Chitosan-g-PAA Hydrogels for Colon-Specific Drug Delivery: Preparation, Swelling Behavior and in vitro Degradability

A series of cross-linked hydrogels for colon-specific drug delivery were synthesized by graft copolymerization of Chitosan and acrylic acid using N, N＇-methylene-bis-（acrylamide） as a cross-linker. Their swelling behavior in different pH buffer solutions and colonic enzymatic degradability were studied. The obtained results show that these hydrogels have good pH sensitivity which can avoid drug release in stomach, and their swelling kinetics in stimulant intestinal environment follow second-order swelling kinetics equation. The factors influencing the swelling kinetics include the degree of cross-linking and the composition, which may control no release or a little amount release of drug inside the hydrogels in the small intestine by tailoring these factors. The gels are degradable by colonic enzymes and there is a correlativity between the degradation of networks and the swelling degree of the gels, which may trigger the release of drug in the colon. The hydrogels show a great potential for their application in oral colon-specific drug delivery system.

Influence of coating on the triamcinolone release of alginate chitosan beads for colonic drug delivery

The aim of this study was to evaluate the effect of coating of alginate-chitosan (AL:CS) beads on the colonic drug delivery. The AL:CS systems containing triamcinolone (TC) were coated with the HPMCP and Eudragit? L100 by immersion and by spraying methods. The drug release profile in simulated colonic medium was determined using 5% human fecal content suspension in 0.01 N buffer solution, pH 6.8. The systems coated with HPMCP showed a lower rate of drug delivery in simulated enteric medium. The delivery profile in simulated colonic medium followed zero-order kinetic. The coated systems provided a promising drug-delivery profile for application in colonic drug delivery.

Strategies and opportunities of micro/nano delivery systems for targeted therapy of ulcerative colitis:Focus on underlying mechanisms and future perspectives

Ulcerative colitis(UC)is a common progressive inflammatory disease whose incidence has increased rapidly in recent years,and can develop into colorectal cancer in severe cases.There are currently no adequate or effective treatments for UC due to the fact that some patients have found suboptimal results after repeated administration,while others have experienced adverse effects.With the rapid development of nanotechnology,developing innovative colon-targeting platforms is essential to improving efficacy,reducing side effects,and improving patient compliance.In this review,we summarize the pathophysiological characteristics of UC and the most recent status of numerous nanodrug delivery systems based on different targeting mechanisms in treating UC.Oral,intravenous,and rectal drug delivery nanoparticles targeting the colon are discussed,which can provide ideas for the design of colon-targeting nanoparticles for the treatment of colon diseases,especially for the treatment of UC.Last but not least,we provide a glimpse into the future of colon-targeted delivery systems,as well as future advancements in the field.

Pectin-chitosan complex: Preparation and application in colon-specific capsule

Pectin-chitosan complex was prepared as a candidate material for colon-specific capsule.First,the effects of beating on the properties of complex films were explored.Fourier transform infrared(FT-IR)spectroscopy was used to analyze the reaction mechanics,and an in vitro simulation experiment was performed to determine the degradation performance.Second,the capsule was prepared using pectin-chitosan complex as the main raw material;its targeting effect was evaluated and analyzed.Results indicated that the film became smooth and compact by beating.FT-IR data indicated that cross-linking occurred between the hydroxyl group of pectin and the amino group of chitosan to form a network structure.In vitro experiment showed that the pectin-chitosan complex film could not be degraded in the simulated gastric and intestinal fluids.However,pectin-chitosan complex could be degraded in the simulated colonic fluid,so it could be a potential candidate for colon-specific capsule.Because the complex has no ability for forming hard capsule,the carrageenan and starch were added to increase the flexibility,gelation,transparency and mechanical properties of the film.The preferred composition suitable for preparing the capsule was a mass ratio(2:1:1)of pectin-chitosan/carrageenan/starch mixture.The capsule showed excellent features in terms of shape,water content,and brittleness.The drug release rate reached 93.33%in colonic fluid for 1 h when bovine serum albumin was the model drug.Therefore,pectin-chitosan may be considered as a new material for colon-targeted capsule.

The influence of the gut microbiota on the bioavailability of oral drugs

Due to its safety,convenience,low cost and good compliance,oral administration attracts lots of attention.However,the efficacy of many oral drugs is limited to their unsatisfactory bioavailability in the gastrointestinal tract.One of the critical and most overlooked factors is the symbiotic gut microbiota that can modulate the bioavailability of oral drugs by participating in the biotransformation of oral drugs,influencing the drug transport process and altering some gastrointestinal properties.In this review,we summarized the existing research investigating the possible relationship between the gut microbiota and the bioavailability of oral drugs,which may provide great ideas and useful instructions for the design of novel drug delivery systems or the achievement of personalized medicine.

4-氨基水杨酸麦芽糖苷盲结肠定位给药系统的体外评价

目的:研究4-氨基水杨酸(4-ASA)麦芽糖苷(Mal)的体外盲结肠定位释药特征。方法:采用高效液相色谱法,以4-ASA的累积释放率为指标,分别考察4-ASA-Mal(相当于250μg/ml的4-ASA)在不同p H(1.2、6.8、7.4)缓冲液、正常大鼠和溃疡性结肠炎模型大鼠不同部位(胃、小肠、盲肠、结肠)内容物液中的释药行为。结果:4-ASA-Mal在不同p H缓冲液中几乎不释放;在正常和模型大鼠胃和小肠的内容物液中12 h的累积释放率均小于8%;在正常大鼠盲肠和结肠内容物液中12 h的累积释放率分别为55%和81%;在溃疡性结肠炎模型大鼠盲肠和结肠内容物液中12 h的累积释放率分别为55%和74%。结论:4-ASA-Mal可在体外盲结肠内容物液中定位大量释放4-ASA,具有盲结肠靶向性。