Shengmiao Zhang

Macroporous Polymers with Aligned Microporous Walls from Pickering High Internal Phase Emulsions

A novel class of macroporous polymers, open macroporous polymers with aligned microporous void walls, were prepared by combining particle-stabilized high internal phase emulsion (Pickering HIPE) and unidirectional freezing technique. These Pickering HIPEs were prepared by utilizing poly(urethane urea)/(vinyl ester resin) nanoparticles as the sole stabilizer, and this nanoparticles also acted as building blocks for the resulting macroporous polymers. Moreover, the morphology and compression modulus of the resulting porous materials could be tuned easily. This means now Pickering-HIPE templated open-cell foams can be prepared, and this route was normally achieved with surfactant and/or chemical reaction involved.

Chitosan and gelatin based prototype delivery systems for the treatment of oral mucositis: from material to performance in vitro.

In this study we developed and evaluated a prototype of an effective occlusive mucoadhesive system for prophylaxis and/or treatment of oral mucositis based on chitosan and gelatine models together with nystatin as a prophylactic agent incorporated into the formulation and investigated drug release in-vitro. Results of in vitro studies showed that chitosan and gelatine based gels posses properties that makes them excellent candidates for treatment of oral mucositis. These properties include not only the palliative effects of an occlusive dressing but also the potential for delivering therapeutic compounds with chitosan gels providing drug concentrations above their minimum inhibition concentration and extending the retention time in the oral cavity due to their bioadhesive properties. Chitosan also offers an advantage over suspensions because of its inherent antimicrobial properties. The performance of gelatin-based gels highlights the novel, non-toxic, in situ forming gelatine based hydrogel. The results of in vitro drug release experiments demonstrated that all the hydrogel showed sustained release properties.

Towards Development of Novel Chitosan Based Drug Delivery Prototypes: Devices for Targeted Delivery Drug Therapy at the Molecular Level in Aqueous Media

We recently showed that chitosan containing hydrogel isare capable of displaying antioxidant activity and prevents formation of oxidative DNA damage in vitro [9]. In this short communication we report our investigations towards developing two alternative novel simple flexible and effective drug delivery systems that provide optimal dosage of drugs precisely where and when needed and therefore achieve and sustain a complex delivery profile. Two topics of a. free radical generation in biocompatible media and b. supramolecular host-guest recognition through miniaturizing and multi-functionalizing molecular carriers for improved drug delivery in disease-specific manner are combined with the aim of harnessing free radical reactivity within the laboratory and developing alternative and effective treatments for disease states mediated by free radicals.

Bioactive-Functionalized Interpenetrating Network Hydrogel (BIOF-IPN): A Novel Biomaterial Transforming the Mechanism of Bio-Repair, Bio-Adhesion and Therapeutic Capability – An In Vitro Study

The purpose of this investigation was to evaluate and report the in vitro performance of a few selected Bioactive- Functionalized Interpenetrating Network Hydrogels (BIOF-IPN); a novel biomaterial with a build-in mechanism of biorepair capacity, bio-adhesion and therapeutic capability. The study also evaluates the cytotoxicity of the newly developed material, and its ability to be used in the dental field. In this study, four bioactive-functionalized interpenetrating network hydrogels (BIOF-IPN) were prepared by dispersion of different therapeutic agents. The dentin bond strength is tested, the bio-adhesivity, modulus of elasticity and cytotoxicity of the materials were investigated, and the performance of the therapeutic-agents release profile, evaluated. The gels used in this study demonstrated excellent capacity in leading to high internal surface areas with low diffusional resistance. An increase in bond strength of the dentin treated with the BIOF-IPNs compared to the bond strength of the conventionally bonded teeth was indicated, and a significant increase in the modulus of elasticity observed. BIOF-INPs showed high adhesive force promotes binding to the negative surface of skin or dentin structure. It was found that chitosan alone increased the cell survival rate remarkably (113%) and its presence with naproxen and ibuprofen increased the cell survival rate [naproxen (93%), chitosan/naproxen (96.6%), ibuprofen (76.6%), and chitosan/ibuprofen (89.1%). The use of BIOF-IPNs has increased the time of the release of therapeutic agents, and protected the active ingredient from any type of free radical damage produced in and around the active site. Present results demonstrate the capability of the BIOF-IPNs to play an important role in the defense mechanism, and in the functional multidimensional restorative repair materials. The findings suggest that the new material would definitely find applications in functional dental composites and regenerative dentistry.

Insights into Functional Erythromycin/Antioxidant Containing Chitosan Hydrogels as Potential Bio-active Restorative Materials: Structure, Function and Antimicrobial Activity

Substantial data are available in the literature on the role of Reactive Oxygen Opecies (ROS) and antioxidants in disorders such as the inflammatory and in chronic immune mediated conditions such as rheumatoid arthritis. However, remarkably little information is available on the periodontal diseases, which show many of the pathological features of other chronic inflammatory diseases. The periodontal tissues also provide an ideal medium within which to study mechanisms of ROS mediated tissue damage and of antioxidant defense in response to bacterial colonization, through the non-invasive collection of GCF. Bio-adhesive polymers appear to be particularly attractive for the development of alternative etches free dentin bonding system with an added advantage of additional therapeutic delivery systems to improve intradental administration of therapeutic and prophylactic agents if necessary. Chitosan, which is a biologically safe biopolymer, has been proposed as a bio-adhesive polymer and are of continuous interest to us due to their unique properties and flexibility in broad range of oral applications reported by others and us recently. The objectives of this study is to evaluate the novel chitosan based functional drug delivery systems which can be successfully incorporated into “dual action bioactive restorative materials” containing common antibiotic such as erythromycin, krill oil, aloe and aspirin as commonly used antioxidant species. Methods: The novel hydrogels will be investigated with respect to the antioxidant capacity and drug release capacity of the tetracycline as well as erythromycin from the designer drug delivery system, the use of SEM imaging for the characterization of the surfaces and reactive features of novel materials with antimicrobial potential as well asuse of the newly designed materials as an effective adhesive restorative materials. Results: A continuous release of erythromycin, while maintaining antibiotic effects against the tested bacteria,for at least 24 hours was shown from designer chitosan-antioxidant hydrogels. The increase antioxidant capacityof the designer material, significant antimicrobial capacity as well as adhesive dentine bond strength make thechitosan-containing restorative materials suitable and potentially advantageous materials for restorative andperiodontal applications in-vitro. The addition of antioxidants to the functionalized restorative material acts as aalternative free radical defense mechanism and therefor increases the shear bond strength teeth by managing theexcess of free radicals produced during common restorative procedure. Future investigations are necessary tovalidate this hypothesis.

Switchable release and recovery of nanoparticles via a Pickering-emulsion-templated porous carrier

A Pickering-emulsion-templated macroporous polymer was utilized as a novel release carrier for switchable controlled release and recovery of nanoparticles. With silica nanoparticles as stabilizers, oil-in-water Pickering high internal phase emulsions were prepared as templates to synthesize porous poly(N-isopropylacrylamide) materials with silica nanoparticles inlaid in the polymer void walls. The porous materials can effectively avoid the diffusion of silica nanoparticles when the release is undesirable, and can resorb the released nanoparticles back from the aqueous solution simply by controlling the temperature. Because a wide range of functional nanoparticles can be used to stabilize Pickering emulsions, the method developed herein provides an alternative to prepare carriers for controlled release and recovery of functional nanoparticles.

Novel Melatonin-chitosan Hydrogels as Suitable Oral Bio-drug Delivery Systems to Fight Oral Mucositis: Synergy of Antioxidants and Bioactives in Action

Oral mucositis is a consequence of the toxic effects of chemotherapeutic agents and irradiation on oral mucosa cells. It is estimated that oral mucositis is a complication in 40% of patients receiving chemotherapy, more than 90% of those irradiated for head and neck cancer. This condition is frequently associated with severe pain and inflammation and can cause malnutrition, systemic infections, and low quality of life, as well as limiting chemotherapy doses. The pineal hormone melatonin inhibits the production of free radicals that mediate the toxicity of chemotherapy. The main objectives of this study is to develop and evaluate a novel occlusive bioadhesive system for prophylaxis and/or treatment of oral mucositis based on chitosan and melatonin in order to exploit natural biomaterials as functional biocompatible gels and evaluate the performance of the alternative drug delivery system towards in-vitro generated free-radical mediated inflammation response as a model system for oral mucosatis.

Evaluation of Nystatin Containing Chitosan Hydrogels as Potential Dual Action Bio-Active Restorative Materials: in Vitro Approach

Healing is a specific biological process related to the general phenomenon of growth and tissue regeneration and is a process generally affected by several systemic conditions or as detrimental side-effects of chemotherapy- and radiotherapy-induced inflammation of the oral mucosa. The objectives of this study is to evaluate the novel chitosan based functional drug delivery systems, which can be successfully incorporated into “dual action bioactive restorative materials”, capable of inducing in vitro improved wound healing prototype and containing an antibiotic, such as nystatin, krill oil as an antioxidant and hydroxyapatite as a molecular bone scaffold, which is naturally present in bone and is reported to be successfully used in promoting bone integration when implanted as well as promoting healing. The hydrogels were prepared using a protocol as previously reported by us. The physico-chemical features, including surface morphology (SEM), release behaviors, stability of the therapeutic agent-antioxidant-chitosan, were measured and compared to the earlier reported chitosan-antioxidant containing hydrogels. Structural investigations of the reactive surface of the hydrogel are reported. Release of nystatin was investigated for all newly prepared hydrogels. Bio-adhesive studies were performed in order to assess the suitability of these designer materials. Free radical defense capacity of the biomaterials was evaluated using established in vitro model. The bio-adhesive capacity of the materials in the in vitro system was tested and quantified. It was found that the favorable synergistic effect of free radical built-in defense mechanism of the new functional materials increased sustainable bio-adhesion and therefore acted as a functional multi-dimensional restorative material with potential application in wound healing in vitro.

Insights into functional tea infused-chitosan hydrogels as potential bio-active restorative materials

Introduction: We described novel chitosan hydrogels (chitosan-H) containing tea infusions (green, red and black) as functional additive prototypes with special focus on the design and functionality of dual action composite restorative materials. Their intended uses include remineralizing bases/liners, therapeutically active restorative materials and/or functional additives as well as functional prototype of the drug delivery system. Materials and Methods: The above mentioned hydrogels were prepared by dispersion of the corresponding component in glycerol and acetic acid with the addition of chitosan gelling agent. The surface morphology scanning electron microscope (SEM), release behavior (physiological pH as well as acidic conditions), stability of the hydrogels as well as antioxidant capacity of the tea infused hydrogels was evaluated. Results: It was found that all the anti-oxidant chitosan-H hydrogels treated dentine gave significantly (P < 0.05; Non-parametric ANOVA test) higher shear bond strength values than dentine treated or not treated with phosphoric acid. Overall, there was a small relapse in the shear bond strength after 6 months. The SEM is employed to observe the surface of the newly made functional restorative materials. The anti-oxidant capacity of various black, red and green tea infusions was investigated and demonstrated increased antioxidant stability of the newly prepared material stability. Conclusion: We have developed and evaluated several functional chitosan hydrogels with several targets as therapeutic restorative materials, the added benefits of their unique functionality involve increased dentin adhesive bond strengths (after 24 h and after 6 month), concept of using functional materials as carriers for pro-drugs as well as display certain degree of defense mechanism for a free radical damage.

Vinyl ester oligomer crosslinked porous polymers prepared via surfactant-free high internal phase emulsions

Using vinyl ester resin (VER) containing styrene (or methyl methacrylate) and vinyl ester oligomer (VEO) as external phase, Pickering high internal phase emulsions (Pickering HIPEs) having internal phase volume fraction of up to 95 vol% were prepared with copolymer particles as sole stabilizer. Polymerizing the external phase of these Pickering HIPEs led to porous polymers (poly-Pickering-HIPEs). Compared to the polystyrene- (PS-) based poly-Pickering-HIPEs which were prepared with mixture of styrene and divinylbenzene (DVB) as crosslinker, the poly-Pickering-HIPEs herein showed much higher elastic modulus and toughness. The elastic modulus of these poly-Pickering-HIPEs increased with increasing the VEO concentration in the external phase, while it decreased with increasing internal phase volume fraction. Increasing VEO concentration in the external phase also resulted in a decrease in the average void diameter as well as a narrow void diameter distribution of the resulting poly-Pickering-HIPEs. In addition, there were many small pores in the voids surface caused by the volume contraction of VER during the polymerization, which suggests a new method to fabricate porous polymers having a well-defined hierarchical pore structure.