Preparation And Application Of Temperature-sensitive Gel Of Total Flavonoids From Platycladus Orientalis Leaves

The Platycladus orientalis leaves have a long history of treating alopecia.As early as the"Compendium of Materia Medica",it was recorded that"it has the effect of promoting hair growth".Modern research has shown that the main active ingredient of Platycladus orientalis leaves is total flavonoids（POF）,but Its low water solubility and low bioavailability limit its efficacy.Traditional Chinese medicine uses platycladus orientalis leaves to treat alopecia mostly in the form of topical tinctures and oral decoctions,which have disadvantages such as short drug retention time,unclear therapeutic doses,and poor patient compliance.In order to solve these problems,this project developed a temperature sensitive gel of POF for skin administration.The POF were embedded in solid lipid nanoparticles（SLN）to improve its solubility and transdermal permeability,and loaded in gel matrix to prolong the drug residence time and increase patient compliance.The therapeutic dose range of POF was determined through pharmacodynamics experiments,which laid a foundation for clinical use.The specific research content is divided into the following parts:Part 1:Preparation of POF-SLNPOF-SLN was prepared by emulsion evaporation-low temperature curing method,and the optimal formulation was determined by single factor investigation and response surface optimization:POF 30mg,drug to lipid ratio 1:11,lecithin 313 mg,Poloxam188100 mg,ethanol 10m L,water 33m L,emulsification temperature 70℃.The obtained SLN has spherical appearance and uniform distribution,average encapsulation rate is79.62%,and particle size is 218.3±13.2 nm.5%dextran was used as lyophilized protective agent to freeze-dried SLN suspension to obtain the lyophilized powder.After redissolution,the average particle size was 272.8±15.7 nm,which was spherical.FTIR,DSC and XRD were used to characterize POF-SLN.The results showed that the chemical properties of the drug did not change,and it existed in the lipid nanoparticles in an amorphous state.In vitro release experiments showed that POF-SLN showed slow drug release characteristics,and the fitting equation was Q=21.425t^1/2+13.161（R~2=0.9469）which was consistent with Higuchi release model.In vitro transdermal experiments showed that the transdermal penetration rate of PHOF-SLN was 23.215μg/cm~2·h,which was 1.57 times higher than that of POF solution.Part 2:preparation of POF temperature sensitive gelPOF temperature sensitive gel was prepared by cold solution method.Taking the gelation temperature as the evaluation index,the optimal formulation concentration（W/V）was obtained by single factor experiment and star point design-response surface optimization method as:methyl cellulose 2.16%,Poloxam407 21.30%,Poloxam1883.54%and glycerol0.5%.Under the conditions of this prescription,the gelation temperature was 32.4℃.When T<32.4℃,the preparation was in a solution state with a small viscosity ranging from 0.133 to 0.401 Pa·s.When T≥32.4℃,the viscosity of the preparation increased sharply to 44.587 Pa·s,presenting a gel state,which could firmly adhere to the head skin.The fitting equation of in vitro release was Q=16.844t^1/2-1.128（R~2=0.9820）,which was consistent with Higuchi model and had a certain sustained release effect.In vitro transdermal experiments showed that the transdermal effect of the preparation was better than that of the bulk drug gel,and it could promote the transdermal absorption of POF.Part 3:Establishment of temperature sensitive gel quality standard for POFAccording to the requirements of Gels in Chinese Pharmacopoeia 2020 edition,quality evaluation and preliminary stability study of POF temperature sensitive gels were conducted.A set of quality detection system was established in accordance with the requirements of pharmacopoeia:the preparation was temperatuent-sensitive.When T≥32℃,its appearance was uniform,fine and milky yellow gel,and when T<32℃,its appearance was milky yellow solution.The gel particle size range is less than 180μm.The p H range is 6.33～6.56.The viscosity range is 0.384-0.423 Pa·s.Stability studies show that the preparation should be kept in a dark,sealed,cool place.Part 4:Pharmacodynamics and safety study of POF gelA rabbit depilation model was established,the hair removal area was 2×2 cm,and1m L was administered daily.Low dose group（0.64 mg/m L）,medium dose group（1.28mg/m L）and high dose group（2.56 mg/m L）were used to investigate the growth promoting effect of the POF gel on hair,and skin irritation tests were carried out to observe the safety of skin medicine.Pharmacodynamic experiments showed that three different doses groups of POF thermosensitive gel had hair growth promoting effect on rabbit hair removal models.The best effect is in the middle-dose group and the high-dose group.The hair growth rate of the two groups was 1.70～1.73 times higher than that of the control group,and the weight of new hair was 1.05～1.06 times higher than that of the control group.The skin irritation test showed that there were no irritant reactions such as edema and erythema in damaged skin and intact skin,indicating that the preparation was safe.In conclusion,POF temperature sensitive gel was prepared for the first time in this subject.It has the characteristics of accurate dose,good stability,safety and effectiveness.It is a potential new preparation for treating alopecia.