pH triggered delivery of curcumin from Eudragit-coated chitosan microspheres for inflammatory bowel disease: characterization and pharmacodynamic evaluation

Objective: This investigation deals with the development and evaluation (in vitro and in vivo) of pH triggered Eudragit-coated chitosan microspheres of curcumin (CUR) for treating ulcerative colitis.

Methods: CUR-loaded chitosan microspheres were initially prepared by emulsion cross linking method followed by coating with Eudragit S-100. The pharmacodynamics of the developed formulation was analyzed in mice by acetic acid induced colitis model.

Results: The developed microspheres were of uniform spherical shape with high entrapment efficiency. CUR-chitosan microspheres showed less intense peaks compared to free CUR confirming inclusion of drug within microspheres as revealed by X-ray diffractogram. Uncoated CUR-chitosan microspheres exhibited burst release within initial 4?h while microspheres coated with Eudragit S-100 prevented premature release of CUR and showed controlled release up to 12?h following Higuchi model. In vivo organ biodistribution study showed negligible amount of CUR in stomach and small intestine confirming integrity of microsphere in upper gastrointestinal tract (GIT). In vivo study revealed significant reduction in severity and extent of colonic damage with CUR-loaded microspheres as compared to pure CUR which was further confirmed by histopathological study.

Conclusion: In vitro and in vivo studies proved the developed formulations as a promising system for pH-dependent delivery of drug to colon in ulcerative colitis.     

Do cyclodextrins bound to dextran microspheres act as sustained delivery systems of drugs?

The use of cyclodextrins (CDs) for controlled delivery of drugs is largely presented in the literature. However, the question of whether CDs themselves linked to a polymeric network are able to sustain the release of drugs still persists. Here, CD immobilization within dextran microspheres is reported, and CD-dextran complexes were packed in a glass column and then, the retention time of different drugs and drug model compounds was determined by liquid chromatography. The release profiles of drugs and of drug model compounds (indole, 3-nitrophenol, p-hydroxybenzoic acid, diclofenac), characterized by different values of the retention time (high, moderate or low), were investigated. The release rates were quite high even for drugs that exhibit very high retention time (high association equilibrium constant). Moreover, the volume of the release fluid strongly influences the rate of drug release. As a whole, “the sink conditions” must be continuously maintained, since at each drug concentration in the release medium, equilibrium occurs between the free and the CD-bound drug.     

青蒿琥酯通过介导铁死亡逆转结肠癌细胞5-氟尿嘧啶耐药的作用研究

目的 探讨青蒿琥酯(ART)通过介导铁死亡逆转结肠癌细胞对5-氟尿嘧啶(5-FU)耐药的作用。方法 以人结肠癌HT-29/5-FU耐药细胞株为研究对象,采用MTS法检测5-FU、ART以及5-FU+ART对HT-29/5-FU细胞的抑制作用,并计算其逆转耐药倍数;克隆形成实验检测HT-29/5-FU细胞克隆形成能力;流式细胞术检测细胞内活性氧(ROS)水平;试剂盒检测细胞内丙二醛(MDA)水平;Western blotting检测细胞内Nrf2和GPX4蛋白表达水平。结果 40μmol·L^-1ART可逆转HT-29/5-FU细胞对5-FU的耐药,逆转倍数为2.9倍;5-FU联合ART可抑制HT-29/5-FU细胞的克隆形成能力,升高细胞内ROS和MDA水平,并降低Nrf2及GPX4蛋白表达水平,且这些效应能够被铁死亡抑制剂Ferrostatin-1所逆转。结论 ART能够通过抑制Nrf2、GPX4表达诱导铁死亡,从而逆转HT-29/5-FU细胞对5-FU的耐药。     

口服结肠靶向释药系统的制备及应用

目的由于在治疗肠道或某些全身性疾病中具有特殊的优点,口服结肠靶向给药系统受到更多的关注。但消化道的复杂性导致影响药物在结肠靶向释药的因素较多,重现性不好。本文对经口服药物结肠靶向释药的生理因素、目前已有的制备技术及应用进行综述。     

Preparation and characterization of ethylcellulose microspheres containing 5-fluorouracil

Abstract

Ethylcellulose microspheres containing 5-fluorouracil (5-FU) were prepared by a solvent evaporation technique using light mineral oil as the continuous phase. The drug was suspended in the acetone solution of the polymer. Three drug/polymer ratios (1/1, 1/2 and 1/3) were utilized. The microspheres were studied with respect to size, drug content and surface characteristics; the higher the polymer content, the smoother the microspheres. The drug was suspended in the polymer and the drug loading was important (more than 90%) with the three types of microspheres. In vitro dissolution studies in phosphate buffer showed that the 5-FU release was dependent on the drug/polymer ratio for the 400–500 üm granulometric fraction.     

Mucoadhesive platforms for targeted delivery to the colon

A novel platform system, comprising a mucoadhesive core and a rapid release carrier, was designed for targeted drug delivery to the colon. Prednisolone pellets containing different carbomers, including Carbopol 971P, Carbopol 974P and Polycarbophil AA-1, with or without organic acids, were produced by extrusion-spheronization. Mucoadhesive pellets were coated with a new enteric double-coating system, which dissolves at pH 7. This system comprises an inner layer of partially neutralized Eudragit^® S and buffer salt and an outer coating of standard Eudragit^® S. A single layer of standard Eudragit S was also applied for comparison purposes. Dissolution of the coated pellets was assessed in USP II apparatus in 0.1 N HCl followed by Krebs bicarbonate buffer pH 7.4. Visualization of the coating dissolution process was performed by confocal laser scanning microscopy using fluorescent markers in both layers. The mucoadhesive properties of uncoated, single-coated and-double coated pellets were evaluated ex vivo on porcine colonic mucosa. Mucoadhesive pellets coated with a single layer of Eudragit^® S release its cargo after a lag time of 120 min in Krebs buffer. In contrast, drug release from the double-coated mucoadhesive pellets was significantly accelerated, starting at 75 min. In addition, the mucoadhesive properties of the core of the double coated pellets were higher than those from single-coated pellets after the core had been exposed to the buffer medium. This novel platform technology has the potential to target the colon and overcome the variability in transit and harmonize drug release and bioavailability.     

Exploiting microspheres as a therapeutic proficient doer for colon delivery: a review

Introduction: Colon-specific drug delivery systems have recently gained importance for delivering a variety of therapeutic agents via oral route. This mode offers the feasibility of treating colonic pathologies with less risk of bioburden to other organs/tissues and has been widely researched for the delivery of challenging drugs. Microspheres targeted to colon have occupied central position on drug delivery due to their small size that offers characteristic intrinsic properties attributable to the carrier.

Areas covered: The present deliberation precariously covers the capacious usage of microspheres for the treatment of local colonic pathologies like colon carcinomas, inflammatory bowel disease and parasitic diseases using natural as well as synthetic carriers. The write up also encompasses clinical application of microspheres.

Expert opinion: Microspheres have comprehensive potential to be marketed as the patient-friendly formulation, as it would provide direct treatment at the disease site and, consequently, lower dosing and reducing systemic side effects. Wherefore, the major obstacles in delivering drugs to the colon like the absorption and degradation pathways in the proximal part of GIT could be easily overcome, and also a range of pathologies from constipation and diarrhea to the exhaustive inflammatory bowel diseases and colon carcinoma could be cured.     

Modified dextran,heparin-based triggered release microspheres for cardiovascular delivery of therapeutic drugs using protamine as a stimulus

In this study, we describe the synthesis of an amine-modified acetalated dextran polymer, which is combined with heparin (HP) as the basis for a novel controlled release system. Dextran-amine (DEXAM) conjugates, synthesised using reductive amination, were incorporated into DEXAM/HP microspheres. HP binds to positively charged ammonium ions of the DEXAM conjugates, contributing to the structural integrity of the microspheres. Crystal violet (CV) was encapsulated inside DEXAM/HP microspheres as a model drug to test the system. Protamine with a high affinity for HP functioned as a trigger to release CV. DEXAM/HP microspheres were characterised by particle size, encapsulation efficiency, scanning electron microscope images, and in vitro release profile. Release of CV from microspheres varied with primary amine content of DEXAM conjugates, amount of HP, and concentration of protamine added. The system is considered for controlled delivery of agents without the necessity of chemical modification.     

Synthesis and characterization of cross-linked chitosan microspheres for drug delivery applications

The present study deals with the synthesis and characterization of cross-linked chitosan microspheres containing an hydrophilic drug, hydroquinone. The microspheres were prepared by the suspension cross-linking method using glutaraldehyde as the cross-linking agent of the polymer matrix. Perfectly spherical cross-linked hydrogel microspheres loaded with hydroquinone were obtained in the size range of 20–100 μm. The effect of the degree of polymer cross-linking, chitosan molecular weight, chitosan concentration and amount of the encapsulated drug on the hydroquinone release kinetics was extensively investigated. It was found that slower drug release rates were obtained from microspheres prepared by using a higher initial concentration of chitosan, a higher molecular weight of chitosan or/and a lower drug concentration. Most importantly, it was shown that the release rate of hydroquinone was mainly controlled by the polymer cross-linking density and, thus, by the degree of swelling of the hydrogel matrix.     

Development of enteric-coated calcium pectinate microspheres intended for colonic drug delivery

Enteric-coated calcium pectinate microspheres (MS) aimed for colon drug delivery have been developed, by using theophylline as a model drug. The influence of pectin type (amidated or non-amidated) and MS preparation conditions (CaCl2 concentration and cross-linking time) was investigated upon the drug entrapment efficiency and its release behaviour. Drug stability and drug-polymer interactions were studied by Differential Scanning Calorimetry, thermogravimetry, X-ray diffractometry and FTIR spectroscopy. Enteric coating with Eudragit S100 enabled maintenance of MS integrity until its expected arrival to colon. The coating was also useful to improve the stability of MS during storage, avoiding morphologic changes observed for uncoated MS stored under ambient conditions. Entrapment efficiency increased by reducing cross-linking time, and (only in the case of non-amidated pectin) by increasing CaCl2 concentration. On the other hand, release tests performed simulating the gastro-intestinal pH variation evidenced an inverse relationship between CaCl2 concentration and drug release rate, whereas no influence of both pectin type and cross-linking time was found. Unexpectedly, addition of pectinolytic enzymes to the colonic medium did not give rise to selective enzymatic degradation of MS. Notwithstanding this unforeseen result, coated MS prepared at 2.5% w/v CaCl2 concentration were able to adequately modulate drug release through a mixed approach of pH and transit time control, avoiding drug release in the gastric ambient, and reaching the colonic targeting where 100% release was achieved within less than 24h.     

Stomach-specific drug delivery of 5-Fluorouracil using ethylcellulose floating microspheres

A multiple-unit-type oral floating dosage form (FDF) of 5-Fluorouracil (5-FU) was developed to prolong gastric residence time for the treatment of stomach cancer. The floating microspheres were prepared by solvent evaporation method. The prepared microspheres were characterized for their micromeretic properties, floating behavior and entrapment efficiency; as well by Fourier transform infrared spectroscopy (FTIR), Differential scanning calorimetry (DSC), X-ray powder diffractometry (XRPD), thin layer chromatography (TLC) and scanning electron microscopy (SEM). The in vitro release studies and floating behavior were performed in HCl buffer pH 1.2, Phosphate buffer pH 4.5 and in Simulated Gastric Fluid (SGF). The best fit release kinetics was achieved with Higuchi plot. The yields of preparation were very high and low entrapment efficiencies were noticed with larger particle size for all the formulations. Mean particle size, entrapment efficiency and production yield were highly influenced by polymer concentration. It was concluded from the present investigation that porous Ethylcellulose microspheres are promising controlled release as well as stomach targeted carriers for 5-FU.     

Imprinted hydrophilic nanospheres as drug delivery systems for 5-fluorouracil sustained release

Molecularly imprinted hydrogel nanospheres as devices for the controlled/sustained release of 5-fluororacil in biological fluids were synthesized employing one-pot precipitation technique as the polymerization method. Methacrylic acid as a functional monomer and ethylene glycole dimethacrylate as a cross-linker were used in polymeric feed. Morphological and hydrophilic properties were determined by scanning electron microscopy and water content measurement, and recognition and selectivity properties of spherical molecularly imprinted polymers were compared with the spherical non-imprinted polymers, both in organic (acetonitrile) and water media. Finally, in vitro release studies were performed in plasma simulating fluids.     

Preparation and evaluation of alginate-chitosan microspheres for oral delivery of insulin

The alginate-chitosan microspheres with narrow size distribution were prepared by membrane emulsification technique in combination with ion (Ca²⁺) and polymer (chitosan) solidification. The preparation procedure was observed, and the physical properties (particle size distribution, surface morphology, chitosan distribution, zeta potential) of the microspheres were characterized. Subsequently, the microspheres were employed to load model peptide of insulin. The effect of loading ways on the loading efficiency and immunological activity of insulin were investigated. It was shown that the higher loading efficiency (56.7%) and remarkable activity maintenance (99.4%) were obtained when the insulin was loaded during the chitosan solidification process (Method B). Afterward, the release profile in vitro for the optimal insulin-loaded microspheres was investigated. Under the pH conditions of gastrointestinal environment, only 32% of insulin released during the simulated transit time of drug (2 h in the stomach and 4 h in the intestinal). While under the pH condition of blood environment, insulin release was stable and sustained for a long time (14 days). Furthermore, the chemical stability of insulin released from the microspheres was well preserved after they were treated with the simulated gastric fluid containing pepsin for 2 h. Finally, the blood glucose level of diabetic rats could be effectively reduced and stably kept for a long time (∼60 h) after oral administration of the insulin-loaded alginate-chitosan microspheres. Therefore, the alginate-chitosan microspheres were found to be promising vectors showing a good efficiency in oral administration of protein or peptide drugs.     

5-氮杂-2-脱氧胞苷提高结肠癌SW620细胞株对5-FU的化学敏感性

目的 探讨5-氮杂-2-脱氧胞苷(5-aza-CdR)可能增强结肠癌SW620细胞株对5-氟尿嘧啶(5-FU)化学敏感性的作用.方法 分别用不含药物组(A组)、5-aza-CdR(B组)、5-FU(C组)以及5-aza-CdR联合5-FU(D组)作用人结肠癌SW620细胞株后,光镜下观察细胞形态学改变,MTT法测定细胞的生长情况和流式细胞术检测细胞凋亡.结果 A、B、C、D组细胞存活率分别为100％、(65.85±0.95)％、(45.14±1.44)％、(30.18±0.89)％;B、C、D组细胞存活率均明显低于A组(P＜0.05),D组低于B、C组(P＜0.05).A、B、C、D组细胞凋亡率分别为(4.50±0.61)0％、(16.80±0.57)％、(12.66±0.43)％、(42.07±0.85)％;与A组比较,B、C、D组引起细胞凋亡增加(P＜0.05);与B组、C组比较,D组促进细胞凋亡作用更明显(P＜0.05).结论 5-aza-CdR在体外提高了结肠癌SW620细胞对5-FU的化学敏感性.     

Targeted delivery of diclofenac sodium via gelatin magnetic microspheres formulated for intra-arterial administration

In the present work, we have attempted to deliver diclofenac sodium to a target site by intra-arterial injection of gelatin magnetic microspheres and subsequent localization using an external magnet. Drug-loaded magnetic microspheres were prepared by emulsification/cross-linking method, characterized by drug loading, magnetite content, size distribution, optical microscopy, scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) analysis, differential scanning calorimetry (DSC), X-ray diffraction (XRD), absence of glutaraldehyde by gas chromatography, and in vitro release studies. The targeting efficiency and the therapeutic efficacy of microspheres were studied in vivo in rabbits. The microspheres showed drug loading of 9.1, 18.7, 24.9% w/w, magnetite content of 27.8–28.9% w/w with an average size range of 25–30.6 μm, depending upon the drug–polymer ratio. They were spherical in nature as evidenced by optical microscopy and SEM. FT-IR, DSC, and XRD studies revealed the absence of drug–polymer interaction. Gas chromatography confirmed the absence of residual glutaraldehyde. The microspheres were able to prolong the drug release over 24–30 days and the application of sonication during in vitro release study has slightly increased the release rate. After intra-arterial administration of microspheres, 77.7% of injected dose was recovered at the target site which revealed good targeting efficiency. The microspheres effectively reduced joint swelling, but lesser extent than the oral diclofenac sodium in high dose, in antigen induced arthritic rabbits without producing gastric ulceration which was observed in rabbits treated with oral diclofenac sodium.     

Effects of alginate coated on PLGA microspheres for delivery tetracycline hydrochloride to periodontal pockets

The effects of alginate coated on tetracycline (Tc) loaded poly (D, L-lactic-co-glycolic acid) (PLGA) microspheres fabricated by double emulsion solvent evaporation technique for local delivery to periodontal pocket were investigated. Alginate coated PLGA microspheres showed smoother surface but enlarged their particle sizes compared with those of uncoated ones. In addition, alginate coated microspheres enhanced Tc encapsulation efficiency (E.E.) from 11.5?±?0.5% of uncoated ones to 17.9?±?0.5%. Moreover, all of the coated PLGA microspheres even fabricated at different conditions could prolong Tc release from 9–12 days with 50% or higher in cumulative release of Tc compared with those of uncoated ones. The swelling ratios of PLGA microspheres for alginate coated or uncoated ones, one of the possible mechanisms for enhancing Tc release for the coated ones, were measured. The results showed that 20% or higher in swelling ratio for the coated microspheres at the earlier stage of hydration (e.g.?≤?24?h) could be an important factor to result in high Tc release compared to the uncoated ones. In conclusion, alginate coated Tc loaded PLGA microspheres could enhance Tc delivery to periodontal pocket by enhancing drug encapsulated efficiency, released quantities and sustained release period compared with uncoated ones.     

Development of novel combined time and pH-dependent based drug delivery systems for targeting 5-fluorouracil to the colon

The present work is aimed to develop new oral drug delivery systems of 5-fluorouracil for the treatment of colorectal cancer by using hydrophilic swellable polymer hydroxy propyl methyl cellulose (HPMC) and pH responsive soluble polymer Eudragit L100 (ED) as coating materials. Core tablets containing 50mg of 5-fluorouracil were prepared by direct compression. The core tablets compression coated with different ratios (9:1, 8:2, 7:3, 6:4 and 5:5) of HPMC and ED with a coat weight of 300 and 400mg. All the formulations were evaluated for the hardness, friability, drug content uniformity and in vitro drug release studies in media of different pH 1.2, 7.4 and 6.8. The formulations released 0 to 7% of the drug in physiological environment of stomach and small intestine depending upon proportion of HPMC and ED used in the coat. Among the different ratios used for coating with HPMC:ED combination, ratio 9:1 gave the best release profile with the coat weight of 300mg (1.34% in the initial 5h and 87% in 24 h). Further increase in the coat weight to 400mg with different ratios of 9:1, 8:2, 7:3, 6:4 and 5:5 led to drug release of 0%, 0%, 0%, 3.47% and 6.25%, respectively in the initial 5 h and 73.52%, 87.03%, 92.18%, 96.33% and 97.61%, respectively, in 24 h. Thus, based on the results of in vitro drug release studies, the ratio 7:3 with a coat weight of 400mg was found to be suitable for targeting 5-fluorouracil to the colon without being released in physiological environment of stomach and small intestine. The formulation showed no change in physical appearance, drug content or in vitro release pattern after storage at 40° C / 75% RH for 3 months. The release of 5-fluorouracil from developed formulation was directly proportional to amount of ED used in the coat. The DSC and FTIR studies indicated no possibility of interaction between 5-fluorouracil and excipients.     

Fast-responsive porous thermoresponsive microspheres for controlled delivery of macromolecules

Porous thermoresponsive microspheres with a homogeneous dimension and distribution of the pores are synthesized by an original method. Poly(N-isopropylacrylamide-co-acrylamide) (poly(NIPAAm-co-AAm)) copolymer was obtained as a thermoresponsive material with a lower critical solution temperature (LCST) under physiologic-like conditions (i.e., at 37 °C and pH 7.4, 50 mM phosphate buffer). Semitelechelic oligomers of NIPAAm (ONIPAAm) were also synthesized in the presence of 3-mercaptopropionic acid (MPA) (chain transfer molecule) which acts as a pore-forming agent. Poly(NIPAAm-co-AAm) and ONIPAAm were solubilized in acidified aqueous solution, dispersed in a mineral oil, and transformed in stable microspheres by crosslinking the amide group with glutaraldehyde at temperatures below and above the LCST of the oligomers, and always below the LCST of the polymer. Microspheres obtained at temperatures below the LCST of ONIPAAm are characterized by a homogeneous porous structure with a narrow distribution of the pore size. These microspheres are characterized by a very rapid response rate when the temperature changes below and above the body temperature. The higher is the amount of the porogen in the polymer solution, the larger is the pore size and faster is the response rate. The porous microspheres with suitable pore size are a conveyable matrix for loading and temperature-controlled release of the high molecular weight model drug blue dextran (BD).     

雷公藤内酯醇联合5-氟尿嘧啶对结肠癌的作用研究

目的研究雷公藤内酯醇（TPL）与5-氟尿嘧啶（5-Fu）联合应用对结肠癌细胞增殖、凋亡及瘤体生长的影响并观察其在结肠癌化疗中的毒副作用。方法常规培养HT-29细胞，应用四甲基偶氮唑蓝比色法、流式细胞术检测TPL、5-FU联合应用对人结肠癌细胞增殖和凋亡的影响；中效原理评价两药的联合作用；建立裸鼠荷人结肠癌动物模型，分别及联合应用0．25mg／（kg·d）TPL和12mg／（kg·d）5-FU对其进行治疗，观察荷瘤裸鼠一般情况、瘤体的生长及化疗毒副作用。结果（1）TPL和5-FU分别及联合应用，在一定浓度范围内对结肠癌细胞有明显的增殖抑制和诱导凋亡作用，并且联合用药作用明显强于单独用药，48h凋亡率高达（41．71±1．38）％；（2）TPL和5-Fu单独应用均可抑制结肠癌瘤体的生长，肿瘤抑制率分别为78．53％、84．16％；2者联合应用时作用更为明显，肿瘤抑制率达96．78％；（3）整个化疗过程中除偶尔出现全身散在红斑、丘疹外，未见明显造血系统、肝肾功能损害等毒副作用。结论TPL与5-Fu联合应用比单独应用对结肠癌细胞株增殖抑制作用更强；TPL与5-FU在小剂量联合应用时协同抑制肿瘤细胞增殖，抑制瘤体生长，并能促进结肠癌细胞凋亡，在体外实验中毒副作用小。