João Marcelo de Castro e Sousa

Starch-based coatings for colon-specific drug delivery. Part I: The influence of heat treatment on the physico-chemical properties of high amylose maize starches

In this study, the changes in the physico-chemical properties of different high amylose maize starches, i.e., Hylon VII, Hylon V and IM-DS acetate starch, were studied prior and after heat treatment used in the preparation of film coatings (WO 2008/012573 A1). Characterisation of the unprocessed maize starches was carried out with regard to the outer particle morphology, particle size distribution, specific surface area, moisture content, apparent particle density, swelling, polarised light microscopy, Fourier Transform Infrared (FT-IR), X-ray powder diffraction and modulated Differential Scanning Calorimetry (mDSC). Pure amylopectin and low amylopectin samples (LAPS) were also used to aid the interpretation of the results. The effect of heat processing was evaluated in terms of degree of crystallinity, FT-IR and mDSC. Enzymatic digestibility of both processed and unprocessed maize starches was estimated qualitatively using various alpha-amylases resembling those present under in vivo conditions. A significant decrease in the degree of crystallinity of the dried samples after processing was observed, in particular for amylopectin. Only LAPS and Hylon VII samples showed differences in their thermal behaviour upon heat treatment, thus suggesting that a minimum amount of amylose is required for an effect to be detectable. High amylose starches maintained a well-ordered arrangement of their macromolecular chains, as was seen by X-ray and FT-IR studies. This effect could be explained by a formation of retrograded forms of the starches. The retrograded starches were found to be less digestible by various types of amylase, in particular those found in the upper intestines, indicating that the formation of a butanol complex as claimed elsewhere is not essential in the preparation of colon delivery devices.

Passive and active strategies for transdermal delivery using co-encapsulating nanostructured lipid carriers: in vitro vs. in vivo studies.

This work aimed at designing a formulation based on nanostructured lipid carriers (NLC) for transdermal co-administration of olanzapine and simvastatin, using passive and active strategies in a combined in vitro/in vivo development approach. NLC were prepared by two distinct methods, namely solvent emulsification-evaporation (SE/E) and high pressure homogenization (HPH). HPH was selected on the basis of a better performance in terms of drug loading and in vitro permeation rate. Several mathematical models were used to elucidate the release mechanisms from lipid nanoparticles. In vitro release kinetics was shown to be driven by diffusion, but other mechanisms were also present, and supported the feasibility of using NLC for sustained drug delivery. The in vitro skin studies showed that the chemical penetration enhancers, limonene and ethanol, added to the NLC formulations, promoted a synergistic permeation enhancement of both drugs, with olanzapine exhibiting a higher permeation than simvastatin. Transdermal administration to rats resulted in steady-state levels reached at around 10h and maintained for 48h, again with olanzapine exhibiting a better permeation rate. The pharmacokinetic parameters indicated that the NLC dispersion displayed a better in vivo performance than the gel, which was consistent with the in vitro results. These differences were, however, negligible in the flux values, supporting the use of gel as a final, more convenient, formulation. The in vivo experiments in rats correlated well with in vitro findings and revealed that the combined use of ethanol and limonene, incorporated in the NLC formulation, provided the main driving force for drug permeation. The Dermaroller® pretreatment did not significantly enhance drug permeation, supporting the use of passive methods as suitable for a transdermal delivery system. Furthermore, this work may provide a promising proof-of-concept for further clinical application in the treatment of schizophrenia and associated disorders, combined with dyslipidemia.

Influence of the coating formulation on enzymatic digestibility and drug release from 5-aminosalicylic acid pellets coated with mixtures of high-amylose starch and Surelease ® intended for colon-specific drug delivery

Background: Colon-specific delivery of drugs can be achieved with dosage forms coated with biopolymers that are metabolized selectively by the colonic microflora and yet resistant to enzymatic digestion in the small intestine. Aim: The aim of this study was to study the influence of formulation factors on the performance of mixed films from high-amylose starches and Surelease®, applied using a spray-coating process, as potential colon-specific delivery devices. Methods: 5-Aminosalicylic acid-loaded pellets were prepared by an extrusion-spheronization process and film coated with mixtures of the starches and Surelease®. Optimization of the coating formulation, that is, starch-to-Surelease® ratio, film-coating thickness, and type of starch, was undertaken first in enzyme-free media resembling the conditions in the stomach and small intestine. The effect of curing of the film coating on the drug release profile upon storage was also evaluated. Optimized coating formulations were further assessed for enzymatic digestibility using artificial gastric and intestinal juices containing commercially available pepsin and pancreatin or α-amylase from hog pancreas, respectively. Finally, drug release was assessed in fluid-simulating conditions in the colon (SCF) containing Bacillus licheniformis α-amylase. Results: Film coatings comprising high-amylose starches and Surelease® in a ratio of 1:2 (w/w) and film thickness of approximately 45 μm were able to withstand the chemical and enzymatic environment of the upper gastrointestinal tract, in particular, resisted degradation by the pancreatic α-amylases. Stability of the coatings during storage was achieved with additional curing. In SCF, these coatings were susceptible to enzymatic degradation. Conclusions: This study showed that high amylose starch-mixed films can be successfully used as colon-specific delivery devices. The preparation of the coating dispersions described is simple and rapid, without the need to extract the amylose component of starch.

Blood-retinal barrier permeability and its relation to progression of retinopathy in patients with type 2 diabetes. A four-year follow-up study

Forty patients with late-onset diabetes (age at diagnosis 30 years or more) and minimal retinopathy as found by fundus photography were followed prospectively by repeated examination (baseline, 1 year, and 4 years). The study shows that early retinopathy changes are not permanent or invariably progressive. In the 1st year of follow-up microaneurysms worsened in 25%, improved in 10%, and remained stabilized in 65%. Vitreous fluorometry was able to detect an overall increase of 0.84 ± 1.06 × 10−6 min−1 in blood-retinal barrier (BRB) penetration ratios. After 4 years, 16 of the 40 patients had undergone photocoagulation (focal photocoagulation in 11 and pan retinal photocoagulation in 5). The eyes that needed photocoagulation were the eyes that had higher fluorometry penetration ratios at the patients entry into the study and showed a higher rate of deterioration during the 1st year of the study (5.54 ±1.97 vs 3.11± 1.22 × 10−1 min−1,P<0.001, initial values; 1.52 ± 0.76 vs 0.45 ± 0.99 × 10i−6 min−1,P< 0.001, annual increase in leakage). The eyes that did not need photocoagulation, 24 out of 40, showed stable fluorometry readings within the 4-year period of follow-up (+0.02 ± 0.98 10−6 min−1). Abnormally high vitreous fluorometry values and their rapid increase over time appear to be good indicators of rapid progression and worsening of the retinopathy.

Liberação específica de fármacos para administração no cólon por via oral. I -O cólon como local de liberação de fármacos

Drug delivery to the colon has become attractive to researchers interested in the treatment of local diseases and for its potential for the delivery of proteins and therapeutic peptides. The treatment of colonic disorders like the inflammatory bowel disease can be improved by the use of systems capable of delivering the appropriate pharmacological agent selectively in the active site of inflammation, because it reduces the oral dose and its systemic side effects. The activity of the peptidases in the colon is very low, which makes possible to such labile molecules like proteins and peptides to be orally administered, without compromising their bioavailability. In the development of these systems it is fundamental to fully understand the colon as a site for drug delivery and, in particular, aspects like transit time, pH and enzyme activity of the colon, which are the basic mechanisms used to trigger release of a drug in the colon. Another important aspect is the absorptive capacity of the colon. In this context, the long residence time and the presence of some biological and chemical barriers might, respectively, enhance or limit drug absorption. The impact of the active inflammatory bowel disease on the efficacy of the systems used for targeting drugs to the colon might have been underestimated, since this pathology can alter the colonic pH and the enzyme activity of the colon.

Estudos de mucoadesão no trato gastrointestinal para o aumento da biodisponibilidade oral de fármacos

The oral bioavailability of many drugs can be limited by the residence time of pharmaceutical dosage forms in the gastrointestinal tract. Mucoadhesion has been proposed as a method to increase residence time at a specific area, hence increasing the therapeutic effect of drugs. Most research efforts on mucoadhesion have focused on the stomach and small intestine, with promising results observed from in in vitro studies. However, γ-scintigraphy data obtained in human studies have revealed the lack of success of mucoadhesion approaches in order to increase the contact time of formulations in the upper gut. The lack of in vitro/in vivo correlation can be attributed to the complex nature of the human gastrointestinal tract, with most in vitro models providing little resemblance to the in vivo situation, such as motility, pH, mucus thickness and mucus turnover, presence of enzymes and food. In the colon, the mucus turnover, the sensibility to mucus secretory stimulus and motility are lower than in the stomach and small intestine. Therefore, colonic mucoadhesion may be a more successful approach. Nevertheless, more studies in animals and humans are needed to evaluate its potential, as well as, pharmacokinetic studies to investigate drug release and absorption from mucoadhesive systems.

In vivo Antigenotoxic and Anticlastogenic Effects of Fresh and Processed Cashew (Anacardium occidentale) Apple Juices

Cashew apple juice and cajuina (processed juice) are drinks widely consumed in northeast Brazil. In vitro studies have shown that both juices have antimutagenic activity as well as antioxidant effects. These juices contain vitamins, carotenoids, and phenolic compounds. This in vivo study assessed the antigenotoxic and anticlastogenic effects of both drinks against genotoxicity and mutagenicity induced by cyclophosphamide. The comet, micronucleus, and chromosome aberrations tests were used. Male Swiss mice were divided into 6 groups (5 animals per group) and received the following by gavage, 0.15 mL/10 g body weight: group 1, water; group 2, cashew apple juice; group 3, cajuina juice; group 4, cashew apple juice and cyclophosphamide (50 mg/kg); group 5, cajuina juice and cyclophosphamide; group 6: cyclophosphamide. Both drinks significantly reduced DNA damage of peripheral blood cells (P<.001), with modulation percentages of 60.82% (cashew apple juice) and 82.19% (cajuina) when compared with the cyclophosphamide group. Cashew apple juice and cajuina modulated cyclophosphamide-induced micronucleus frequency, with up to 80.0% inhibition. Cashew apple juice and cajuina decreased the average number of cells with chromosome aberrations in bone marrow of mice by 53% and 65%, respectively. These findings demonstrate the high antigenotoxic and anticlastogenic potential of cashew apple juice and cajuina in vivo, which can be related to the antioxidant compounds found in both drinks.

Assessment of the in-vivo drug release from pellets film-coated with a dispersion of high amylose starch and ethylcellulose for potential colon delivery

Objectives The aim of this study was to test the ability of a colon targeting system comprising pellets film‐coated with a dispersion of high amylose starch (Hylon VII) and ethylcellulose (Surelease) (1 : 2 w/w) to deliver a model drug (5‐aminosalicylic acid; 5‐ASA) in vivo into the colon of rabbits. An uncoated pellet formulation was used as a control.

Breaching barriers in glioblastoma. Part I: Molecular pathways and novel treatment approaches

Glioblastoma multiforme (GBM) is the most common primary brain tumour, and the most aggressive in nature. The prognosis for patients with GBM remains poor, with a median survival time of only 1-2 years. The treatment failure relies on the development of resistance by tumour cells and the difficulty of ensuring that drugs effectively cross the dual blood brain barrier/blood brain tumour barrier. The advanced molecular and genetic knowledge has allowed to identify the mechanisms responsible for temozolomide resistance, which represents the standard of care in GBM, along with surgical resection and radiotherapy. Such resistance has motivated the researchers to investigate new avenues for GBM treatment intended to improve patient survival. In this review, we provide an overview of major obstacles to effective treatment of GBM, encompassing biological barriers, cancer stem cells, DNA repair mechanisms, deregulated signalling pathways and autophagy. New insights and potential therapy approaches for GBM are also discussed, emphasizing localized chemotherapy delivered directly to the brain, immunotherapy, gene therapy and nanoparticle-mediated brain drug delivery.

Liberação específica de fármacos no cólon por via oral. II - Tipos de sistemas utilizados

Two basic approaches may be taken in delivering drugs to the colon: time-delayed release or colonic targeting. The former involves sustained release dosage forms, which are designed to prolong drug dissolution and hence absorption, until it reaches the colon. This strategy shows lack of specificity when compared with others that take advantage of unique characteristics present in the colon. Direct targeting involves the exploitation of environmental properties of the colon, like pH of the colon, enzymatic activity or intraluminal pressure. In general, the ideal colonic drug delivery may be accomplished by using pellets, which are known to have more predictable gastric emptying and great colonic residence times, and coated dosage forms with a simple design since they are easy to manufacture. Theoretically, the enzyme dependent systems, and, specially, those based in the use of polysaccharides, are more specific and non-toxic. Nevertheless, any of the others approaches might be suitable to obtain a colonic delivery system with the appropriate characteristics. Some commercially time-dependent and pH-dependent systems have shown important benefits in the treatment of inflammatory bowel disease, despite their less specificity. The investigations in this field should be conducted to identify the appropriate approach, which can result in the delivery of drugs in a safe, effective and less expensive manner with minimum fluctuation in terms of release of drug at target site.