In vitro and in vivo theophylline release from cellulose/chondroitin sulfate hydrogels

Biocompatible and biodegradable alginate/poly(N‐isopropylacrylamide) hydrogels for sustained theophylline release

“…As it is known, the swelling degree and the mesh size of a hydrogel have a major influence on the drug loading capacity thus it was expected the obtaining of a better drug entrapment (73%) within the sample with a higher hydrophylic alginate content, which was demonstrated to exhibit the highest swelling capacity and enhanced porosity compared with the other samples . These results are in agreement with those obtained by NIR investigations performed on other theophylline‐loaded hydrogels …”

“…A decrease of the theophylline percent released was recorded: total release (100%) from the 99/1/T composition in only the first 320 min to 92% from 75/25/T at 600 min. PNIPAAm/ALG hydrogel samples with compositions 80/20/T and 75/25/T reached the 100% theophylline released after 24 h. This behavior can be explained by the effect of the enhanced swelling capacity of the highly absorbent hydrogels and of the presence of hydrogen bonding interactions between the loaded drug and the polymeric matrix on the drug release rate by leading to a slower release rate and smaller released amount of drug and therefore on the ability to control drug release characteristics, as other studies have shown . By increasing the amount of hydrophilic alginate in the matrice composition the theophylline release rate decreased, this behavior being well correlated with the swelling capacity of these samples that can be attributed to the increased diffusion pathway created by the electrostatic repulsion among free ionized carboxylic acid groups in ALG and moreover because of some drug‐matrix interactions through hydrogen bonding occurring in these hydrogels with higher amount of ALG in composition, leading to a slower release rate and a smaller released amount before 600 min, thus a retarded drug release.…”

“…For the in vivo experiments the drug loading was performed by a diffusion filling method allowing the equilibrium partitioning of drug into the hydrogel from a solution of 4 wt % drug concentration in ethanol/water 1/1 mixture which swells the polymer network. The drug‐loaded hydrogels were prepared as suspensions, by swelling ∼0.1 g of PNIPAAm/ALG hydrogel in powder form in the 4 wt % theophylline solution (1:1, v/v, ethyl alcohol/water) under mild stirring for 24 h, period corresponding to the time necessary for all compositions to reach their equilibrium swelling degree, as determined from the swelling studies …”

“…Up to now, after our knowledge, previous studies performed using theophylline as model drug emphasized mainly on the in vitro and/or in vivo release experiments, the specific properties of the drug‐loaded matrices being overlooked. Therefore the physicochemical characteristics of the theophylline‐loaded samples including structure, morphology, drug‐polymeric matrix interactions and thermal behavior were investigated.…”

Preparation, Characterization and In vitro Evaluation of Theophylline Nanoparticles Prepared with Dextran- Conjugated Soy Protein

“…For years now, controlled delivery of bioactive agents has remained a major focus of pharmaceutical formulation research due to their relative permeability, robustness and short recovery after stress or damage that are related to mucous membrane [1]. The typical controlled delivery system shows a pattern of bioactive release, in which the bioactive concentration is maintained in the therapeutic window for a long enough period of time, thereby ensuring sustained physiological benefits.…”