Colonic Delivery of β‐Lactamases Does not Affect Amoxicillin Pharmacokinetics in Rats

Pectin based multi-particulate carriers for colon-specific delivery of therapeutic agents

In case of colon-specific delivery of therapeutic agents through oral route, microbial/enzyme-triggered release approach has several advantages over other approaches due to unique microbial ecosystem in the colon. Multiple-unit carriers have an edge over single-unit carriers for this purpose. Among different materials/polymers explored, pectin appears as a promising biopolymer to construct microbial-triggered colon-specific carriers. Pectin is specifically degraded by colonic enzymes but insusceptible to upper gastro-intestinal enzymes. In this article, utilization of pectin solely or in combination with other polymers and/or colonic-delivery approaches is critically discussed in detail in the context of multi-particulate systems. Several studies showed that pectin-based carriers can prevent the release of payload in the stomach but start to release in the intestine. Hence, pectin alone may construct delayed release formulation but may not be sufficient for effective colon-targeting. On the other hand, combination of pectin with other materials/polymers (e.g., chitosan and Eudragit® S-100) has demonstrated huge promise for colon-specific release of payload. Hence, smartly designed pectin-based multi-particulate carriers, especially in combination with other polymers and/or colon-targeting approaches (e.g., microbial-triggered + pH-triggered or microbial-triggered + pH-triggered + time-release or microbial-triggered + pH-triggered + pressure-based), can be successful colon-specific delivery systems. However, more clinical trials are necessary to bring this idea from bench to bedside.

Oral Beta-Lactamase Protects the Canine Gut Microbiome from Oral Amoxicillin-Mediated Damage

Antibiotics damage the gut microbiome, which can result in overgrowth of pathogenic microorganisms and emergence of antibiotic resistance. Inactivation of antibiotics in the small intestine represents a novel strategy to protect the colonic microbiota. SYN-004 (ribaxamase) is a beta-lactamase formulated for oral delivery intended to degrade intravenously administered beta-lactam antibiotics in the gastrointestinal (GI) tract. The enteric coating of ribaxamase protects the enzyme from stomach acid and mediates pH-dependent release in the upper small intestine, the site of antibiotic biliary excretion. Clinical benefit was established in animal and human studies in which ribaxamase was shown to degrade ceftriaxone in the GI tract, thereby preserving the gut microbiome, significantly reducing Clostridioides difficile disease, and attenuating antibiotic resistance. To expand ribaxamase utility to oral beta-lactams, delayed release formulations of ribaxamase, SYN-007, were engineered to allow enzyme release in the lower small intestine, distal to the site of oral antibiotic absorption. Based on in vitro dissolution profiles, three SYN-007 formulations were selected for evaluation in a canine model of antibiotic-mediated gut dysbiosis. Dogs received amoxicillin (40 mg/kg, PO, TID) +/- SYN-007 (10 mg, PO, TID) for five days. Serum amoxicillin levels were measured after the first and last antibiotic doses and gut microbiomes were evaluated using whole genome shotgun sequence metagenomics analyses of fecal DNA prior to and after antibiotic treatment. Serum amoxicillin levels did not significantly differ +/- SYN-007 after the first dose for all SYN-007 formulations, while only one SYN-007 formulation did not significantly reduce systemic antibiotic concentrations after the last dose. Gut microbiomes of animals receiving amoxicillin alone displayed significant loss of diversity and emergence of antibiotic resistance genes. In contrast, for animals receiving amoxicillin + SYN-007, microbiome diversities were not altered significantly and the presence of antibiotic resistance genes was reduced. These data demonstrate that SYN-007 diminishes amoxicillin-mediated microbiome disruption and mitigates emergence and propagation of antibiotic resistance genes without interfering with antibiotic systemic absorption. Thus, SYN-007 has the potential to protect the gut microbiome by inactivation of beta-lactam antibiotics when administered by both oral and parenteral routes and to reduce emergence of antibiotic-resistant pathogens.

Colon targeted beads loaded with pterostilbene: Formulation, optimization, characterization and in vivo evaluation

Background

Pterostilbene has a proven chemopreventive effect for colon carcinogenesis but suffers low bioavailability limitations and therefore unable to reach the colonic tissue.

Objective and methodology

To overcome the issue of low bioavailability, pterostilbene was formulated into an oral colon targeted beads by ionic gelation method using pectin and zinc acetate. Optimization was carried out by 2³ factorial design whereby the effect of pectin concentration (X₁), zinc acetate concentration (X₂) and pterostilbene:pectin ratio (X₃) were studied on entrapment efficiency (Y₁) and in vitro drug release till 24 h (Y₂). The optimized beads were characterized for shape and size, swelling and surface morphology. The optimized beads were uniformly coated with Eudragit S-100 using fluidized bed coater. Optimized coated beads were characterized for in vitro drug release till 24 h and surface morphology. Pharmacokinetic and organ distribution study were performed in rats to ascertain the release of pterostilbene in colon.

Results

The optimized formulation comprised of 2% w/v of pectin concentration (X₁), 2% w/v of zinc acetate concentration (X₂) and 1:4 of pterostilbene:pectin ratio (X₃), which showed a satisfactory entrapment efficiency (64.80%) and in vitro release (37.88%) till 24 h. The zinc pectinate beads exhibited sphericity, uniform size distribution, adequate swelling and rough surface. The optimized coated beads achieved 15% weight gain, displayed smooth surface and optimum drug release. Pterostilbene from optimized coated beads appeared in the plasma at 14 h and reached the C_max at 22 h (T_max), whereas plain pterostilbene exhibited T_max of 3 h.

Discussion and conclusion

Thus, larger distribution of pterostilbene was obtained in the colonic tissue compared to stomach and small intestinal tissues. Thus, delayed T_max and larger distribution of pterostilbene in colonic tissue confirmed the targeting of beads to colon.

Sustained Anti-inflammatory Effect of Resveratrol-Phospholipid Complex Embedded Polymeric Patch

Resveratrol-phospholipid complex (Phytosome®) (RSVP) was found better aqueous soluble and permeable than free resveratrol (RSV). RSVPs were incorporated in polymeric patch prepared by solvent casting method using Eudragit RL 100, PVP K30, and PEG 400 for application on dermal sites for sustained treating of inflammation. Prepared patches were evaluated for various physicochemical properties, surface morphology by SEM, TEM, and compatibility of patch components by FT-IR and DSC studies. Optimized formulation (F9) gave 95.79 ± 3.02% drug release and 51.36% (4.28 ± 0.48 mg/cm²) skin permeation after 24 h. Skin extract when examined for drug accumulation showed 38.31 ± 2.42% drug content. FE-SEM images of the patch taken after drug release and skin permeation studies showed that RSVPs in polymeric patch are stable and retain their structure after 24 h long exposure to physiologic environment. Sustained anti-inflammatory effect was established in carrageenan-induced paw edema model in which test formulation gave 84.10% inhibition of inflammation at 24 h as compared to 39.58% for standard diclofenac sodium gel. The CLSM study confirmed the localization of RSVPs for a longer period, thus enabling drug targeting to the dermis for sustained effect. Skin irritation test on rabbit revealed that the patches are safe for skin application. Histological observations suggested that after exposure to the permeants, the SC integrity had not altered and no evidence of presence of inflammatory cells found. RSVP (Phytosome®) containing patches abled to give sustained therapeutic effect that may be useful in treating acute and chronic inflammation.

Gastrointestinal colonization with a cephalosporinase-producing bacteroides species preserves colonization resistance against vancomycin-resistant enterococcus and Clostridium difficile in cephalosporin-treated mice

Antibiotics that are excreted into the intestinal tract may disrupt the indigenous intestinal microbiota and promote colonization by health care-associated pathogens. β-Lactam, or penicillin-type, antibiotics are among the most widely utilized antibiotics worldwide and may also adversely affect the microbiota. Many bacteria are capable, however, of producing β-lactamase enzymes that inactivate β-lactam antibiotics. We hypothesized that prior establishment of intestinal colonization with a β-lactamase-producing anaerobe might prevent these adverse effects of β-lactam antibiotics, by inactivating the portion of antibiotic that is excreted into the intestinal tract. Here, mice with a previously abolished microbiota received either oral normal saline or an oral cephalosporinase-producing strain of Bacteroides thetaiotaomicron for 3 days. Mice then received 3 days of subcutaneous ceftriaxone, followed by either oral administration of vancomycin-resistant Enterococcus (VRE) or sacrifice and assessment of in vitro growth of epidemic and nonepidemic strains of Clostridium difficile in murine cecal contents. Stool concentrations of VRE and ceftriaxone were measured, cecal levels of C. difficile 24 h after incubation were quantified, and denaturing gradient gel electrophoresis (DGGE) of microbial 16S rRNA genes was performed to evaluate the antibiotic effect on the microbiota. The results demonstrated that establishment of prior colonization with a β-lactamase-producing intestinal anaerobe inactivated intraintestinal ceftriaxone during treatment with this antibiotic, allowed recovery of the normal microbiota despite systemic ceftriaxone, and prevented overgrowth with VRE and epidemic and nonepidemic strains of C. difficile in mice. These findings describe a novel probiotic strategy to potentially prevent pathogen colonization in hospitalized patients.

Efficacy and pharmacological mechanism of pronase-enhanced low-dose antibiotics for Helicobacter pylori eradication

This study examined the efficacy and pharmacological mechanism of pronase-assisted low-dose antibiotics for eradication of Helicobacter pylori. Mongolian gerbils infected with H. pylori received 7-day treatment (omeprazole, different concentrations of pronase, amoxicillin, and clarithromycin), and the efficacy was assessed using the eradication rate and the colonization of H. pylori. In Mongolian gerbils orally administered pronase, the thickness of the gastric mucous layer (GML) was examined using immunohistochemical and alcian blue staining, and the concentrations of amoxicillin in gastric tissue and serum were detected using high-performance liquid chromatography (HPLC). The eradication rates were 80.0% (12/15) in the high-pronase quadruple group (HPQG) and 86.7% (13/15) in the high-antibiotic group (HAG) (P = 1.000). The antibiotic dose in the HPQG was only 1/20 that in the HAG. Thirty minutes after oral treatment with pronase, the sticky protein of the GML was hydrolyzed, and the GML became thinner. Higher amoxicillin concentrations in both the gastric tissue and serum were observed in the pronase group than in the Am10 group. The concentration of amoxicillin in the Am10-plus-Pr108 group in gastric tissue was 3.8 times higher than in the Am10 group in 5 min. Together, these data suggest that pronase significantly reduced the dose of antibiotics used in H. pylori eradication. The pharmacological mechanism is likely pronase removal of the mucus layer, promoting chemical factor (i.e., gastric acid and pepsinogen) distribution and increasing the antibiotic concentrations in the deep GML, which acted on H. pylori collectively. Thus, pronase may enhance the level of antibiotics for eradication of H. pylori in the clinic.

Impact of glutaraldehyde on in vivo colon-specific release of resveratrol from biodegradable pectin-based formulation

Despite potential therapeutic efficacy of resveratrol on colitis and colorectal cancer, rapid absorption and metabolism at the upper gastro-intestinal (GI) tract prevent its clinical application. To overcome this, we attempted to develop colon-specific multi-particulate calcium-pectinate (Ca-pectinate) formulations of resveratrol. However, they were unable to prevent premature drug release at the upper GI tract. Thus, glutaraldehyde (Glu) was used for further cross-linking of the pectin chains. The formulation conditions and procedure were optimized from the in vitro drug release study. The optimized formulation was subjected to in vivo pharmacokinetic study in rats and compared with the unmodified Ca-pectinate and suspension formulation of resveratrol. Spherical particles (∼1 mm diameter) with high drug encapsulation were produced. Low cross-linking solution pH (1.5), minimum Glu concentration (2.5%) and cross-linking time (2 h) were crucial to exhibit colon-specific drug release. As Glu was added in the cross-linking solution, cross-linking between pectin chains and Glu occurred simultaneously during Ca-pectinate network formation, which appeared as a cost-effective formulation technique. Most importantly, the pharmacokinetic study demonstrated in vivo colon-specific drug release from the optimized formulation, while faster drug release was observed from the unmodified and suspension formulations. Hence, the developed formulation has potential to be used as colon-specific delivery system of resveratrol.

Formulation and optimization of zinc-pectinate beads for the controlled delivery of resveratrol

Preventive and therapeutic efficacies of resveratrol on several lower gastrointestinal (GI) diseases (e.g., colorectal cancer, colitis) are well documented. To overcome the problems due to its rapid absorption and metabolism at the upper GI tract, a delayed release formulation of resveratrol was designed to treat these lower GI diseases. The current study aimed to develop a delayed release formulation of resveratrol as multiparticulate pectinate beads by varying different formulation parameters. Zinc-pectinate (Zn-pectinate) beads exhibited better delayed drug release pattern than calcium-pectinate (Ca-pectinate) beads. The effects of the formulation parameters were investigated on shape, size, Zn content, moisture content, drug encapsulation efficiency, swelling-erosion, and resveratrol retention pattern of the formulated beads. Upon optimization of the formulation parameters in relative to the drug release profiles, the optimized beads were further subjected to morphological, chemical interaction, enzymatic degradation, and stability studies. Almost all prepared beads were spherical with approximately 1 mm diameter and efficiently encapsulated resveratrol. The formulation parameters revealed great influence on resveratrol retention and swelling-erosion behavior. In most of the cases, the drug release data more appropriately fitted with zero-order equation. This study demonstrates that the optimized Zn-pectinate beads can encapsulate very high amount of resveratrol and can be used as delayed release formulation of resveratrol.

Resveratrol-loaded calcium-pectinate beads: effects of formulation parameters on drug release and bead characteristics

Resveratrol has potential therapeutic efficacy on several lower gastro-intestinal (GI) diseases such as colitis and colorectal cancer. But resveratrol is quickly absorbed and metabolized at the upper GI tract, which renders it unsuitable for this purpose. This study aimed at devising a delayed release formulation of resveratrol as calcium-pectinate (Ca-pectinate) beads and investigated the impact of various formulation parameters on bead characteristics. Ca-pectinate beads were prepared by varying six formulation parameters (cross-linking pH, cross-linker concentration, cross-linking time, drying condition, pectin concentration, and resveratrol concentration). Their effects were investigated on calcium entrapment, moisture content and weight loss during drying, particle shape and size, resveratrol entrapment and loading efficiency, swelling-erosion, and resveratrol retention pattern of formulated beads. Preparative conditions were optimized from these studies and optimized beads were further subjected to morphological examination, drug-polymer interaction, and enzymatic degradation study. Almost all prepared beads were spherical with approximately 1 mm diameter. Swelling-erosion and drug retention pattern were changed with formulation variables. Release data of almost all beads showed linearity of the plots for the cumulative percent resveratrol released versus square root of time often after an initial lag period. Observations from the present study revealed that optimized Ca-pectinate beads can encapsulate a very high amount of resveratrol (>97.5%) and can be used for delayed release and site-specific delivery to the lower GI tract. Depending on the formulation parameters, release of resveratrol after 10 h incubation in the intestinal media was 80-100%.

Removal of ciprofloxacin in simulated digestive media by activated charcoal entrapped within zinc-pectinate beads

Beads made of a zinc-pectinate matrix containing activated charcoal were designed for the adsorption of colonic residual antibiotics responsible of the emergence of resistance. Bead stability was shown to correlate with bead zinc content, 0.08 mg/mg being the minimal amount of zinc that protects the egg-box structure against total disintegration. Moreover, the stability in simulated gastro-intestinal media was shown to be related to the composition of the incubation medium. Indeed, gastric medium was shown to extract a large amount of zinc inducing an early disintegration of the beads in the intestinal medium, making necessary their protection by gastro-resistant capsules. Simulated intestinal medium buffered by phosphate was not adapted for the disintegration studies since the formation of a zinc phosphate precipitate on beads surface enhances their resistance to further degradation by pectinases contained in colonic medium. On the other hand, beads incubated in HEPES were stable in intestinal medium and nicely degraded by pectinases contained in simulated colonic medium. Despite this stability, coating with Eudragit RS was needed to prevent the early adsorption of antibiotics in intestinal medium. Adsorption studies in the simulated colonic medium show that the adsorption capacity of activated charcoal is not modified after its encapsulation within pectin beads making the elimination of ciprofloxacin reaching the colon clinically feasible.