PH-responsive polymers in drug delivery

Schmaljohann D (2006) Thermo-and pH-responsive polymers in drug delivery. Adv Drug Deliv Rev 58 1655... 

A pH-sensitive polymer in drug delivery applications is different from other stimuli-responsive polymers that require external stimuli such as temperature and light. The pH-sensitive polymers can take advantage of variations (whether they occur naturally or under pathological conditions) of pH in the body. 

Abstract This chapter summarizes the properties and most representative applications of pH-responsive polymers in the biomedical field.The most common methodologies to synthesize pH-responsive polymers such as emulsion polymerization, group transfer polymerization, atom transfer radical polymerization and reversible addition-fragmentation chain transfer polymerization are described. This chapter also discusses the most important applications of pH-responsive polymers in drug and gene delivery and the use of these systems as biosensors, taking into account the chemical and physical properties of these smart polymer systems. 

Other applications of pH-responsive polymers for drug-delivery systems have also been explored such as the incorporation of fibroblast growth factors to improve angiogenesis in infracted myocardium (Garbem et al., 2011) the incorporation of ketoprofen for colon-targeted delivery (Kulkami et al., 2012) intracellular delivery of ovalbumin to dendritic cells (a class of cells intimately involved with adaptive immunity) (Hn et al., 2007) and for controlling drug release in nocturnal asthma treatment (Tran et al., 2013). 

Poly[(4-carboxylatophenoxy)(methoxyethoxyethoxy)phosphazene] copolymers of variable compositions were synthesized by Allcock [645] in 1996. These polymers were found to be soluble in alkaline solutions. When crosslinked (by y-rays or by addition of CaCl2 to the polymer solution) the resulting hydrogels were found able to contract or expand as a function of the pH of the solution and their utilization as pH-responsive materials for drug delivery systems could be envisaged. 

When it comes to the pH range of different gastrointestinal segments (pH 1-8), early studies concerning the use of cationic polymers in drug delivery focused on providing environmentally responsive dmg release for oral... 

Stimuli-responsive polymers are defined as polymers that undergo relatively large and abrupt physical or chemical changes in response to small external changes in the environmental conditions. It can provide a variety of applications for the biomedical fields, especially in drug delivery field. These stimuli could be classified as either physical or chemical stimuli. Chemical stimuli, such as pH, ionic factors and chemical agents, will change the interactions between polymer... 

B. Singh, G. Chauhan, S. Kumar, and N. Chauhan, Synthesis, characterization and swelling responses of pH sensitive psyllium and polyacrylamide based hydrogels for the use in drug delivery (I), Carbohydr. Polym., 67 (2), 190-200,2007. 

Recently, there have been many investigations of stimuli-responsive hydrogels, which are three-dimensional polymer networks exhibiting sensitive swelling transitions dependent on various stimuH, e.g. electric field, pH, temperature, ionic strength or other chemicals. They have been considered to be useful in separation and medical applications, especially in drug delivery systems. 

In the future it will be necessary for further interdisciplinary work combining the approaches of chemical engineering, biology and material science to develop stimuli-responsive materials and their range of applications, particularly in terms of cellular therapies and regenerative medicine. pH-respon-sive polymers may well be suited to applications in drug delivery for clinical therapies and the manipulation of cells including neuronal and stem cells. 

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