pH- and ion-sensitive polymers for drug delivery

Abstract

Introduction Drug delivery systems (DDSs) are important for effective, safe, and convenient administration of drugs. pH- and ion-responsive polymers have been widely employed in DDS for site-specific drug release due to their abilities to exploit specific pH- or ion-gradients in the human body. Areas covered Having pH-sensitivity, cationic polymers can mask the taste of drugs and release drugs in the stomach by responding to gastric low pH. Anionic polymers responsive to intestinal high pH are used for preventing gastric degradation of drug, colon drug delivery and achieving high bioavailability of weak basic drugs. Tumor-targeted DDSs have been developed based on polymers with imidazole groups or poly(β-amino ester) responsive to tumoral low pH. Polymers with pH-sensitive chemical linkages, such as hydrazone, acetal, ortho ester and vinyl ester, pH-sensitive cell-penetrating peptides and cationic polymers undergoing pH-dependent protonation have been studied to utilize the pH gradient along the endocytic pathway for intracellular drug delivery. As ion-sensitive polymers, ion-exchange resins are frequently used for taste-masking, counterion-responsive drug release and sustained drug release. Polymers responding to ions in the saliva and gastrointestinal fluids are also used for controlled drug release in oral drug formulations. Expert opinion Stimuli-responsive DDSs are important for achieving site-specific and controlled drug release; however, intraindividual, interindividual and intercellular variations of pH should be considered when designing DDSs or drug products. Combination of polymers and other components, and deeper understanding of human physiology are important for development of pH- and ion-sensitive polymeric DDS products for patients.

Formulation and Pharmacokinetic Evaluation of Polymeric Dispersions Containing Valsartan

“…Eudragit E 100 is a cationic polymer with solubility in gastric fluid (pH up to 5.0) and gives pH-dependant drug release. Hence, in present work Eudragit E 100 is used to improve the solubility of weakly acidic drugs in the stomach at lower pH conditions [25,26]. Mixture of DCM and methanol were selected based on the solubility of drug and polymer.…”

Azo-Containing Polymers with Degradation On-Demand Feature

“…5,6 To achieve degradability, a variety of concepts have been investigated, including the introduction of chemically labile groups (such as esters or acetals), 7 the design of self-immolative polymers (which undergo depolymerization upon cleavage of stimuli-responsive end-groups), 8 the stimulidriven disassembly of supramolecular polymers, 2 the (dis)assembly of nanoparticles based on polymers exhibiting a lower critical solution temperature (LCST), 9 and the introduction of stimuli-responsive moieties that can be preferentially cleaved upon exposure to a specific stimulus or a combination thereof. 1,10 In addition to hydrolyzable or biodegradable motifs resulting from polycondensation, 1,7 the introduction of specific light-and heat-sensitive "weak links" has been broadly explored, e.g.…”

Wheat germ agglutinin anchored chitosan microspheres of reduced brominated derivative of noscapine ameliorated acute inflammation in experimental colitis

“…In this context, various approaches have been designed and developed to achieve the desired goals including timed release systems, pressure controlled systems, osmotically controlled systems, pH sensitive polymer coating, pro-drugs and bioresponsive microspheres [41]. Among these, pH dependent and colonic microflora responsive drug delivery systems revealed potential validated results that proved in clinical translation [42,43]. On the other hand, pressure controlled drug delivery systems have shown limited proofs [44].…”