PH-sensitive release

The gastrointestinal tract is known to possess a wide pH range, from a gastric pH of 1-2 to an intestinal tract pH of 7-8. Such significant changes could be utilized for the formation of pH-responsive drug delivery devices. Additionally, tumor sites and some sites of infection are known to have local acidic pH values amenable to pH-sensitive release methods. 

Obeidat WM, Price JC. Preparation and evaluation of Eudragit S 100 microspheres as pH-sensitive release preparations for piroxicam and theophylline using the emulsion-solvent evaporation method. Journal of Microencapsulation. March 2006 23(2) 195-202. PubMed PMID 16754375. 

Kumar S, Dory YL, Lepage M, Zhao Y (2011) Surface-grafted stimuli-responsive block copolymer brushes for the thermo-, photo-and pH-sensitive release of dye. Macromolecules 44 7385... 

KGM and acrylic acid crosslinked by N,N-methylene bis-(acrylamide) 5-aminosalicylic acid Hydrogel Swelling behavior and degradation process showed that the gel was pH sensitive. Release rate of the model drug 5-ASA was proven to be controlled by swelling and degradation processes. The accumulative release percent of 5-ASA reached 95.19% after 36 h. [103]... 

In a trial, microspheres of acrylamide-modified chitin were produced via ionically crosslinking with Fe3+ and then complexed with polycationic polysaccharide chito-san. The microspheres presented a fast responsive and pH-sensitive release behavior [101]. 

D. Liu, H. Hu, J. Zhang, X. Zhao, X. Tang, and D. Chen, Drug pH-sensitive release in vitro and targeting ability of polyamidoamine dendrimer complexes for tumor cells, Cheni Pharm Bull (Tokyo), 59 (1), 63-71, 2011. 

Delivery systems that respond to changes in pH have been known to the pharmaceutical industry for more than a century. The pH-sensitive enteric coating is probably the oldest controUed-release technology. Unna introduced an enteric tablet coating based on keratin in 1884 (108). Enteric coatings are used primarily to protect the gastric mucosa from local irritation or to ensure that tablets do not dissolve until they reach the intestine. 

Comparable daily doses of PPIs are omeprazole 20 mg = esomeprazole 20 mg = lansoprazole 30 mg = rabeprazole 20 mg = pantoprazole 40 mg. The PPIs degrade in acidic environments and are therefore formulated in delayed-release capsules or tablets.16 Lansoprazole, esomeprazole, and omeprazole contain enteric-coated (pH-sensitive) granules in a capsule form. For patients unable to swallow the capsule or in pediatric patients, the contents of the capsule can be mixed in applesauce or placed in orange juice. If a patient has a nasogastric tube, the contents of an omeprazole capsule can be... 

The pH-sensitive liposomes consist of mixtures of several saturated egg phosphatidylcholines and several A -acylamino acids. The release of drug is suggested to be a function of acid-base equilibrium effected by the interaction between ionizable amino acids and N-acy-lamino acid headgroups of the liposomes. There appears to be a close relation between Tc and pH effect [72],... 

A pH-sensitive gel, poly(AAc), was used as a coating on capsules containing insulin and surfactant. The capsules protected against insulin release in the upper gastrointestinal tract. As the pH increased to 7.5, drug release increased... 

Figure 3 Acetaminophen release from temperature- or pH-sensitive polymer NiPAAM/ BMA/DEAEMA at pH 2 and 7 and 37°C.

L-C Dong, AS Hoffman. A novel approach for preparation of pH-sensitive hydrogels for enteric drug delivery. J Controlled Release 15 141-152, 1991. 

Wang XL, Xu R, Lu ZR (2009) A peptide-targeted delivery system with pH-sensitive amphiphilic cell membrane disruption for efficient receptor-mediated siRNA delivery. J Control Release 134 207-213... 

Yuba E, Kojima C, Sakaguchi N, Harada A, Koiwai K, Kono K (2008) Gene delivery to dendritic cells mediated by complexes of lipoplexes and pH-sensitive fusogenic polymer-modified liposomes. J Control Release 130 77-83... 

Jiang and Zhu (2000) and Qiu and Zhu (2001) have reported the fabrication of multilayered devices composed of stacks of compression-molded disks of alternating compositions. One type of disk is either P(SA-EG) or P[SA-co-TMAgly)-Z>-EG] and the other is a pH-sensitive, protein-loaded blend of, for example, poly(methacrylic acid) and polyethoxazoline. The release of model proteins, myoglobin, bovine serum albumin, and FITC-dextran, and compounds such as brilliant blue have been studied and pulsatile release profiles have been demonstrated (Jiang and Zhu, 2000 Qiu and Zhu, 2001). 

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