ABSTRACT
Scientists throughout the world are in search of novel modified biopolymer to fabricate smart drug delivery systems based on hydrogel formulations using several cross-linkers like glutaraldehyde, glyoxal, epichlorhydrin, adipic acid dihydrazide, carbodiimide, genipin, etc. Agents that are fused into the polymeric structure like isocyanates, glutaraldehyde, polyepoxides, etc., and are extremely toxic in nature. In addition, these are susceptible to percolate out into the body on biodegradation of polymeric structure. As an alternative to these toxic cross-linking agents, the periodate-Schiff base staining technique is widely being used for cross-linking in biology and biochemistry. The mechanism of this cross-linking technique is based on the reaction in-between the Schiff reagent and the aldehydes produced via the periodate oxidation. During the past few decades, several researchers have already been studied on the natural gums and also, developed their dialdehyde derivatives via the periodate oxidation technique. These periodate oxidized gums are being used to cross-link gelatin, other proteins and chitosan to develop various smart systems for drug delivery, tissue engineering, wound dressing, edible films, etc. The current review presents a comprehensive discussion of the available reported literature on the periodate oxidation of various gums and their use as natural cross-linker.
ABSTRACT
BACKGROUND: Metronidazole is often administered to patients with irritable bowel syndrome with an erroneous diagnosis of 'chronic amebiasis'. AIMS: To assess how patients with irritable bowel syndrome respond to metronidazole in the absence of amebae in their stools. METHODS: We randomly allocated 45 patients (35 men; aged 15-59 years) with irritable bowel syndrome to receive isapghul (10 g bid x 60 days), metronidazole (400 mg tid X 10 days, followed by placebo x 50 days), or placebo (1 capsule bid x 60 days). Symptoms were evaluated and scored on days 0, 15, 30, 45 and 60. Rectosigmoid manometry was performed in 5 of 15 patients in each group on days 0 and 60. RESULTS: There was a significant time effect and treatment effect on the symptom scores in all groups (isapghul > metronidazole > placebo); total score decreased from mean 25.8, 24.0 and 24.6 on day 0 to 7.2, 10.9 and 18.1 on day 60, respectively. Severity, duration and frequency of pain; and mucus in stool were all significantly reduced in all treatment groups (p < 0.001 for each). Treatment with isapghul increased the mean amplitude of propagated activity from 26.2 mmHg to 30.1 mmHg at 20 cm (p < 0.025) and from 23.1 mmHg to 27.4 mmHg at 10 cm (p < 0.05) from the anal verge, as well as the total duration of propagated activity at both sites (p < 0.05), with decrease in number of propagated contractions per 10 min (p < 0.025). Metronidazole and placebo had no effect on manometric findings. CONCLUSIONS: Metronidazole provides symptom relief in irritable bowel syndrome, without affecting rectosigmoid motility. This symptom response may be misinterpreted as supporting a diagnosis of 'chronic amebiasis'.