A novel multicompartimental system based on aminated poly(vinyl alcohol) microspheres/succinoylated pullulan microspheres for oral delivery of anionic drugs

Pullulan in biomedical research and development - A review

Pullulan is an imperative microbial exo-polymer commercially produced by yeast like fungus Aureobasidium pullulans. Its structure contains maltosyl repeating units which comprises two α-(1 → 4) linked glucopyranose rings attached to one glucopyranose ring through α-(1 → 6) glycosidic bond. The co-existence of α-(1 → 6) and α-(1 → 4) glycosidic linkages endows distinctive physico-chemical properties to pullulan. It is highly biocompatible, non-toxic and non-carcinogenic in nature. It is extremely resistant to any mutagenicity or immunogenicity. The unique properties of pullulan make it a potent candidate for biomedical applications viz. drug delivery, gene delivery, tissue engineering, molecular chaperon, plasma expander, vaccination, etc. This review highlights the potential of pullulan in biomedical research and development.

Preparation and evaluation of curcumin grafted hyaluronic acid modified pullulan polymers as a functional wound dressing material

Curcumin grafted hyaluronic acid modified pullulan polymers (Cur-HA-SPu) by chemical conjugation was designed and prepared, and its film may be used to accelerate wound healing and help to fight infection. The synthesis of Cur-HA-SPu polymer was characterized by FT-IR, ¹H NMR and DSC. Cur-HA-SPu film has a higher swelling ratio than that of HA-SPu film. Moreover, the good biocompatibility of Cur-HA-SPu polymer was confirmed by skin irritation, cytotoxicity and hemolysis tests. Compared to Cur, the MTT and proliferation test carried out in L929 cells revealed that Cur-HA-SPu polymer showed no cytotoxicity and enhanced cell proliferation. Cur-HA-SPu polymer exhibited a certain bactericidal activity against E. coli and S. aureus. Furthermore, the materials showed antioxidant activity when DPPH method determined. Wound healing study using wistar rat model demonstrated that Cur-HA-SPu film obtained better wound healing result than that of HA-SPu film or natural healing. The above results suggest that Cur-HA-SPu film is a promising and safety formulation for accelerating skin wound healing.

Smart drug delivery system activated by specific biomolecules

Essentially, the human body can release in different disease conditions specific biomolecules such as histamines when the body encounters a toxic substance, antibodies which are part of the body's natural immune response or nitric oxide as a cardiovascular signalling molecule. Design and development of "intelligent" delivery systems able to release the therapeutic agent only in the presence of bioactive compounds was presented here. Poly(N-isopropylacrylamide-co-N-(3-aminopropyl)methacrylamide)) (poly(NIPAAm-co-APM)) was synthesized as an exciting pH/temperature sensitive copolymer. Under physiological conditions (pH = 7.4), the APM in copolymer is in the ionized state (pK_a = 8.7), highly hydrophilic and therefore the copolymer loses thermosensitive properties. Remarkably, after electrostatic interactions of APM with specific biomolecules, the copolymer restores the thermosensitive property. Thus, the microgels synthesized from this copolymer are in the "inactivated" state at normal physiological pH and temperature (pH = 7.4 and T = 36 °C). In the presence of specific biomolecules, microgels undergo "activation", shrink and expel mechanically a certain amount of drug. It must be mentioned that the pH-sensitive component plays the role of a biosensor, the biomolecule acts as a triggering agent, and the poly(NIPAAm) represents the delivery component (actuator). MTT tests showed that poly(NIPAAm-co-APM) microspheres are completely devoid of toxicity; moreover, the rabbit dermal fibroblasts vastly adhere to the surface of microspheres.

Pullulan/Poly(Vinyl Alcohol) Composite Hydrogels for Adipose Tissue Engineering

Composite hydrogels based on pullulan (HP) and poly(vinyl alcohol) (PVA) were both prepared by simple chemical crosslinking with sodium trimethaphosphate (STMP) or by dual crosslinking (simultaneously chemical crosslinking with STMP and physical crosslinking by freeze-thaw technique). The resulting hydrogels and cryogels were designed for tissue engineering applications. PVA, with two different molecular weights (47,000 and 125,000 g/mol; PVA₄₇ and PVA₁₂₅, respectively), as well as different P/PVA weight ratios were tested. The physico-chemical characterization of the hydrogels was performed by FTIR spectroscopy and scanning electron microscopy (SEM). The swelling kinetics, dissolution behavior, and degradation profiles in simulated physiological conditions (phosphate buffer at pH 7.4) were investigated. Pullulan concentration and the crosslinking method had significant effects on the pore size, swelling ratio, and degradation profiles. Cryogels exhibit lower swelling capacities than the conventional hydrogels but have better stability against hydrolitic degradation. Biocompatibility of the hydrogels was also investigated by both MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) and LDH (lactaten dehydrogenase) assay. The MTT and LDH assays proved that dual crosslinked HP/PVA₁₂₅ (75:25, w/w) scaffolds are more biocompatible and promote to a greater extent the adhesion and proliferation of L929 murine fibroblast cells than chemically crosslinked HP/PVA₄₇ (50/50, w/w) scaffolds. Moreover, the HP/PVA₁₂₅ cryogel had the best ability for the adipogenic differentiation of cells. The overall results demonstrated that the HP/PVA composite hydrogels or cryogels are suitable biomaterials for tissue engineering applications.

Phytoextraction of Pb and Cu contaminated soil with maize and microencapsulated EDTA

Chelate-assisted phytoextraction using agricultural crops has been widely investigated as a remediation technique for soils contaminated with low mobility potentially toxic elements. Here, we report the use of a controlled-release microencapsulated EDTA (Cap-EDTA) by emulsion solvent evaporation to phytoremediate soil contaminated with Pb and Cu. Incubation experiments were carried out to assess the effect of Cap- and non-microencapsulated EDTA (Ncap-EDTA) on the mobility of soil metals. Results showed EDTA effectively increased the mobility of Pb and Cu in the soil solution and Cap-EDTA application provided lower and more constant water-soluble concentrations of Pb and Cu in comparison with. Phytotoxicity may be alleviated and plant uptake of Pb and Cu may be increased after the incorporation of Cap-EDTA. In addition phytoextraction efficiencies of maize after Cap- and Ncap-EDTA application were tested in a pot experiment. Maize shoot concentrations of Pb and Cu were lower with Cap-EDTA application than with Ncap-EDTA. However, shoot dry weight was significantly higher with Cap-EDTA application. Consequently, the Pb and Cu phytoextraction potential of maize significantly increased with Cap-EDTA application compared with the control and Ncap-EDTA application.