Preparation and characterization of N-isopropylacrylamide/carboxymethylated chitosan hydrogel

Poly （N-isopropylacrylamide） （PNIPAAm）/carboxymethylated chitosan （CMCH） hydrogels were prepared by irradiating the aqueous solution mixture of NIPAAm and CMCH by 60 Co γ-ray.The effects of feed ratio of NIPAAm and CMCH,temperature,pH and ionic strength on the swelling ratio of PNIPAAm/CMCH hydrogels were studied.The results show that the addition of CMCH shifts the lower critical solution temperature （LCST） of the PNIPAAm hydrogel to higher temperature.The PNIPAAm/CMCH hydrogel displays not only pH-and thermo-sensitivity,but also ion-sensitivity.Differential scanning calorimetry （DSC） was applied for the determination of the LCST of the hydrogel.     

pH值敏感水凝胶的合成及药物缓释性能研究

聚乙二醇(PEG)与丙烯酰氯反应合成聚乙二醇双丙烯酸酯(PEGDA)，然后以PEGDA、N—乙烯基—2—此咯烷酮(NVP)及丙烯酸为主要原料，N，N^ —亚甲基双丙烯酰胺(BIS)为交联剂，偶氮二异丁腈(AIBN)为引发剂，采用自由基聚合法合成了对pH值变化敏感的N—乙烯基—2—吡咯烷酮—丙烯酸—聚乙二醇双丙烯酸酯交联共聚物(po1y[NVP-AA-PEGDA])水凝胶．利用该共聚物为载体对抗癌药5—氟脲密啶(5—FU)进行包埋，并在SIF及SGF缓冲溶液中于37℃进行体外释药研究．结果表明，在pH值较小的缓释介质中药物释放曲线较平缓，释药周期较长，同时最终的平衡释药百分数也较小；随着样品中PEGDA量的减少，释药曲线趋于平缓，释药周期变长，最终的平衡释药百分数成小．     

Amplification of urea detection based on pH-sensitive liposomes

BackgroundThis study aimed to develop an amplification method of urea detection based on pH-sensitive liposomes.ResultsThe urease covalently immobilized on the magnetic particles and the pH-sensitive liposomes encapsulating ferricyanide were added to the cyclic-voltammeter cell solution where urea was distributed. The conversion of urea into carbonic acid seemed to induce a pH decrease that caused a reduction in the electrostatic repulsion between the headgroups of weakly acidic 1,2-dipalmitoyl-sn-glycero-3-succinate. The reduction induced the liposomes to release potassium ferricyanide that was encapsulated inside. The effects of urea concentration and pH value were investigated. A specific concentration (0.5 mg/mL) of the urea solution was set to observe the response. The activity of urease was reversible with respect to the pH change between 7 and 5. The sensitivity of this detection was almost identical to the comparable techniques such as an enzyme-linked immunosorbent assay and a field-effect transistor.ConclusionsIn summary, the methodology developed in this study was feasible as a portable, rapid, and sensitive method.How to cite: Kang MK, Park J-W. Amplification of urea detection based on pH-sensitive liposomes. Electron J Biotechnol 2021;51. https://doi.org/10.1016/j.ejbt.2021.04.005