Stability and Release Kinetics of an Advanced Gliclazide-Cholic Acid Formulation: The Use of Artificial-Cell Microencapsulation in Slow Release Targeted Oral Delivery of Antidiabetics

Introduction: In previous studies carried out in our laboratory, a bile acid (BA) formulation exerted a hypoglycaemic effect in a rat model of type-1 diabetes (T1D). When the antidiabetic drug gliclazide (G) was added to the bile acid, it augmented the hypoglycaemic effect. In a recent study, we designed a new formulation of gliclazide-cholic acid (G-CA), with good structural properties, excipient compatibility and exhibits pseudoplastic-thixotropic characteristics. The aim of this study is to test the slow release and pH-controlled properties of this new formulation. The aim is also to examine the effect of CA on G release kinetics at various pH values and different temperatures. Method: Microencapsulation was carried out using our Buchi-based microencapsulating system developed in our laboratory. Using sodium alginate (SA) polymer, both formulations were prepared: G-SA (control) and G-CA-SA (test) at a constant ratio (1:3:30), respectively. Microcapsules were examined for efficiency, size, release kinetics, stability and swelling studies at pH 1.5, pH 3, pH 7.4 and pH 7.8 and temperatures of 20 and 30 °C. Results: The new formulation is further optimised by the addition of CA. CA reduced microcapsule swelling of the microcapsules at pH 7.8 and pH 3 at 30 °C and pH 3 at 20 °C, and, even though microcapsule size remains similar after CA addition, percent G release was enhanced at high pH values (pH 7.4 and pH 7.8, p < 0.01). Conclusion: The new formulation exhibits colon-targeted delivery and the addition of CA prolonged G release suggesting its suitability for the sustained and targeted delivery of G and CA to the lower intestine

The applications of microencapsulated formulation of gliclazide and bile acids in Type-1 diabetes mellitus

Gliclazide is used in Type 2 diabetes (T2D) to stimulate insulin production but it also has beneficial extra-pancreatic effects which make it potentially useful in T1D. In this thesis, gliclazide was formulated with different bile acids, to enhance its effects, and formed microcapsules were examined in-vitro and in-vivo. In-vitro examinations of the microcapsules included complete characterization of the microcapsules in terms of interactions between gliclazide and a primary bile acid (chenodeoxycholic acid), a secondary bile acid (taurocholic acid) and a tertiary bile acid (ursodeoxycholic acid), and in-vitro release of gliclazide from microcapsules, while in-vivo examination of the microcapsules included gliclazide absorption and hypoglycemic and antiinflammatory effects in a rat model of T1D

IFN-γ production by splenocytes of mice immunised with Protein A and PBS by s/c and i/mam routes following stimulation with Protein A.

<p>IFN-γ production by splenocytes of mice immunised with Protein A and PBS by s/c and i/mam routes following stimulation with Protein A.</p

Detection of bacterial load and histopathological changes in the mammary glands of mice immunized with Protein A.

<p>Detection of bacterial load and histopathological changes in the mammary glands of mice immunized with Protein A.</p

Antigen-specific antibody isotypes of mice vaccinated with Protein A by s/c or i/mam routes.

<p>Antigen-specific antibody isotypes of mice vaccinated with Protein A by s/c or i/mam routes.</p

Experimental groups of mice used in the immunogenicity and protective potential trials of Protein A vaccines (n = 48).

<p>Experimental groups of mice used in the immunogenicity and protective potential trials of Protein A vaccines (n = 48).</p

Clinical signs observed in different groups of mice immunized with Protein A (Observations up to 5 days post challenge).

<p>Clinical signs observed in different groups of mice immunized with Protein A (Observations up to 5 days post challenge).</p

A comprehensive study of novel microcapsules incorporating gliclazide and a permeation enhancing bile acid: hypoglycemic effect in an animal model of Type-1 diabetes

Context: Gliclazide (G) is a commonly prescribed drug for Type 2 diabetes (T2D). In a recent study, we found that when G was combined with a primary bile acid, and gavaged to an animal model of Type 1 diabetes (T1D), it exerted a hypoglycemic effect. We hypothesized this to be due to metabolic activation of the primary bile acid into a secondary or a tertiary bile acid, which enhanced G solubility and absorption. The tertiary bile acid, taurocholic acid (TCA), has shown strong permeation-enhancing effects in vivo. Thus, we aimed to design, characterize, and test microcapsules incorporating G and TCA in an animal model of T1D. Methods: Microcapsules were prepared using the polymer sodium alginate (SA). G-SA microcapsules (control) and G–TCA–SA microcapsules (test) were extensively examined (in-vitro) at different pH and temperatures. The microcapsules were gavaged to diabetic rats, and blood glucose and G concentrations in serum were examined. Ex-vivo studies were also performed using a muscle cell line (C2C12), and cell viability and glucose intake post-treatment were examined. Results: G–TCA–SA microcapsules showed good stability, uniformity, and thermal and chemical excipient compatibilities. TCA did not change the size or the shape of the microcapsules, but it enhanced their mechanical resistance and reduced their swelling properties. G–TCA–SA enhanced the viability of C2C12 cells over 24 hours, and exerted a hypoglycemic effect in alloxan-induced type-1 diabetic rats. Conclusions: The incorporation of TCA into G-microcapsules resulted in functionally improved microcapsules with a positive effect on cell viability and glycemic control in Type-1 diabetic animals

Histopathological changes observed in mouse mammary tissue.

<p>Control mouse showing absence of inflammatory response (Level 0) in mammary tissue (A) to inoculation of sterile normal saline, H&E x100, bar, 200 μm (Fig 1a); Level 1 inflammatory response induced in the mouse teat by inoculation of <i>S</i>. <i>aureus</i> via the mammary duct (A), characterized by acute neutrophil rich response in the intraductal exudate, H&E x400, bar, 50 μm (Fig 1b); Level 2 inflammation of the mammary glands (A) Infiltrate of acute inflammatory cells, predominantly neutrophils, in supporting connective tissue, with intraluminal organisms, H&E x200, bar, 100 μm (Fig 1b); Level 2 inflammation of the mammary tissue post-inoculation of mammary gland with <i>S aureus</i>, characterized by infiltration of acute inflammatory cells, predominantly neutrophils (A), in supporting connective tissue and intraluminal space, H&E x200, bar, 100 μm (Fig 1c); Level 3 inflammation of mammary tissue post-inoculation of mammary gland with <i>S</i>. <i>aureus</i>, characterized by marked acute neutrophil rich infiltrate (A) with tissue necrosis (B), H&E x200, bar, 100 μm (Fig 1c); Level 3 inflammation of the mammary tissue post-inoculation of mammary gland with <i>S</i>. <i>aureus</i>, characterized by marked acute neutrophil-rich infiltrate (A) with tissue necrosis (B), H&E x200, bar, 100 μm (Fig 1d); Level 3 inflammation of the mammary tissue post-inoculation of mammary gland with <i>S</i>. <i>aureus</i>, characterized by neutrophil-rich inflammatory exudate, H&E x1000, bar, 20 μm (Fig 1e); Level 3 inflammation of the mammary tissue post-inoculation of mammary gland with <i>S</i>. <i>aureus</i>, characterized by presence of Gram-positive bacteria and neutrophil-rich inflammatory exudate, Gram Twort x400, bar, 50 μm (Fig 1f).</p

Detection of IL-1β and TNF-α levels in serum samples of mice 48 h post-infection.

<p>Detection of IL-1β and TNF-α levels in serum samples of mice 48 h post-infection.</p