Preparation Of Salecan-based Hydrogels For Cell Adhesion And Drug Delivery

Salecan is a water-soluble bacterial polysaccharide produced by a salt-tolerant strain Agrobacterium sp.ZX09.Salecan exhibits fascinating rheological properties,biological activities like antioxidation and nontoxicity(edible safety),it could be used in the food and feed industry as a thickening agent and in the pharmaceutical industry for treating and preventing constipation.Moreover,Salecan possesses a high number of hydroxyl groups,located on the main chain,thereby making it possible to be chemically modulated in a controlled and specific fashion.Based on these excellent properties,in this article,we developed a series of Salecan-based hydrogels.We planned to investigate physicochemical behaviors of these novel Salecan-constructed hydrogels like structure,swelling,thermal stability,mechanical strength,morphology.Meanwhile,their biological properties such as cell adhesion and drug release were also studied to assess their potential biomedical applications.The main research contents and results are as follows:(1)Development of Salecan/PVA Freezing-Thawing hydrogels for cell adhesionPure PVA hydrogel has a dense struture without any apparent microporosity,and is difficult to degrade,which was bad for cell adhesion and tissue engineering.Interpenetrating Salecan polysaccharide with PVA network will form a porous gel structure.In the formed blend hydrogel,hydrogen bonds between hydroxyl groups of PVA and Salecan can maintain the mechanical properties of the whole network structure.The morphological characterization confirmed that the prepared gel had a uniform pore size(?10?m).By changing the ratio of PVA to polysaccharide and the number of freeze-thaw cycles,the pore size of Salecan/PVA hydrogels could be controlled,making cell adhesion behaviours of Salecan/PVA hydrogels can be precisely tuned to a specific pore size range.Cell adhesion experiments showed that COS-7 cells could not adsorb on pure polyvinyl alcohol surface,but they could grow on Salecan/PVA gel surface thanks to the homogeneous porous structure and good biocompatibility of Salecan/PVA hydrogels.These results indicated that Salecan/PVA hybrid cryogels may be a promisingmaterial for biomedical applications especially in cell adhesion and tissue engineering.(2)Fabrication and characterization of a novel anticancer drug delivery system:Salecan/poly(methacrylic acid)semi-interpenetrating polymer network hydrogelAnticancer drug carrier should be sensitive to pH:it greatly minimized the side effects to normal cells under physiological conditions by reducing premature drug loss and undergoing accelerated release in an acidic tumor environment.Considering this factor,the prepared Salecan/PMAA hydrogels were pH-senstive by introducing MAA into Salecan-based hydrogel matrix.In the current research,Doxribicin(DOX)was incorporated into the aforementioned hydrogels through electrostatic interactions between the negatively charged hydrogels and positively charged DOX molecules.Swelling properties of the Salecan/PMAA hydrogels were systematically investigated,and the results indicated that they exhibited pH sensitivity:they are almost unswellable at low pH(1.2 and 5.0)and swollen extensively at pH 7.4.Moreover,it was found that the DOX release from the Dox-loaded hydrogels was significantly accelerated when the pH of the release media decreased from 7.4 to 5.0.Toxicity assays confirmed that the blank hydrogels had negligible toxicity to normal cells,whereas the DOX-loaded hydrogels remained high in cytotoxicity for A549 and HepG2 cancer cells.All of these attributes implied that the new proposed semi-IPNs serve as potential drug delivery platforms for cancer therapy.(3)Synthesis of a novel pH-thermo responsive hydrogel based on Salecan and poly(N-isopropylacrylamide-co-methacrylic acid)for drug deliveryHere 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.(4)Preparation and characterization of a novel Salecan-g-poly(2-acrylamido-2-methyl-1-propanesulfonic acid)(Salecan-g-DAMPS)hydrogelPoly(2-acrylamido-2-methyl-1-propanesulfonic acid)(PAMPS)is a highly water-soluble polymer with a pKa of 1.5 capable of accepting or donating protons upon an environmental change in pH.The incorporation of sulfate groups imparts Salecan-based hydrogel responses to pH stimuli.The pH of the human stomach is about 2,so AMPS introduced Salecan hydrogels can be used as a carrier for gastric drug release.Here a series of new Salecan-based pH-sensitive hydrogels were fabricated.The effects of the content of Salecan in Salecan-g-PAMPS hydrogels on their physical,mechanical and biological properties were investigated.Swelling results suggested that Salecan-g-PAMPS hydrogel exhibited pH sensitivity:they are almost unswellable at pH 7.4 and swollen extensively at pH 1.2.Moreover,it was found that the Dox release from the Dox-loaded hydrogels was significantly accelerated when the pH of the release media decreased from 7.4 to 5.0.Drug release assay indicated that the insulin was markedly suppressed under acidic conditions(pH 1.2)such as in the stomach of human,while it was significantly enhanced in neutral environment(pH 7.4)imitating normal tissue.Cytotoxicity analysis demonstrated that these drug carriers were highly biocompatible in nature.Such characteristics suggested that the Salecan-g-PAMPS hydrogel may be an advantageous candidate for universal oral drug delivery vehicle.(5)Synthesis and characterization of a Salecan/poly(2-acrylamido-2-methyl-propanosul-fonic acid-co-[2-(methacryloxy)ethyl]trimethylammonium chloride)semi-IPN hydrogelPoly(AMPS-co-METAC)(PAM)hydrogel has a strong water absorption,but its biocompatibility is poor,which is unfavourable for the application in tissue engineering and drug release field.In order to address this drawback,hydrogels based on PAM as a matrix and Salecan as entrapped polymer have been fabricated.Scanning electron microscopy test demonstrated that the morphological behaviors of the resultant hydrogels were strongly affected by the content of Salecan.After that,scanning electron microscopy test showed that the morphological properties of these hydrogels were strongly influenced by the Salecan content.Moreover,the swelling behaviors of the resulting hydrogels were systematically studied,and the results suggested that they exhibited pH sensitivity.Loading and delivery experiments demonstrated that insulin was efficiently encapsulated into the hydrogel matrices and released in a predictable manner via pH control.Finally,cell viability and adhesion assays verified the cell compatibility of the designed hydrogels.Altogether,these attributes make the Salecan-based hydrogel a promising platform for controlled drug delivery.