating unit of 1-3-linked glucopyranosyl. Salecan is suitable for the preparation of hydrogels for biomedical applications due to its outstanding biological and physicochemical profiles. Here we designed a novel semi-interpenetrating polymer network (semi-IPN) hydrogel that incorporated the hydrophilic polysaccharide Salecan into a stimuli-responsive poly(N-isopropylacrylamide-co-methacrylic acid) (PNM) hydrogel matrix for controlled drug release. In this research, on one hand, Salecan modified the architecture and the pore size of the semi-IPN network. On the other hand, Salecan played a vital role in modulating water content and tuning the water release rate of the developing hydrogel, resulting in an adjustable release rate of the drugs. Doxorubicin (DOX), an anticancer drug, was loaded into the semi-IPN hydrogels as a model drug, and the in vitro release assay exhibited that the release rate was closely related to the content of introduced Salecan, as well as the environmental temperature and pH of the release media. Cytotoxicity experiments demonstrated that all blank semi-IPN hydrogels were non-toxic to HepG2 and A549 cells, while drug released from the DOX-loaded hydrogels could still exert its pharmacological activity and had the ability to kill these two cancer cells. Altogether, this work provides a way to synthesize a new type of hydrogel as general drug delivery vectors with a desired release rate.

Synthesis and Characterization of a Multi-Sensitive Polysaccharide Hydrogel for Drug Delivery

Salecan is a novel water soluble polysaccharide produced by a salt-tolerant strain Agrobacterium sp. ZX09. Poly(dimethylaminoethyl methacrylate) (PDMAEMA) is a pH, thermo, and ionic strength multi-sensitive polymer with anti-bacterial property. Here, we report a semi-interpenetrating polymer network (semi-IPN) hydrogel based on salecan and PDMAEMA. The obtained hydrogel is simultaneous sensitive to pH, ionic strength and temperature: the swelling ratio maximizes at pH 1.2 and shrinks at pH value greater than 3; besides, water content of the hydrogel decreases as the ionic strength increases; in terms of temperature, the hydrogel swells/deswells at temperatures below/above 40°C. Cytotoxicity test shows the hydrogel is non-cytotoxic to COS-7 cells. Protein drug insulin was selected as model drug to test the in vitro release behavior of the hydrogel. Results show the release rate increases with the swelling ratio of the hydrogel. In addition, when the temperature is higher than the lower critical solution temperature (LCST) of PDMAEMA, the hydrogel shrinks to extrude more drug molecules. Moreover, the release rate and release amount were higher in acid condition (pH 1.2) than at pH 7.4. In summary, this polysaccharide hydrogel is a promising material for drug delivery.

Design of Salecan-containing semi-IPN hydrogel for amoxicillin delivery

Salecan is a new linear extracellular β-glucan. The unique structure and beneficial properties of Salecan makes it an appealing material in biomedical applications. In this work, novel drug devices based on Salecan in a hydrogel matrix of poly(N-(3-dimethylaminopropyl)acrylamide-co-acrylamide) (Salecan/PDA) were fabricated via free radical polymerization for controlled release of amoxicillin. It was demonstrated that amoxicillin was efficiently encapsulated into the developed hydrogels and released in a Salecan dose-dependent and pH-sensitive manner. Furthermore, cell toxicity and adhesion assays confirmed that these drug carriers were biocompatible. Altogether, this study opens a new avenue to fabricate hydrogel devices for controlled delivery of drug.

Rational design, synthesis of reaction-based dual-channel cyanide sensor in aqueous solution

A new dual-channel sensor for the detection of cyanide was developed based on the conjugated of naphthalene and malononitrile. Upon the addition of CN(-), the sensor displayed very large blue-shift in both fluorescence (80nm) and absorption (120nm) spectra. The sensor of cyanide was performed via the nucleophilic attack of cyanide anion to vinylic groups of the sensor with a 1:1 binding stoichiometry and the color changed of the sensor is mainly due to the intramolecular charge transfer process improvement. The intramolecular charge transfer progress was blocked with color changed and fluorescence blue-shift. The mechanism of sensor reaction with CN(-) ion was studied using (1)H NMR and mass spectrometry.

Cationic Salecan-based hydrogels for release of 5-fluorouracil

Salecan, a new water-soluble β-glucan, has excellent physicochemical and biological characteristics. Here, a series of pH-sensitive hydrogels based on Salecan grafted with [2-(methacryloxy)ethyl]trimethylammonium chloride were developed for controlled drug delivery. The successful preparation of the grafted hydrogels was confirmed by Fourier transform infrared spectroscopy, X-ray diffraction, and thermogravimetric analysis. After that, rheology and scanning electron microscopy tests showed that the mechanical and morphological properties of these hydrogels were strongly influenced by the Salecan content. Moreover, the swelling behavior of the resulting hydrogels was systematically studied, and the results suggested that they exhibited pH sensitivity. Loading and delivery experiments demonstrated that 5-fluorouracil was efficiently encapsulated into the hydrogel matrices and released in a predictable manner via pH and Salecan dose control. Finally, cell viability and adhesion assays verified the cell compatibility of the designed hydrogels. Altogether, these attributes make the Salecan-based graft hydrogel a promising platform for controlled 5-fluorouracil delivery.

Selective determination of Ag+ using Salecan derived nitrogen doped carbon dots as a fluorescent probe

We report that nitrogen doped carbon dots (N-CDs) represent a viable fluorescent probe for the determination of Ag+. The N-CDs can be fairly easily prepared by a hydrothermal treatment method using Salecan and dicyandiamide as the precursors, display excitation/emission maxima of 350/438nm. The N-CDs have an average diameter of about 3.8nm. The N-CDs exhibited blue fluorescence (quantum yield of 13.2%) and could response to Ag+ selectively and sensitively. Other ions nearly had no interference. The probe has excellent selectivity, high sensitivity, and a linear response range that extends from 0 to 40μM. The limit of detection is as low as 1.12×10-7mol/L. The method was applied to the determination of Ag+ dissolved in water.

Preparation of a Salecan/poly(2-acrylamido-2-methylpropanosulfonic acid-co-[2-(methacryloxy)ethyl]trimethylammonium chloride) Semi-IPN Hydrogel for Drug Delivery.

Salecan is a water‐soluble bacterial polysaccharide consisting of glucopyranosyl units linked by α‐1,3 and β‐1,3 glycosidic bonds. salecan is suitable for the development of hydrogels for biomedical applications, given its outstanding physicochemical and biological profiles. In this study we designed a new semi‐interpenetrating polymer network hydrogel that introduces the salecan polysaccharide into a stimuli‐responsive poly(2‐acrylamido‐2‐methylpropanosulfonic acid‐co‐[2‐(methacryloxy)ethyl]trimethylammonium chloride) (PAM) hydrogel matrix for controlled insulin release. We found that salecan not only tunes the structure and pore size of the PAM hydrogels, but also endows them with adjustable water release rates. More importantly, in vitro drug loading/release assays demonstrated that insulin is efficiently loaded into the resulting hydrogels and can be released in an on‐demand manner by controlling the pH and salecan dose. Furthermore, cell viability and cell adhesion experiments verified the cell compatibility of these hydrogel carriers. Together, these results make salecan‐incorporated PAM hydrogels promising materials for drug delivery.