| In recent years,the incidence of eye diseases is becoming higher and higher with the factors such as excessive eye,aging population,environmental deterioration and other factors.Glaucoma,keratitis,conjunctivitis and other eye diseases,such as not timely and effective treatment will eventually lead to recurrent seizures and even serious consequences of blindness.It has a broad application prospect to prolong the retention time and improve the bioavailability of eye.The eye is isolated from other parts of the body,and the immediate instillation and administration of the anterior segment is the most common mode of administration.The physiological structure of the eye and the physical and chemical properties of the drug limit the penetration of the drug through the cornea,making the pre corneal half life short,low bioavailability.How to prolong the retention time of the drug in the cornea and improve the bioavailability of the drug is the hotspot and difficulty in the study of ocular drug delivery.The clinical application of baicalin ophthalmic preparation is mainly used in the treatment of conjunctivitis,keratitis and trachoma.In order to meet the needs of traditional baicalin efficacy,ophthalmic preparation or clinical treatment of ocular anterior segment disease,through increase the drug concentration or the frequency of administration and other ways to improve,but there are still a small amount of drug absorption,greatly limits the application of clinical medicine.The lipid carrier has the advantages of reducing vascular irritation and inflammatory response and prolonging the time of drug action.In vivo lipid emulsion has a certain passive targeting,and can enhance the therapeutic effect of the drug as the carrier of insoluble drugs.In this study,the insoluble and unstable Chinese traditional medicine baicalin was contained in the oil phase of the lipid emulsion,in order to increase the drug loading and improve the physical stability.As an important auxiliary material of lipid emulsion,phospholipids have a significant effect on the quality of lipid emulsion.Study selection of biocompatibility good preparation of baicalin phospholipid as carrier of lipid emulsion eye drops,eye drops after administration in the form of "drug-ocular surface tear film lipid droplet,power protection drugs continued to pass corneal cells,extend the efficacy to the local sustained-release effect.Use eye advantage to play.This study based on the research of the solubility and stability of baicalin,prepared with lipid emulsion as the carrier of the baicalin eye drops to submicroemulsion not containing lipid material as control group,compared the different carrier of Baicalin in vitro corneal permeability,intraocular tissue distribution and elimination kinetics and anterior segment aqueous pharmacokinetics and other content,while the Labrasol and Transcutol model P enhancers of Baicalin in different carrier in vitro corneal makes a beneficial exploration in the eye of the effect,through the application feasibility of microdialysis probe,the main contents are as follows:1.Study on physical and chemical properties of baicalin?Solubility studyThe baicalin solubility and octanol water partition coefficient of 34? was determined by the saturated solubility method,equilibrium solubility of Baicalin in water was 138 + 2.8 g,mL-1 pH in the 2 to 7.4 range,baicalin solubility increases with the increase of pH,a maximum solubility of weak acid.In the water by adding different types of emulsifier can improve the solubility of the drug,which Cremophor EL solubilization effect is most obvious,than water solution increased approximately 3 times for different types of emulsifier between the increase of drug solubility is not obvious.The lipid water partition coefficient is one of the main factors affecting the transport rate and transport rate of baicalin.The Lg P of Baicalin in different pH buffer is<1,and the change of pH does not change its lipophilicity.?Stability studyUse the mapping method,measured at different temperature and light intensity and Linger solution hydrolysis reaction order,reaction rate constant,activation energy of baicalin,baicalin,45001x results show that in the direct light and dark conditions,with the increase of light,the degradation rate also increased.At different temperatures the reaction is first order degradation rate,with the increase of temperature,the degradation trend more obvious,according to Arrhenius equation,linear extrapolation to 25 ?,the baicalin loss of 10%the time required for 13.3 H(t0.9).The degradation of Baicalin in Linger solution was not in accordance with the zero,first,two and three reaction models.Based on the mechanism of Baicalin on degradation of acid,alkaline and alkaline conditions by the line of inquiry,the results show that the stability of baicalin,when more than 3 pH began to downgrade,therefore without considering other factors,the preparation for pH is 3?4 in order to ensure the stability of in the process of baicalin.UV-Vis method was used to determine the content of Baicalin in solubility and stability.The method is simple,accurate and sensitive.It can be used as one of the common methods for the determination of Baicalin in HPLC.2.Preparation of baicalin eye drops with lipid emulsion as carrier?Preparation of lipid emulsion eye dropsThe factors affecting the stability,particle size distribution,drug loading and encapsulation efficiency were investigated by single factor analysis.In the end,the preparation of baicalin lipidty emulsion eye drops was made by using soybean oil,Poloxamer 188,glycerol,which had good biocompatibility and low irritation.The content of Baicalin in the preparation of the eye drops was 1.31±0.01 mg · mL-1,PDI,particle size and zeta potential were 107.3 ± 4.39 nn,PDI 0.089 ± 0.044 and-(26.29 ±1.65)mV.?Characterization of lipid emulsion eye dropsIn order to study the addition of the lipid material in the prescription,the O/W emulsion was prepared by the experimental study.In this experiment,two kinds of lipid free emulsion were prepared.In appearance,properties,drug loading capacity,particle size distribution and stability as index,using transmission electron microscopy,nano particle size/zeta potential analyzer method for two kinds of formulations were characterized.The results show that the preparation method produced by lipid emulsion drops appearance yellow,the surface is free of oil,placed without wall sticking phenomenon;with appropriate amount of diluted water drops in the light blue milk.The distribution of the overall morphology,droplet and aggregation by transmission electron microscopy of two were observed,the results show that the particle size distribution is more uniform,no obvious adhesion phenomenon,lipid emulsion prepared eyedrops emulsion is similar to the shell structure of the baicalin drug loading.Inspect the stability with bright light and high temperature damage conditions on baicalin sub microemulsion system,the results show that the 4 ? sample for 9 months,the results showed that the change of little significance O/W submicron emulsion stability of baicalin,baicalin,and the content of lipid emulsion drops in diameter had no significant change.3.Evaluation of corneal permeabilityThe amphiphilic properties of phospholipids can increase the corneal permeability of the drug through the barrier of water soluble substances and lipid soluble substances.But the effects of drugs through the cornea and formulation and preparation factors,also available for absorption and corneal thickness and area,through the pores of drug related physiological factors,but also with the prescription of enhancers and the type and amount of related.In this study,the effects of penetration enhancers on corneal permeability were studied on the basis of lipid emulsion.?The effect of new penetration enhancers on corneal permeabilityThe effects of Labrasol and Transcutol P two penetration enhancers on the corneal permeability of different formulations were studied by using Franz aqueous solution as the control.The results show that the solubility of Baicalin in Transcutol P is better than Labrasol,directly into the Labrasol and in the water,water more than 83%,in the process of experiments show that Labrasol has on corneal epithelial cells and endothelial cells damage.With the increase of the concentration of Transcutol P,the apparent permeation coefficient of baicalin showed an increasing trend in the aqueous solution,but not in the submicron emulsion.?Evaluation of corneal permeability in vitroThe permeation and in vitro release models of different formulations were fitted by in vitro corneal method.The results showed that Transcutol P had no obvious effect on the apparent permeability coefficient of Baicalin O/W submicron emulsion eye drops and baicalin lipid emulsion drops.When the concentration of Labrasol was low,baicalin apparent permeability coefficient increased with the concentration of Labrasol increased when the Labrasol excess,baicalin apparent permeability coefficient increased with Labrasol concentration and no increase,balance.The results of in vitro release showed that baicalin was close to the first order release equation in the O/W type microemulsion eye drops,and the release of baicalin was closer to Higuchi and Riger-Peppas equation in the lipid emulsion eye drops.In the last step,the distribution of Baicalin in submicron emulsions can be changed.4.Intraocular distribution and irritation evaluation?Distribution of different preparations in the eyeIn order to study the distribution of Baicalin in different tissues of the eye,the rabbits were isolated and the tissues were separated.The results showed that baicalin O/W submicroemulsion eyedrops and baicalin emulsion drops of baicalin can significantly prolong the circulation time in the eye,in addition to improve the drug concentration in the lens outside of the organization,concentration of submicroemulsion group eyedrops and Intralipid group eyedrops were 26.2 times water drops and 7.8 times in 0.5h when the drug distribution of the cornea were 16.67 times and 7.37 times.In the 8h group,the amount of drug retention in the eyes of the lipid emulsion eye drops group was(1.365 +.0.102)?g·g-1,which was increased by a factor of 8.32 compared with that of the submicron emulsion group,which was equal to the highest concentration of the aqueous solution of eye drops(g).In the posterior segment vitreous body tissue,lipid emulsion group highest drug retention by the concentration of aqueous solution in the 0.5h group(0.412 + 0.021)?g·g-1,delayed to 2H(2.337 + 0.238)?g·g-1,but in the Intralipid group and failed to extend the release time.The experimental results also showed that no significant improvement was observed in the distribution of the drugs in the posterior segment of the lens in either the submicron emulsion group or the lipid emulsion group.?In vivo stimulation evaluationThe Ringer lactate solution as control,using the homobody control method of different formulations of eye irritation evaluation.The results show that the submicroemulsion group or Intralipid group by drip experiment to stimulate the eye eye after administration,according to the Draize eye irritation assessment standard,no irritation,no change in the cornea,conjunctiva and iris ciliary body,the preparation of eye irritation.5.Pharmacokinetics evaluation?Tear elimination kineticsThe method was used to evaluate the kinetics of the elimination of Baicalin in the anterior segment of the eye.The results showed that the concentration of Baicalin in different tissues of the eye varied with time.Compared with emulsifier free aqueous solution eyedrops group,the presence of emulsifier can make the drug faster concentration in the tissues,and the presence of lipid material can significantly improve the absorption capacity of corneal drug.The drug in the cornea.Drug concentration by retention of emulsifier free aqueous solution in the group by(0.135 + 0.017)?g·g-1 to contain emulsifier O/W submicroemulsion eyedrops group(0.995 + 0.045))?g·g-1,and the lipid in milk up to(2.251 + 0.020)?g·g-1.Obviously,to prescription drugs in the system determines the absorption of the drug,preparation of submicron emulsion of baicalin increased corneal absorption rate slowed down but the carrier material containing lipid material can make the drug release,to extend the efficacy of sustained release effect.Combined with the amount of drug in the sclera,it can be confirmed that the release of O/W submicron emulsion group and lipid emulsion group showed a sudden release effect in the range of 0 to 2h,and the drug concentration showed a slow downward trend with time.The transcellular transport mode and lipid emulsion,and lipid containing material system is critically dependent on clathrin mediated endocytosis of the complete transport,and in the presence of O/W emulsifier submicroemulsion by passive diffusion transport mode.Lipid emulsion and O/W submicroemulsion composition contained in the main difference in the phospholipid,the composition is one of the main components of the tear,after the eye drops can blend well with the tear,and can reduce the amount of surfactant submicroemulsion,increased corneal penetration volume reduced eye irritation,but the toxic reaction and need further research.?Pharmacokinetics in aqueous humorStudy on the pharmacokinetics of different dosage forms in aqueous humor by corneal puncture.The results showed that baicalin submicroemulsion,lipid emulsion can improve corneal retention,reduce anterior segment tear on the drug dilution,compared with aqueous solution,submicroemulsion AUC increased 5.89 times,compared with lipid emulsion AUC submicroemulsion increased 2.92 times.Compared with MRT solution,submicroemulsion increased nearly 1.05 times more lipid milk submicroemulsion was 1.18 times higher than that of baicalin emulsion preparation,improve drug in biological adhesion,corneal and lipid droplet as well as drug to corneal transfer provides power.The results of pharmacokinetics in aqueous humor showed that sub microemulsion and lipid emulsion changed the intraocular pharmacokinetics of aqueous solution,and t1/2 submicron emulsion and lipid emulsion increased by nearly 3 times compared with that in aqueous solution.?Exploration on the application of microdialysis in the ocularTo explore the feasibility of microdialysis sampling technique in the determination of drug concentration in the eye,through the investigation of effect of needle type,probe recovery perfusion fluid components,perfusion fluid velocity,concentration,temperature and other factors around.Different factors change although the method recovery was not improved,but the recovery in the results for baicalin low permeability composition rate determination and pharmacokinetic studies provide experimental basis,to provide reference for the recovery of drug and other properties of the rate of improvement.The formulation factors of Baicalin submicroemulsion preparation process study,screening,preparation characterization,stability,ocular irritation study,eye tissue distribution,anterior segment tear elimination,pharmacokinetics in aqueous humor research shows that the lipid emulsion as the carrier of baicalin eye drops for eye treatment.Lipid milk as an ocular drug delivery carrier has the following advantages:(1)can increase the solubility of poorly soluble drugs,drug loading can improve oil and water insoluble drugs;(2)using biocompatible materials preparation,good safety,no irritation;(3)to the lipid emulsion as a model drug carrier baicalin,can increase the physical stability of the drug;(4)can prolong the residence time of drugs in the eye,change the drug in vivo tissue distribution and pharmacokinetic properties,there may be further development of targeted agents,to provide new ideas for development of poorly water-soluble drug ophthalmic drug delivery system. |
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