Mucoadhesives in the gastrointestinal tract: revisiting the literature for novel applications

A review on revolutionizing ophthalmic therapy: Unveiling the potential of chitosan, hyaluronic acid, cellulose, cyclodextrin, and poloxamer in eye disease treatments

Ocular disorders, encompassing both common ailments like dry eye syndrome and more severe situations for instance age-related macular degeneration, present significant challenges to effective treatment due to the intricate architecture and physiological barriers of the eye. Polysaccharides are emerging as potential solutions for drug delivery to the eyes due to their compatibility with living organisms, natural biodegradability, and adhesive properties. In this review, we explore not only the recent advancements in polysaccharide-based technologies and their transformative potential in treating ocular illnesses, offering renewed optimism for both patients and professionals but also anatomy of the eye and the significant obstacles hindering drug transportation, followed by an investigation into various drug administration methods and their ability to overcome ocular-specific challenges. Our focus lies on biological adhesive polymers, including chitosan, hyaluronic acid, cellulose, cyclodextrin, and poloxamer, known for their adhesive characteristics enhancing drug retention on ocular surfaces and increasing bioavailability. A detailed analysis of material designs used in ophthalmic formulations, such as gels, lenses, eye drops, nanofibers, microneedles, microspheres, and nanoparticles, their advantages and limitations, the potential of formulations in improving therapeutic outcomes for various eye conditions. Moreover, we underscore the discovery of novel polysaccharides and their potential uses in ocular drug delivery.

The Potential of Films as Transmucosal Drug Delivery Systems

Pharmaceutical films are polymeric formulations used as a delivery platform for administration of small and macromolecular drugs for local or systemic action. They can be produced by using synthetic, semi-synthetic, or natural polymers through solvent casting, electrospinning, hot-melt extrusion, and 3D printing methods, and depending on the components and the manufacturing methods used, the films allow the modulation of drug release. Moreover, they have advantages that have drawn interest in the development and evaluation of film application on the buccal, nasal, vaginal, and ocular mucosa. This review aims to provide an overview of and critically discuss the use of films as transmucosal drug delivery systems. For this, aspects such as the composition of these formulations, the theories of mucoadhesion, and the methods of production were deeply considered, and an analysis of the main transmucosal pathways for which there are examples of developed films was conducted. All of this allowed us to point out the most relevant characteristics and opportunities that deserve to be taken into account in the use of films as transmucosal drug delivery systems.

Bio-Inspired Muco-Adhesive Polymers for Drug Delivery Applications

Muco-adhesive drug delivery systems continue to be one of the most studied for controlled pharmacokinetics and pharmacodynamics. Briefly, muco-adhesive polymers, can be described as bio-polymers that adhere to the mucosal (mucus) surface layer, for an extended residency period of time at the site of application, by the help of interfacial forces resulting in improved drug delivery. When compared to traditional drug delivery systems, muco-adhesive carriers have the potential to enhance therapeutic performance and efficacy, locally and systematically, in oral, rectal, vaginal, amongst other routes. Yet, the achieving successful muco-adhesion in a novel polymeric drug delivery solution is a complex process involving key physico-chemico-mechanical parameters such as adsorption, wettability, polymer chain length, inter-penetration and cross-linking, to list a few. Hence, and in light of accruing progress, evidence and interest, during the last decade, this review aims to provide the reader with an overview of the theories, principles, properties, and underlying mechanisms of muco-adhesive polymers for pharmaceutics; from basics to design to characterization to optimization to evaluation to market. A special focus is devoted to recent advances incorporating bio-inspired polymers for designing controlled muco-adhesive drug delivery systems.

Triborheological Analysis of Reconstituted Gastrointestinal Mucus/Chitosan:TPP Nanoparticles System to Study Mucoadhesion Phenomenon under Different pH Conditions

Polymeric nanoparticles have attracted much attention as pharmaceutical delivery vehicles to prolong residence time and enhance the bioavailability of therapeutic molecules through the mucoadhesive phenomenon. In this study, chitosan:TPP nanoparticles were synthetized using the ionic gelation technique to analyze their mucoadhesive interaction with reconstituted porcine gastrointestinal mucus from a triborheological point of view under different pH conditions (pH = 2.0, 4.0, 6.0 and 7.0). The triborheological profile of the reconstituted mucus was evaluated at different pH environments through the oscillation frequency and the flow sweep tests, demonstrating that the reconstituted mucus exhibits shear thinning behavior regardless of pH, while its viscoelastic properties showed a change in behavior from a polymeric solution performance under neutral pH conditions to a viscoelastic gel under acidic conditions. Additionally, a rheological synergism analysis was performed to visualize the changes that occur in the viscoelastic properties, the viscosity and the coefficient of friction of the reconstituted mucus samples as a consequence of the interaction with the chitosan:TPP nanoparticles to determine or to discard the presence of the mucoadhesion phenomenon under the different pH values. Mucoadhesiveness evaluation revealed that chitosan:TPP exhibited strong mucoadhesion under highly acidic pH conditions, below its pKa value of 6.5. In contrast, at neutral conditions or close to its pKa value, the chitosan:TPP nanoparticles' mucoadhesiveness was negligible.

Gastroretentive Technologies in Tandem with Controlled-Release Strategies: A Potent Answer to Oral Drug Bioavailability and Patient Compliance Implications

There have been many efforts to improve oral drug bioavailability and therapeutic efficacy and patient compliance. A variety of controlled-release oral delivery systems have been developed to meet these needs. Gastroretentive drug delivery technologies have the potential to achieve retention of the dosage form in the upper gastrointestinal tract (GIT) that can be sufficient to ensure complete solubilisation of the drugs in the stomach fluids, followed by subsequent absorption in the stomach or proximal small intestine. This can be beneficial for drugs that have an “absorption window” or are absorbed to a different extent in various segments of the GIT. Therefore, gastroretentive technologies in tandem with controlled-release strategies could enhance both the therapeutic efficacy of many drugs and improve patient compliance through a reduction in dosing frequency. The paper reviews different gastroretentive drug delivery technologies and controlled-release strategies that can be combined and summarises examples of formulations currently in clinical development and commercially available gastroretentive controlled-release products. The different parameters that need to be considered and monitored during formulation development for these pharmaceutical applications are highlighted.

Mucoadhesive Formulation Designs for Oral Controlled Drug Release at the Colon

Mucoadhesive formulations have been demonstrated to result in efficient drug delivery systems with advantages over existing systems such as increased local retention and sustained drug release via adhesiveness to mucosal tissues. The controlled release of colon-targeted, orally administered drugs has recently attracted a number of studies investigating mucoadhesive systems. Consequently, substantial designs, from mucoadhesive cores to shells of particles, have been studied with promising applications. This review will provide an overview of specific strategies for developing mucoadhesive systems for colon-targeted oral delivery with controlled drug release, including mucoadhesive matrices, cross-linked mucoadhesive microparticles, coatings and mucoadhesive nanoparticles. The understanding of the basic principle of these designs and advanced formulations throughout will lead to the development of products with efficient drug delivery at the colon for therapies for different diseases.

Tissue Adhesives: From Research to Clinical Translation

Sutures, staples, clips and skin closure strips are used as the gold standard to close wounds after an injury. In spite of being the present standard of care, the utilization of these conventional methods is precarious amid complicated and sensitive surgeries such as vascular anastomosis, ocular surgeries, nerve repair, or due to the high-risk components included. Tissue adhesives function as an interface to connect the surfaces of wound edges and prevent them from separation. They are fluid or semi-fluid mixtures that can be easily used to seal any wound of any morphology - uniform or irregular. As such, they provide alternatives to new and novel platforms for wound closure methods. In this review, we offer a background on the improvement of distinctive tissue adhesives focusing on the chemistry of some of these products that have been a commercial success from the clinical application perspective. This review is aimed to provide a guide toward innovation of tissue bioadhesive materials and their associated biomedical applications.

Why Chain Length of Hyaluronan in Eye Drops Matters

The chain length of hyaluronan (HA) determines its physical as well as its physiological properties. Results of clinical research on HA eye drops are not comparable without this parameter. In this article methods for the assessment of the average molecular weight of HA in eye drops and a terminology for molecular weight ranges are proposed. The classification of HA eye drops according to their zero shear viscosity and viscosity at 1000 s-1 shear rate is presented. Based on the gradient of mucin MUC5AC concentration within the mucoaqueous layer of the tear film a hypothesis on the consequences of this gradient on the rheological properties of the tear film is provided. The mucoadhesive properties of HA and their dependence on chain length are explained. The ability of HA to bind to receptors on the ocular epithelial cells, and in particular the potential consequences of the interaction between HA and the receptor HARE, responsible for HA endocytosis by corneal epithelial cells is discussed. The physiological function of HA in the framework of ocular surface homeostasis and wound healing are outlined, and the influence of the chain length of HA on the clinical performance of HA eye drops is illustrated. The use of very high molecular weight HA (hylan A) eye drops as drug vehicle for the next generation of ophthalmic drugs with minimized side effects is proposed and its advantages elucidated. Consequences of the diagnosis and treatment of ocular surface disease are discussed.

Synthesis and in vitro characterization of a preactivated thiolated acrylic acid/acrylamide-methylpropane sulfonic acid copolymer as a mucoadhesive sprayable polymer

AIM

Development of a preactivated thiomer as sprayable excipient for mucoadhesive formulations.

METHODS

CG4500 (acrylic acid/acrylamide-methyl propane sulfonic acid copolymer) was thiolated by conjugation with L-cysteine and preactivated by further modification with 2-mercaptonicotinic acid (MNA) in a two-step synthesis and characterized regarding degree of modification and cytotoxicity on Caco-2 cells. The mucoadhesive properties of this novel thiomer were evaluated via rheological synergism, tensile and mucosal residence time studies. Furthermore, the sprayability of the thiomer was evaluated.

RESULTS

The newly synthesized derivatives CG4500-SH and CG4500-S-S-MNA showed mean coupling rates of 651 µmol thiol groups and 264 µmol MNA per gram polymer, respectively. Even for the unmodified polymer a rheological synergism was observed with isolated porcine intestinal mucus, which was 2.81-fold higher in case of the preactivated thiomer. Mucoadhesion studies on freshly excised porcine intestinal mucosa confirmed these results via a 2.43-fold higher total work of adhesion and a 2.31-fold higher mucosal residence time of the preactivated thiomer. In sprayability tests it was shown that solutions of the preactivated thiomer could be sprayed in concentrations up to 12% (m/V).

CONCLUSION

The novel polymer CG4500-S-S-MNA is a promising sprayable excipient for mucoadhesive formulations.

Macro-Scale Tread Patterns for Traction in the Intestine

GOAL

Tread patterns are widely used to increase traction on different substrates, with the tread scale, geometry and material being tailored to the application. This work explores the efficacy of using macro-scale tread patterns for a medical application involving a colon substrate - renowned for its low friction characteristics.

METHODS

Current literature was first summarized before an experimental approach was used, based on a custom test rig with ex vivo porcine colon, to assess different macro-scale tread patterns. Performance was based on increasing traction while avoiding significant trauma. Repeated testing (n = 16) was used to obtain robust results.

RESULTS

A macro-scale tread pattern can increase the traction coefficient significantly, with a static traction coefficient of 0.74 ± 0.22 and a dynamic traction coefficient of 0.35 ± 0.04 compared to a smooth (on the macro-scale) Control (0.132 ± 0.055 and 0.054 ± 0.015, respectively). Decreasing the scale and spacing between the tread features reduced apparent trauma but also reduced the traction coefficient.

CONCLUSION

Significant traction can be achieved on colon tissue using a macro-scale tread but a compromise between traction (large feature sizes) and trauma (small feature sizes) may have to be made.

SIGNIFICANCE

This work provides greater insight into the complex frictional mechanisms of the intestine and gives suggestions for developing functional tread surfaces for a wide range of clinical applications.

Polysaccharides in Ocular Drug Delivery

Polysaccharides, such as cellulose, hyaluronic acid, alginic acid, and chitosan, as well as polysaccharide derivatives, have been successfully used to augment drug delivery in the treatment of ocular pathologies. The properties of polysaccharides can be extensively modified to optimize ocular drug formulations and to obtain biocompatible and biodegradable drugs with improved bioavailability and tailored pharmacological effects. This review discusses the available polysaccharide choices for overcoming the difficulties associated with ocular drug delivery, and it explores the reasons for the dependence between the physicochemical properties of polysaccharide-based drug carriers and their efficiency in different formulations and applications. Polysaccharides will continue to be of great interest to researchers endeavoring to develop ophthalmic drugs with improved effectiveness and safety.

Mucosal Applications of Poloxamer 407-Based Hydrogels: An Overview

Poloxamer 407, also known by the trademark Pluronic^® F127, is a water-soluble, non-ionic triblock copolymer that is made up of a hydrophobic residue of polyoxypropylene (POP) between the two hydrophilic units of polyoxyethylene (POE). Poloxamer 407-based hydrogels exhibit an interesting reversible thermal characteristic. That is, they are liquid at room temperature, but they assume a gel form when administered at body temperature, which makes them attractive candidates as pharmaceutical drug carriers. These systems have been widely investigated in the development of mucoadhesive formulations because they do not irritate the mucosal membranes. Based on these mucoadhesive properties, a simple administration into a specific compartment should maintain the required drug concentration in situ for a prolonged period of time, decreasing the necessary dosages and side effects. Their main limitations are their modest mechanical strength and, notwithstanding their bioadhesive properties, their tendency to succumb to rapid elimination in physiological media. Various technological approaches have been investigated in the attempt to modulate these properties. This review focuses on the application of poloxamer 407-based hydrogels for mucosal drug delivery with particular attention being paid to the latest published works.

Recent insights in the use of nanocarriers for the oral delivery of bioactive proteins and peptides

Bioactive proteins and peptides have been used with either prophylactic or therapeutic purposes, presenting inherent advantages as high specificity and biocompatibility. Nanocarriers play an important role in the stabilization of proteins and peptides, offering enhanced buccal permeation and protection while crossing the gastrointestinal tract. Moreover, preparation of nanoparticles as oral delivery systems for proteins/peptides may include tailored formulation along with functionalization aiming bioavailability enhancement of carried proteins or peptides. Oral delivery systems, namely buccal delivery systems, represent an interesting alternative route to parenteric delivery systems to carry proteins and peptides, resulting in higher comfort of administration and, therefore, compliance to treatment. This paper outlines an extensive overview of the existing publications on proteins/peptides oral nanocarriers delivery systems, with special focus on buccal route. Manufacturing aspects of most commonly used nanoparticles for oral delivery (e.g. polymeric nanoparticles using synthetic or natural polymers and lipid nanoparticles) advantages and limitations and potential applications of nanoparticles as proteins/peptides delivery systems will also be thoroughly addressed.

Mucoadhesive properties of low molecular weight chitosan- or glycol chitosan- and corresponding thiomer-coated poly(isobutylcyanoacrylate) core-shell nanoparticles

The aim of the present work was to evaluate the mucoadhesive properties of poly(isobutyl cyanoacrylate) (PIBCA) nanoparticles (NPs) coated with Low Molecular Weight (LMW) chitosan (CS)- and glycol chitosan (GCS)-based thiomers as well as with the corresponding LMW unmodified polysaccharides. For this purpose, all the CS- and GCS-based thiomers were prepared under simple and mild conditions starting from the LMW unmodified polymers CS and GCS. The resulting NPs were of spherical shape with diameters ranging from 400 to 600nm and 187 to 309nm, for CS- and GCS-based NPs, respectively. The mucoadhesive characteristics of these core shell NPs were studied in Ussing chambers measuring the percentage of NPs stuck on the mucosal of fresh intestinal tissue after 2h of incubation. Moreover, incubation of nanoparticle formulations with the intestinal tissue induced changes in transmucosal electrical resistance which were measured to gain information into the opening of tight junctions and to control the integrity of the mucosa. Thus, it was found that PIBCA NPs coated with the GCS-Glutathione conjugate (GCGPIBCA NPs) possessed the most favorable mucoadhesive performances. Moreover, both GCGPIBCA- and GCS-N-acetyl-cysteine (GCNPIBCA)-core-shell NPs might induced an enlargement of the epithelial cell tight junctions. In conclusion, coating of PIBCA NPs with GCS-based thiomers may be useful for improving the mucoadhesive and permeation properties of these nanocarriers.

Mucoadhesive microparticulates based on polysaccharide for target dual drug delivery of 5-aminosalicylic acid and curcumin to inflamed colon

In this work, thiolated chitosan/alginate composite microparticulates (CMPs) coated by Eudragit S-100 were developed for colon-specific delivery of 5-aminosalicylic acid (5-ASA) and curcumin (CUR), and the use of it as a multi drug delivery system for the treatment of colitis. The physicochemical properties of the CMPs were evaluated. In vitro release was performed in gradually pH-changing medium simulating the conditions of different parts of GIT, and the results showed that the Eudragit S-100 coating has a pH-sensitive release property, which can avoid drug being released at a pH lower than 7. An everted sac method was used to evaluate the mucoadhesion of CMPs. Ex vivo mucoadhesive tests showed CMPs have excellent mucosa adhesion for the colonic mucosa of rats. In vivo treatment effect of enteric microparticulates systems was evaluated in colitis rats. The results showed superior therapeutic efficiency of this drug delivery system for the colitis rats induced by TNBS. Therefore, the enteric microparticulates systems combined the properties of pH dependent delivery, mucoadhesive, and control release, and could be an available tool for the treatment of human inflammatory bowel disease.

Mucoadhesive therapeutic compositions: a patent review (2011-2014)

INTRODUCTION

With the introduction of mucoadhesion in 1980, pharmaceutical researchers have gained interest in mucoadhesive compositions. This interest has led to the development of mucoadhesive drug delivery systems aiming (I) to target a specific tissue, (II) to overcome barriers to absorption as well as (III) to control drug release of the therapeutic compositions.

AREAS COVERED

In this review, the term mucoadhesion and a variety of targetable mucosa are described through review of the literature. Mucoadhesive drug delivery systems and mucoadhesive polymers, such as thiomers, which are reported within the patent literature or in related publications are described in detail, including their therapeutic uses.

EXPERT OPINION

Mucoadhesion is associated with benefits such as controlled, sustained release, prolonged residence time at the site of action, the ability to target specific mucosae and ease of application which leads to higher rates of patient compliance. Although many research groups are investigating in this domain, not many drug delivery systems based on mucoadhesive polymers have got from bench to market. The most promising and advanced applications seen in patent literature within the last five years seems to be for oral application.

A mucoadhesive endoluminal wearable sensory system

Bio- or muco-adhesive anchoring is a challenge for the development of advanced gastrointestinal (GI) surgical instruments, endoluminal monitoring devices and drug delivery systems. In this paper, we present a polymeric bio-adhesive film embedded with an optical sensor that can potentially be used to detect gastrointestinal bleeding. Four different formulas of mucoadhesive polymers were synthesized based on various chemical components and concentration combinations, and they were further layered with miniature photoplethymographic (PPG) sensors. The adhesive ability of the proposed mucoadhesive-sensor module was tested by attaching it to the lumen of a porcine stomach and compared amongst the four formulas. pH testing was also implemented to simulate the performance of the film in gastric cavity. To demonstrate the signal quality of this module, we also tested on the skin of five healthy subjects for hours. The observed shear detachment force between mucoadhesive film and porcine stomach tissue of all four formulations ranged from 0.09 to 1.38 N, and the performance of mucoadhesive film in pH 7 and pH 2 were similar. The module can attach firmly onto the skin for 3-10 hours with comparable PPG signal quality to traditional clip-based setup. With the advent of mucosal tissue anchoring by means of bioadhensive film, a wider extent of endoluminal procedures may become feasible. This emerging technology can also help shape the future of in-body wearable devices in the GI tract or other endoluminal cavities.

Evaluation of nystatin containing chitosan hydrogels as potential dual action bio-active restorative materials: in vitro approach

Healing is a specific biological process related to the general phenomenon of growth and tissue regeneration and is a process generally affected by several systemic conditions or as detrimental side-effects of chemotherapy- and radiotherapy-induced inflammation of the oral mucosa. The objectives of this study is to evaluate the novel chitosan based functional drug delivery systems, which can be successfully incorporated into "dual action bioactive restorative materials", capable of inducing in vitro improved wound healing prototype and containing an antibiotic, such as nystatin, krill oil as an antioxidant and hydroxyapatite as a molecular bone scaffold, which is naturally present in bone and is reported to be successfully used in promoting bone integration when implanted as well as promoting healing. The hydrogels were prepared using a protocol as previously reported by us. The physico-chemical features, including surface morphology (SEM), release behaviors, stability of the therapeutic agent-antioxidant-chitosan, were measured and compared to the earlier reported chitosan-antioxidant containing hydrogels. Structural investigations of the reactive surface of the hydrogel are reported. Release of nystatin was investigated for all newly prepared hydrogels. Bio-adhesive studies were performed in order to assess the suitability of these designer materials. Free radical defense capacity of the biomaterials was evaluated using established in vitro model. The bio-adhesive capacity of the materials in the in vitro system was tested and quantified. It was found that the favorable synergistic effect of free radical built-in defense mechanism of the new functional materials increased sustainable bio-adhesion and therefore acted as a functional multi-dimensional restorative material with potential application in wound healing in vitro.

The complete functional recovery of chitosan-treated biomimetic hyperplastic and normoplastic urothelial models

The urinary tract is exposed to a variety of possible injures that may lead to organ damage or loss, and thus, the establishment of valid in vitro urothelial models to study the mechanism of drug candidates is necessary. This study is the first to investigate the effect of chitosan on urothelia in vitro and to evaluate whether chitosan-treated urothelial models can regenerate in vitro and reestablish a functional urothelium. Biomimetic hyperplastic and normoplastic urothelial models were used to test the effect of chitosan (0.05%) on partially and highly differentiated urothelial cells (UCs) by monitoring their molecular, ultrastructural, and physiological changes for 3 weeks. Chitosan caused an immediate and complete loss of transepithelial resistance (TER), tight junction disruption, cytopathological changes of UCs, and consequently enhanced the permeability of partially and highly differentiated urothelial models. However, 3 weeks after chitosan treatment, TER was reestablished, tight junctions resealed, permeability decreased, and progressive differentiation stages of newly exposed superficial UCs expressing uroplakins and tight junction protein claudin-8 were found. The in vitro models regenerated and reestablished urothelia with a tight barrier. The biomimetic urothelial models represent appropriate in vitro models for studying urothelial drug candidates as well as evaluating drug permeabilities and their intracellular function. Understanding the possible intracellular function of chitosan could significantly advance approaches to treating urothelial-specific diseases.

Whey protein and alginate hydrogel microparticles for insulin intestinal absorption: evaluation of permeability enhancement properties on Caco-2 cells

The evaluation of encapsulated insulin intestinal absorption enhancement was investigated by in vitro methods. Insulin-loaded microparticles (INS-MP) made of whey protein (WP) and alginate (ALG) were prepared by a cold gelation technique. Effect of INS encapsulation toward trypsin and chymotrypsin degradation was performed. Permeability studies using in vitro (Caco-2 cells) experiments were conducted. INS was partially protected by encapsulation toward enzymatic degradation. Moreover INS transport experiments showed that WP and, in lesser extent, ALG were able to enhance INS absorption both as MP and as polymeric solutions by opening the tight junctions. These experiments reinforced the interest of encapsulation in WP/ALG hydrogel combination.

Oral drug delivery systems using chemical conjugates or physical complexes

Oral delivery of therapeutics is extremely challenging. The digestive system is designed in a way that naturally allows the degradation of proteins or peptides into small molecules prior to absorption. For systemic absorption, the intact drug molecules must traverse the impending harsh gastrointestinal environment. Technologies, such as enteric coating, with oral dosage formulation strategies have successfully provided the protection of non-peptide based therapeutics against the harsh, acidic condition of the stomach. However, these technologies showed limited success on the protection of therapeutic proteins and peptides. Importantly, inherent permeability coefficient of the therapeutics is still a major problem that has remained unresolved for decades. Addressing this issue in the context, we summarize the strategies that are developed in enhancing the intestinal permeability of a drug molecule either by modifying the intestinal epithelium or by modifying the drug itself. These modifications have been pursued by using a group of molecules that can be conjugated to the drug molecule to alter the cell permeability of the drug or mixed with the drug molecule to alter the epithelial barrier function, in order to achieve the effective drug permeation. This article will address the current trends and future perspectives of the oral delivery strategies.

Toward mucoadhesive hydrogel formulations for the management of xerostomia: the physicochemical, biological, and pharmacological considerations

Although hydrogel formulations that may be applied to many mucosal surfaces are now readily accessible, little research effort has been concentrated on the development of systems that may be usefully employed for the prolonged hydration of the oral cavity. To this end, and set within the context of oral care in general, this review considers the requirements for the design of hydrogel formulations with an affinity for buccal cells and details methods for evaluating the performance of these formulations as treatments for the management of xerostomia.

Application of drug nanocrystal technologies on oral drug delivery of poorly soluble drugs

The limited solubility and dissolution rate exhibited by poorly soluble drugs is major challenges in the pharmaceutical process. Following oral administration, the poorly soluble drugs generally show a low and erratic bioavailability which may lead to therapeutic failure. Pure drug nanocrystals, generated by "bottom up" or "top down" technologies, facilitate a significant improvement on dissolution behavior of poorly soluble drugs due to their enormous surface area, which in turn lead to substantial improvement in oral absorption. This is the most distinguished achievement of drug nanocrystals among their performances in various administration routes, reflected by the fact that most of the marketed products based on the nanocrystals technology are for oral application. After detailed investigations on various technologies associated with production of drug nanocrystals and their in vitro physicochemical properties, during the last decade more attentions have been paid into their in vivo behaviors. This review mainly describes the in vivo performances of oral drug nanocrystals exhibited in animals related to the pharmacokinetic, efficacy and safety characteristics. The technologies and evaluation associated with the solidification process of the drug nanocrystals suspensions were also discussed in detail.

Development and in vitro characterization of insulin loaded whey protein and alginate microparticles

Insulin was encapsulated into microparticles (MP) made of denaturized whey proteins (WP) and alginate (ALG) using an extrusion/cold gelation process with calcium ions. High encapsulation efficiency of 85% was obtained. Influence of insulin on polymeric viscosity and on microparticle behavior was evaluated. Insulin seemed to interact with WP chains by non covalent binding and steric hindrance. This influence was balanced by ALG addition. Nevertheless, insulin was released rapidly by diffusion at both acidic and intestinal dissolution media. Despite this fast in vitro release, WP/ALG MP showed an important enzymatic inhibition effect on trypsin and alpha-chymotrypsin. Thus, WP/ALG MP contributed to an effective insulin protection towards enzymatic degradation. The aforementioned results suggested that WP based microparticles are a promising carrier for improving oral delivery of insulin.