Preparation And Local Analgesic Effect Of The Near-infrared Response Of Ropivacaine Liposomal Temperature-sensitive Gel

Pain is a common complaint after surgery,and local anesthetics are an effective adjunct method for the treatment of postoperative pain.Ropivacaine（Rop）,as an amide anesthetic drug,has been shown to be safer in the central nervous system and cardiovascular system than other drugs,but it still has the limitations of short half-life and large toxic side effects when used as monotherapy.Therefore,it is necessary to design a new delivery system for Rop so that it can be released in the required time and position,enhance the therapeutic effect and reduce toxic and side effects.When a specific wavelength of light irradiates the photosensitive liposome at a specific site,¹O₂produced by photosensitizer acts on ROS-sensitive unsaturated phospholipids,thus realizing controlled release of drugs,and the photosensitive liposomes have good biocompatibility.As an injectable material,in-situ gel can hold its encapsulated particles in place,controlling the interaction between the particles and surrounding tissues,reduce the side effects caused by drug overdose,prolong the action time,and enhance the therapeutic effect.Therefore,both of them are suitable for the research of new Rop delivery systemIn this study,we designed and prepared reactive oxygen species（ROS）responsive liposomes（Lip）containing photosensitizers Pd PC（OBu）₈ and Rop,which was coated with chitosan（CS）andβ-sodium glycerophosphate（β-GP）to form liposome hydrogel（Lip/Gel）.Subsequently,under near-infrared（NIR）irradiation,the photosensitizer produces ¹O₂,which oxidizes or cleaves the unsaturated phospholipids,thus efficiently and accurately controlling the release of Rop in time and space.The research is divided into the following parts:1.Establishment of Rop analysis method in vitroA vitro analysis method for Rop was established to determine the best detection conditions of high performance liquid chromatography（HPLC）,and the specificity,accuracy and precision of the method were proved to be good.2.Preparation and evaluation of NIR-triggered ROS response LipUsing ethanol injection method,ROS-responsive liposomes encapsulating Pd PC（OBu）₈ and Rop were prepared.The optimal prescription was determined by the experiments of Lip particle size,PDI,encapsulation rate and NIR responsiveness.At this time,the particle size of Lip was 193.7±3.07 nm,the PDI was 0.157±0.02,the drug encapsulation rate was 94.62±1.1%,and the shape was smooth and intact without adhesion under the scanning electron microscope.The NIR response study verified the ROS response characteristics of liposomes.Stability experiments proved that liposomes had good stability in PBS medium at 4°C and 37°C for 48 hours.3.Preparation and evaluation of NIR response Rop liposome in situ gelCS andβ-GP were used as matrix to encapsulate Rop liposomes.The optimal formulation of Lip/Gel was obtained by screening the gel time,p H,gel state and encapsulation rate.In the Lip/Gel matrix,Lip is still the main carrier of Rop,and the particle size and shape of Rop has not changed significantly.The vitro release results prove that the Lip/Gel system has a significant slow-release effect and NIR can trigger drug release.Stability experiments show that the Lip/Gel system is stable.In cytotoxicity experiments,Lip/Gel can significantly reduce the toxicity of Rop in PC12cells and C2C12 cells,and NIR will not affect cell proliferation.4.The study of NIR response Rop liposome in situ gel in local analgesiaFirst,the release of fluorescent dyes in animals under NIR irradiation is studied:compared with free dyes and Lip,the fluorescence intensity of Lip/Gel is more concentrated,which proves that Gel is in-situ.The Lip/Gel composite drug delivery system can be retained in vivo for 10 days,proving that it has good biodegradability.In the study of the effect of local analgesia in vivo,the results showed that the sensory block of the Lip/Gel+NIR group was significantly prolonged than that of the other groups,but the changes in motor block were not obvious.Finally,in the biocompatibility evaluation,the results showed that none of the groups caused serious damage and toxicity to muscles and nerves.In summary,the NIR-responsive Rop composite drug delivery system constructed in this paper can effectively solve the shortcomings of traditional local anesthetic injections,reduce the toxic and side effects of Rop,and provide a basis for the light-responsive delivery system of analgesic drugs.