Degradability of the linear azo polymer conjugated 5,5′‐azodisalicylic acid segment in the main chain for colon‐specific drug delivery

Abstract

A novel type of linear copolymer composed of poly(ethylene glycol) (PEG) with 5, 5 0 -azodisalicylic acid [olsalazine (OLZ)] was developed for colon-specific drug delivery. These copolymers contained azo bonds that would be degraded by the azoreductase activities in the colon. The resultant condensation polymers were characterized with Fourier transform infrared, nuclear magnetic resonance, and gel permeation chromatography. The degradation behavior of the polymer was evaluated in vitro and in vivo. The in vitro results indicated that the active 5-aminosalicylic acid (5-ASA), one of the degradation products, could be released in the medium of the cecum contents specifically. In an in vivo test, there was a 8-h lag time before 5-ASA could be detected in urine samples, and this indicated that the conjugate could remain intact in the upper part of the gastrointestinal tract. In comparison with OLZ, the release profiles of 5-ASA from PEG-OLZ copolymers were significantly prolonged. In addition, the release profiles of 5-ASA from PEG-OLZ copolymers could be adjusted by changes in the molecular weight of the PEG segment. Because of these advantages of PEG-OLZ copolymers, it could be concluded that PEG-OLZ copolymers could be promising candidates for colon-specific polymeric prodrugs of 5-ASA.

Multistimuli Responsive Polymer Nanoparticles On the basis of the Amphiphilic Azobenzene-Contained Hyperbranched Poly(ether amine) (hPEA-AZO)

“…[1][2][3][4][5][6] The stimuli-responsive behaviors of polymer nanoparticles strongly depend on the external chemical and physical stimuli, such as ionic strength, light, electric and magnetic field, temperature and pH. [7][8][9] Because of the easycontrol, light-response is becoming of special importance to polymer nanoparticles in the application fields of drug delivery [10][11][12] and photo sensor. [13][14][15] To obtain the polymer nanopaticles response to light, a variety of light-responsive moieties are introduced into the polymers which construct polymer nanoparticles.…”

“…Because of their potential applications in separation, biosensor, chemical storage and transport, and gene and drug delivery, polymer nanoparticles with response to environmental stimuli have attracted much attention. − The stimuli-responsive behaviors of polymer nanoparticles strongly depend on the external chemical and physical stimuli, such as ionic strength, light, electric and magnetic field, temperature and pH. − Because of the easy-control, light-response is becoming of special importance to polymer nanoparticles in the application fields of drug delivery − and photo sensor. − To obtain the polymer nanopaticles response to light, a variety of light-responsive moieties are introduced into the polymers which construct polymer nanoparticles. Among these light-responsive moieties, azobenzene group is most studied due to its well-known reversible isomerization from trans- to cis- configuration upon irradiation. − Several research groups reported the responsive polymer nanoparticles formed by self-assembly of amphiphilic azobenzene-contained copolymers in aqueous solution. ,− Besides response to light, some of these polymer nanoparticles exhibited the response to another stimulus such as temperature , or pH .…”