| Supramolecular gels are a fascinating class of soft materials, formed by the self-assembly of low-molecular weight gelators through non-covalent bond interactions. The non-covalent interactions include hydrogen bonding, ?-? stacking, metal-ligand coordination, electrostatic interaction, etc. The resultant supramolecular gels have a nanoscale three-dimensional network. The non-covalent nature of these supramolecular hydrogels confers them with the thermo-reversibility and the inherent ability responding to external stimuli, which endows a broad spectrum of applications in the fields of biomedical functional materials, such as drug carriers, tissue engineering and biosensing. However, because of non-covalent interactions and a large quantity of solvent in the system, there exists an inherent defect of lacking mechanical strength, which greatly restricts their application, especially as a drug carrier. This defect makes supramolecular gels susceptible to damage and difficult to achieve drug stable loading and sustained release. Therefore, it is still a great challenge to improve the mechanical strength of supramolecular gels in the field of supramolecular materials.In recent years, the hybridized supramolecular gels can be prepared by the incorporation of polymers, organic/inorganic nanoparticles as well as the supramolecular co-assembly. The resultant hybridized supramolecular gels can not only greatly improve the mechanical strength, but also lead to several unexpected structural/functional features, which greatly expands their application prospect in drug delivery and tissue engineering. However, hybridized supramolecular gels are complex systems. Taking into account of the structural characteristics of gelators and the condition of self-assembly, it is difficult to prepare hybridized supramolecular gels both with outstanding structural and functional properties through direct mixing method. This results in need of reasonable design and modifying the structure of gelators and additives, as well as the cumbersome steps to gain ideal results. Furthermore, controllable drug release from supramolecular gels is generally modulated by pH and temperature. So far. other control measures, such as the biological macromolecules. electric-driven release, light controllable release are still rare.Based on the theory of supramolecular self-assembly and the idea of hybridization, the microemulsions became a gel state due to the supramolecular self-assembly of the gelator in the oil phase. The resultant microemulsion supramolecular gels not only had outstanding mechanical properties but also realized a hydrophilic/lipophilic dual-drug loading and protein-modulated release utilizing hydrophilic and hydrophobic properties of microemulsion. Moreover, based on the mechanism of supermolecular fiber-reinforced polymers, conductive polymer hydrogels reinforced by supramolecular structure were prepared and the electric-driven release of model drug from reinforced hydrogels was investigated. Furthermore, combining polymer network structure with supramolecular network structure, the resultant hybridized supramolecular gels were used for light controllable drug release.This thesis is consisted of several sections as the following:1) Microemulsions were prepared by using Tween 80 as a surfactant,1,2-propylene glycol as a co-surfactant, isopropyl myristate as an oil phase and phosphate-buffered saline as an aqueous phase. The resultant microemulsions possess a bicontinuous phase structure which was characterized by pseudo-ternary phase diagrams, POM and dye solubility tests. The microemulsions were gelled by the self-assembly of sorbitol derivatives (DBS) as a gelator to form microemulsion supramolecular gels. Ball falling method and differential scanning calorimetry (DSC) showed that microemulsion supramolecular gels have good thermal stability. POM images indicated that microemulsion supramolecular gels have the typical characteristics of sphaerocrystal. SEM images revealed that microemulsion supramolecular gels have a three-dimensional network. Rheological studies confirmed that microemulsion supramolecular gels have good mechanical properties, the storage modulus is 105 Pa. Compared with the supramolecular gels, the storage modulus increases two orders of magnitude.2) Using bicontinuous phase structure of microemulsions, microemulsion supramolecular gels were used as the carrier for lipophilic curcumin (Cur)/hydrophilic 5-aminosalicylic acid (5-ASA) dual-drug. Spontaneous diffusion and protein-modulated release behavior of dual-drug molecules were investigated. Spontaneous diffusion of both drugs from the microemulsion supramolecular gels showed that the release behavior of both drugs are significantly influenced by the concentration of the gelator DBS, temperature and pH, but less affected by ionic strength. This may be because the impact on DBS intermolecular interactions caused by environmental changes. The BSA modulated release of both drugs from the microemulsion supramolecular gels was found to be pH dependent. Under neutral condition (pH 7.4), BSA inhibits the drug release, but promotes the drug release under acidic conditions. Constructing the microemulsion supramolecular gels may provide a new strategy and application prospect for a safe and effective controllable release of the hydrophilic/hydrophobic dual-drug.3) Due to the very poor mechanical strength of polyaniline-poly(styrene sulfonate) (PANI-PSS) conducting hydrogels, we explored the possibility to improve the strength of PANI-PSS hydrogels using supramolecular nanofibers formed by self-assembly of sorbitol derivatives (DBS). The compressive strength of these reinforced hydrogels was found to be 11 times higher than that of the unreinforced one. SEM studies indicated that the in-situ formed DBS nanofibers and PANI-PSS chains are entangled, leading to improvement of the hydrogel strength. The conductivity of reinforced hydrogels measured by impedance was found to be 10"4 S/cm, rather similar to that of the unreinforced hydrogels. In addition, the spectra of cyclic voltammetry for the reinforced and unreinforced hydrogels were almost the same. These results reveal that the presence of DBS nanofibers does not affect the electric properties of PANI-PSS hydrogels. As drug carriers with electric-driven release, the release rate of model drug Rhodamine B (RhB) from reinforced PANI-PSS hydrogels significantly increased with the increase of applied voltage. Furthermore, when the voltage was alternatively applied, a pulse release could be realized. The conducting hydrogels realize the pulse release of drugs, has an important significance to exploit novel actuators and tissue engineering scaffold materials.4) Glutathione-Ag (GSH-Ag) supramolecular hydrogels have almost no mechanical strength and the disassembly of GSH-Ag complexes occurs very easily under UV irradiation, low molecular weight polyvinyl alcohol (PVA) was used to reinforce GSH-Ag gels. The phase transition temperature of GSH-Ag gels can be increased from 45 to 60? in the presence of only 0.8 wt%of PVA. Rheological studies indicated that the storage modulus of reinforced GSH-Ag gels was 5 times higher than that of unreinforced gels. SEM studies revealed that the macromolecular chains of PVA are intertwined with the GSH-Ag aggregates, leading to an increase of mechanical strength. TEM studies and UV-Vis spectra indicated that Ag+within the GSH-Ag gels was in-situ reduced to form Ag nanoparticles under the UV irradiation. Meanwhile, gradual disassembly of GSH-Ag hydrogels can be induced through controlling the time of UV irradiation. Based on this feature, a controllable release of a loaded model drug (crystal violet, CV) and Ag species can be realized from the reinforced GSH-Ag gels. In addition, the controllable release behavior of CV could be effectively modulated by pH of the release medium, temperature, drug loading and the concentration of GSH-Ag. The release media show a good inhibition effect on E. coli. and S. aureus. The gradual disassembly of supramolecular hydrogels can be induced through UV irradiation to achieve a sustained release of drug and bacteriostatic agent, has the potential to be the novel drug carriers and medical antibacterial materials. |
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