Modification of psyllium polysaccharides for use in oral insulin delivery

A spotlight on application of microwave-assisted modifications of plant derived polymers in designing novel drug delivery systems

Polymers are a fundamental part of numerous industries and can be conjugated with many other materials and components to have a vast array of products. Biomaterials have been extensively studied for their application in pharmaceutical formulation development, tissue engineering, and biomedical areas. However, the native form of many polymers has limitations concerning microbial contamination, susceptibility, solubility, and stability. Chemical or physical modifications can overcome these limitations by tailoring the properties of polymers to meet several requirements. The polymer modifications are interdisciplinary, cutting across conventional materials, physics, biology, chemistry, medicine, and engineering limitations. Microwave irradiation has become a well-established technique for a few decades to drive and promote chemical modification reactions. This technique allows ease of temperature and power control to perform the synthesis protocols efficiently. Additionally, microwave irradiation contributes to green and sustainable chemistry. In this contribution, microwave-assisted polymer modifications were described with a special focus on their application in developing several novel dosage forms.

Silver-containing polysaccharide-based tricomponent antibacterial fibres for wound care applications

OBJECTIVE

Polysaccharide-based biomaterials are extensively used in wound care healing due to their unique liquid absorption, gelling properties and biocompatibility properties. They play an important role in controlling infections of highly exuding hard-to-heal wounds. The main objective of this study was to develop silver-containing polysaccharide-based tricomponent antibacterial fibres for use in these complex wounds.

METHOD

The fibres were developed by coating silver-containing alginate and psyllium fibres with hydrolysed chitosan. Dope solution containing alginate, psyllium and silver carbonate was extruded into a coagulation bath containing calcium chloride and hydrolysed chitosan. The developed fibres were tested for liquid absorption, swelling and antibacterial properties against a control fibre (of alginate and psyllium).

RESULTS

The developed fibres showed comparatively better liquid absorption, gelling and antibacterial properties than the control fibres.

CONCLUSION

The study concluded that developed fibres could be a preferred choice for application on hard-to-heal wounds with high levels of exudate, to support infection control and faster healing.

Oral Administration of Salecan-Based Hydrogels for Controlled Insulin Delivery

We present an improved type of food gum (salecan) based hydrogels for oral delivery of insulin. Structural hydrogel formation was assessed with Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray diffraction. We found that the hydrogel modulus, morphology, and swelling properties can be controlled by varying the salecan dose during hydrogel formation. Insulin was introduced into the hydrogel using a swelling-diffusion approach and then further used a drug prototype. In vitro insulin release profiles demonstrated that the release of entrapped insulin was suppressed in acidic conditions but markedly increased at neutral pH. Cell viability and toxicity tests revealed that the salecan hydrogel constructs were biocompatible. Oral administration of insulin-loaded salecan hydrogels in diabetic rats resulted in a sustained decrease of fasting plasma glucose levels over 6 h postadministration. For nondiabetic animals, the relative pharmacological bioavailability of insulin was significantly larger (6.24%, p < 0.05) for insulin-loaded hydrogels compared to free insulin. These results encourage further development of salecan-based hydrogels as vehicles for controlled insulin delivery following oral administration.

A review of biodegradable polymeric systems for oral insulin delivery

Currently, repeated routine subcutaneous injections of insulin are the standard treatment for insulin-dependent diabetic patients. However, patients' poor compliance for injections often fails to achieve the stable concentration of blood glucose. As a protein drug, the oral bioavailability of insulin is low due to many physiological reasons. Several carriers, such as macromolecules and liposomes have been used to deliver drugs in vivo. In this review article, the gastrointestinal barriers of oral insulin administration are described. Strategies for increasing the bioavailability of oral insulin, such absorption enhancers, enzyme inhibitors, enteric coatings are also introduced. The potential absorption mechanisms of insulin-loaded nanoparticles across the intestinal epithelium, including intestinal lymphatic route, transcellular route and paracellular route are discussed in this review. Natural polymers, such as chitosan and its derivates, alginate derivatives, γ-PGA-based materials and starch-based nanoparticles have been exploited for oral insulin delivery; synthetic polymers, such as PLGA, PLA, PCL and PEA have also been developed for oral administration of insulin. This review focuses on recent advances in using biodegradable natural and synthetic polymers for oral insulin delivery along with their future prospects.

Microwave-assisted synthesis of carboxymethyl psyllium and its development as semi-interpenetrating network with poly(acrylamide) for gastric delivery

In this study, microwave-induced synthesis of carboxymethyl psyllium is reported. The carboxymethyl psyllium was characterized by Fourier transform infrared, X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, and proton nuclear magnetic resonance spectroscopic analysis. It also showed fair antibacterial activity against model bacteria Escherichia coli, thus confirming its bioactivity. Its semi-interpenetrating polymer network hydrogels with poly(acrylamide) were synthesized and investigated for their swelling behavior in simulating gastric fluid at 37°C. The swelling ratio strongly depended on the degree of cross-linking and ratio of psyllium to acrylamide in the feed mixture. The kinetic water uptake data were interpreted by various kinetic models, and the order of fitness for these models was as follows: Power model > First-order model ≈ Schott model.

Effects of structural modifications on physicochemical and bile acid-binding properties of psyllium

The effects of sulfation, hydroxypropylation, and succinylation on gelling, water uptake, swelling, and bile acid-binding capacities of psyllium were examined and compared at the same molar substitution degree. Sulfated, hydroxypropylated, and succinylated psyllium were prepared with substitution levels of 1.02, 0.88, and 0.79, respectively, and their structures were characterized using FT-IR, SEM, and ζ-potential determination. All three derivatization methods reduced the gelling and swelling capacities of psyllium and increased the water uptake and bile acid-binding capacities compared to the original psyllium. Interestingly, it was observed for the first time that introduction of a stronger negatively charged group into the molecule might more effectively enhance the bile acid-binding capacity of psyllium. On the other hand, the steric effect of the substitution groups seemed to be more critical in altering the gelling and swelling properties of psyllium.

Pharmaceutical applications of various natural gums, mucilages and their modified forms

A large number of plant based pharmaceutical excipients are available today. Gums and mucilages are the most commonly available plant ingredients with a wide range of applications in pharmaceutical and cosmetic industries. They are being used due to their abundance in nature, safety and economy. They have been extensively explored as pharmaceutical excipients. They are biocompatible, cheap and easily available. Natural materials have advantages over synthetic ones since they are chemically inert, nontoxic, less expensive, biodegradable and widely available. They can also be modified in different ways to obtain tailor-made materials for drug delivery systems and thus can compete with the available synthetic excipients. Recent trend toward the use of plant based and natural products demands the replacement of synthetic additives with natural ones. In this review, we describe the pharmaceutical applications of various natural gums, mucilages and their modified forms for the development of various drug delivery systems.

Insulin nanoparticles for transdermal delivery: preparation and physicochemical characterization and in vitro evaluation

AIM

This work is aimed to study the feasibility of insulin nanoparticles for transdermal drug delivery (TDD) using supercritical antisolvent (SAS) micronization process.

METHODS

The influences of various experimental factors on the mean particle size (MPS) of insulin nanoparticles were investigated. Moreover, the insulin nanoparticles obtained were characterized by scanning electron microscopy (SEM), dynamic light scattering (DLS), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and thermogravimetric (TG) analyses.

RESULTS

Under optimum conditions, uniform spherical insulin nanoparticles with a MPS of 68.2 +/- 10.8 nm were obtained. The Physicochemical characterization results showed that SAS process has not induced degradation of insulin. Evaluation in vitro showed that insulin nanoparticles were accorded with the Fick's first diffusion law and had a high permeation rate.

CONCLUSION

These results suggest that insulin nanoparticles can have a great potential in TDD systems of diabetes chemotherapy.

Effects of hydroxypropylation on the functional properties of psyllium

The hydroxypropylated psyllium derivatives were successfully prepared with propylene oxide under the alkaline condition for the first time. Four hydroxypropylated psyllium derivatives, denoted as HP1, HP2, HP3, and HP4, were characterized for their hydroxypropyl content, molar substitution, and IR spectra. The hydroxypropyl derivatives were also evaluated for their surface structure, gelling properties, water uptake capacities, swelling volumes, and in vitro bile acid-binding abilities. The results showed that hydroxypropylation significantly reduced the gelling properties of psyllium. Psyllium derivatives with a relatively low hydroxypropyl substitution degree had greater in vitro binding capacities against cholic and chenodeoxycholic acids and higher swelling ability. The results from this study suggested that hydroxypropylation may be a possible approach for obtaining novel psyllium derivatives with improved physicochemical, functional, and biological properties for utilization in functional foods or supplemental and pharmaceutical products.

Effects of sulfation on the physicochemical and functional properties of psyllium

The sulfation of psyllium was carried out with sulfur trioxide-pyridine in dimethyl formamide. Three sulfated psyllium derivatives, named SP1, SP2, and SP3, were characterized by sulfur content determination, elemental analysis, FT-IR, and surface charge analysis. The sulfated derivatives were also evaluated for their morphological and rheological properties, water uptake capacities, swelling volumes, and in vitro bile acid-binding abilities. The results showed that sulfation reduced the gelling capacity of psyllium and the viscosity of its solution, and significantly increased its bile acid-binding capacity. Sulfation might also increase the water uptake ability of psyllium but might decrease its swelling capacity. The three sulfated psyllium derivatives had in vitro binding capacities against cholic and chenodeoxycholic acids comparable to that of cholestyramine resin on a per same as it is weight basis. The bile acid-binding capacity of SP1 was about 8.4-fold of that observed for the original psyllium preparation under the same assay conditions. The results from this study suggest that sulfation is a possible approach to obtain novel psyllium derivatives with desirable physicochemical, functional, and biological properties for utilization in functional foods or supplemental and pharmaceutical products.

Polymeric plant-derived excipients in drug delivery

Drug dosage forms contain many components in addition to the active pharmaceutical ingredient(s) to assist in the manufacturing process as well as to optimise drug delivery. Due to advances in drug delivery technology, excipients are currently included in novel dosage forms to fulfil specific functions and in some cases they directly or indirectly influence the extent and/or rate of drug release and absorption. Since plant polysaccharides comply with many requirements expected of pharmaceutical excipients such as non-toxicity, stability, availability and renewability they are extensively investigated for use in the development of solid oral dosage forms. Furthermore, polysaccharides with varying physicochemical properties can be extracted from plants at relatively low cost and can be chemically modified to suit specific needs. As an example, many polysaccharide-rich plant materials are successfully used as matrix formers in modified release dosage forms. Some natural polysaccharides have even shown environmental-responsive gelation characteristics with the potential to control drug release according to specific therapeutic needs. This review discusses some of the most important plant-derived polymeric compounds that are used or investigated as excipients in drug delivery systems.