Preparation And Controlled Release Properties Of Stimulus-responsive Carriers Based On Liquid Crystal Materials

Drug delivery systems are of great significance for biomedicine because of their ability to release active drug components to achieve the desired therapeutic effects.As a new intelligent system,drug delivery systems are capable of physically or chemically loading drug components onto small molecule or polymeric carriers that can respond to different stimulus(e.g.,temperature,pH,enzymes,etc.),and transporting precise doses of drugs continuously to the exact target site at the expected controlled rate.It is essential for effective and safe therapeutic strategies.The unique characteristics of liquid crystal materials,such as their responsiveness to external stimuli like temperature,electricity,and magnetism,make them highly suitable for use in the controlled release of drugs.Their self-assembled structures are particularly adept at quickly and accurately responding to external stimuli.Lyotropic liquid crystals are the primary focus of current research in the field of drug delivery,while the use of thermotropic liquid crystals has yet to be explored.Due to the above backgrounds,this paper presents three distinct forms of liquid crystal microcapsules,composite hydrogels and liquid crystal elastomers,all of which are derived from liquid crystal materials.These smart carriers are constructed by functionalizing liquid crystal microcapsules,functionalizing liquid crystal matrix,and co-functionalizing microcapsules and matrix,and are capable of responding to external stimuli.Detailed investigations into the structure,morphology,responsiveness to stimuli,and controlled release characteristics of these carriers have revealed the potential of liquid crystal materials in drug delivery systems.The main research of this paper consists of three aspects:(1)A cholesteric liquid crystal microcapsule with new stimulus response mode and stimulus response core was designed.In the new design,the molecular motor acts as an opto mechanical stirrer,which can magnify the rotational motion at the molecular level into the macroscopic change of cholesteric liquid crystal under ultraviolet radiation.The research on its light response and drug release mechanism shows that the rearrangement of liquid crystal molecules caused by the unidirectional rotation of the molecular motor under UV intensifies the thermal movement of drug molecules.At the same time,due to the synergistic effect with the photothermal effect,the drug will be forced to accelerate through the microcapsule shell to promote the drug release.In addition,this sustained and controlled release system not only has a broad spectrum of drugs,but also can achieve the controlled and on-demand release of drugs by controlling the concentration and chiral size of the molecular motor.(2)This paper presents a smart composite carrier with multiple stimuli responses,which is based on natural polymer sodium alginate and functionalized with NIPAm and AA as functional monomers.Furthermore,the cholesteric liquid crystal microcapsules endow it with ultraviolet light responsiveness,while PDA nanoparticles provide near-infrared light responsiveness.This research is novel in that it focuses on the dynamic regulation of multiple response behavior,which is an area that has not been extensively studied.The intelligent composite carrier has remarkable mechanical and swelling properties,and is capable of responding quickly and reversibly to stimuli.Research has revealed that it can be used in four conditions:temperature,pH,UV light and NIR light.It also is able to provide controlled release performance when stimulated,allowing for convenient and rapid on-demand and intelligent drug delivery.(3)This study seeks to utilize anisotropic functionalized liquid crystal polymer matrix for drug sustained and controlled release system,thereby widening the range of liquid crystal materials in the biomedical field.A "sponge-like" porous liquid crystal film that is responsive to UV light has been designed and prepared for this purpose.The formation of a liquid crystal polymer network through the covalent cross-linking of anisotropic liquid crystal molecules and azobenzene functional molecules results in the macroscopic deformation of the liquid crystal film when exposed to ultraviolet light.This provides the impetus for the release of drugs.And The study revealed that the porous liquid crystal film was able to effectively facilitate the release of drugs when exposed to pulsed ultraviolet light.Moreover,it was found to possess a continuous response to ultraviolet light,thus demonstrating its potential in the field of drug delivery.