Chitosan-Polyelectrolyte complexation for the preparation of gel beads and controlled release of anticancer drug. I. Effect of phosphorous polyelectrolyte complex and enzymatic hydrolysis of polymer

Abstract

Enzymic hydrolyzed chitosan was employed to prepare chitosan-tripolyphosphate and chitosan-polyphosphoric acid gel beads using a polyelectrolyte complexation method for the sustained-release of anticancer agent, 6-mercaptopurine (6-MP). pH responsive swelling ability, drug-release characteristics, and morphology of the chitosan gel bead depends on polyelectrolyte complexation mechanism and molecular weight of the enzymic hydrolyzed chitosan. The complexation mechanism of chitosan beads gelled in pentasodium tripolyphosphate or polyphosphoric acid solution was ionotropic crosslinking or interpolymer complex, respectively. The drug-release patterns of all chitosan gel beads in pH 6.8 seemed to be diffusional based, which might be in accordance with the Higuchi model, whereas release profiles of the chitosan-tripolyphosphate gel beads in pH 1.2 medium seemed to be non-Fickian diffusion controlled due to the swelling or matrix erosion of the beads. The rate of 6-MP releasing from chitosan-tripolyphosphate or chitosanpolyphosphoric acid gel matrix were significantly increased with the decreased molecular weight of enzymic hydrolyzed chitosan. However, the dissolution rates of 6-MP entraped in chitosan-tripolyphosphate and chitosan-polyphosphoric acid gel matrix were significantly slower than the dissolution rate of the original drug. These results indicate that the chitosan-polyphosphoric acid gel bead is a better polymer carrier for the sustained release of anticancer drugs in simulated intestinal and gastric juice medium than the chitosantripolyphosphate gel beads.

Desenvolvimento, caracterização e avaliação de sistemas microestruturados para veiculação de ácido retinóico na pele

“…Sistemas de liberação do tipo lipossomas para veiculação do ácido retinóico têm sido desenvolvidos por diversos autores até o momento (MONTENEGRO et al, 1996;BRISAERT et al, 2001;MANCONI et al, 2002;SHIMIZU et al, 2003;CONTRERAS et al, 2005;SINICO et al, 2005). Microemulsões tem sido o veículo de escolha utilizado por alguns autores (TROTTA et al, 2003;HUANG et al, 2004).…”

“…A separação e purificação das partículas obtidas podem ser feitas por filtração ou centrifugação seguida por lavagens sucessivas com água quente (KAWASHIMA et al, 1985). O TTP, ao contrário do glutaraldeído, que pode causar irritações às membranas mucosas devido a sua toxicidade, não é tóxico e forma gel por interação iônica entre os grupos aminos carregados positivamente da quitosana e os contra-íons do TTP (ARAL; AKBUGA, 1998;MI et al, 1999;ZHU, 2000ZHU, , 2001. BODMEIER et al (1989) relataram inicialmente a formação de complexos TTP-quitosana através do gotejamento da solução de quitosana numa solução de TTP.…”

“…A precisão de um método analítico é uma medida do erro aleatório entre as medidas efetuadas com a mesma amostra e pode ser expressa como a porcentagem do coeficiente de variação (% CV (MI et al, 1999;ZHU 2000ZHU , 2001). A figura 25 mostra as curvas termoanalíticas obtidas para o fármaco, o polímero, a mistura física e para as micropartículas.…”

Fabrication of Novel Porous Chitosan Matrices as Scaffolds for Bone Tissue Engineering

“…Chitosan microspheres were prepared by the ionotropic gelation of chitosan solution using tripolyphosphate ions as the crosslinking agent [13]. Briefly, chitosan (Sigma, St. Louis, MO) solutions in 1% (v/v) acetic acid with different concentration were added dropwise into a 10% (w/v) sodium tripolyphosphate solution separately through a 25 gauge (25G) needle by using a syringe pump (GENIE, Kent Scientific Corp., Torrington, CT) at a pumping rate of 20ml/hr.…”

Optimization of chlorpheniramine maleate (CPM) delivery by response surface methodology – four component modeling using various response times and concentrations of chitosan-alanine, glutaraldehyde and CPM

“…and fungal cell walls. It has been extensively studied as a carrier for drugs owing to its biocompatibility and biodegradability [1][2][3][4][5]. Chitosan based interpenetrating polymer networks (IPNs) currently received enormous interest for medical and pharmaceutical applications due to their good biocompatibility, low degradation and processing ease.…”