Injectable Biocompatible Hydrogels from Cellulose Nanocrystals for Locally Targeted Sustained Drug Release

Injectable hydrogels from biocompatible materials are in demand for tissue engineering and drug delivery systems. Here, we produce hydrogels from mere cellulose nanocrystals (CNCs) by salt-induced charge screening. The injectability of CNC hydrogels was assessed by a combination of shear and capillary rheology, revealing that CNC hydrogels are conveyed via plug flow in capillaries allowing injection with minimal impact on mechanical properties. The potential of CNC hydrogels as drug carriers was elaborated by the in vitro release of the model protein bovine serum albumin (BSA), poorly water soluble tetracycline (TC), and readily soluble doxorubicin (DOX) into physiological saline and simulated gastric juice. For TC, a burst release was observed within 2 days, whereas BSA and DOX both showed a sustained release for 2 weeks. Only DOX was released fully from the hydrogels. The different release patterns were attributed to drug size, solubility, and specific drug-CNC interactions. The biocompatibility of CNC hydrogels and maintained bioactivity of released DOX were confirmed in a HeLa cell assay. The drug release was modulated by the incorporation of sucrose or xanthan gum in CNC hydrogels, whereas altering CNC concentration showed minor effects. The release into simulated gastric juice at pH 2 ceased for BSA due to charge inversion and electrostatic complexation, but not for smaller TC. Thus, CNC hydrogels may act as pH-responsive delivery systems that preserve drugs under gastric conditions followed by pH-triggered release in the duodenum.

Accurate and sensitive determination of sildenafil, tadalafil, vardenafil, and avanafil in illicit erectile dysfunction medications and human urine by LC with quadrupole-TOF-MS/MS and their behaviors in simulated gastric conditions

The widespread use of phosphodiesterase-5 inhibitors has attracted broad attention of counterfeiters to develop illicit erectile products with inaccurate amounts, unknown toxicity, and purity of active ingredients. Correspondingly, intake of these products endangers consumer health and needs to be screened for precautionary actions to reduce this risk. Therefore, in this study, a sensitive and rapid analytical method has been developed for simultaneous determination of selected phosphodiesterase-5 inhibitors present in illicit erectile medications and human urine. Quantification of the analytes was performed by liquid chromatography coupled with quadrupole-time-of-flight tandem mass spectrometry system. The chromatographic separation was successfully achieved with a run period of 8 min. Low detection limits were obtained in the range of 1.63-9.81 ng/g with relative standard deviations below 7.72% obtained using the replicate measurements of lowest concentration in calibration plots. The analytical performance of the proposed method proved good linearity, low detection limits, good accuracy and precision with high percent recoveries for human urine samples. Developed method was successfully applied to real samples including four different brands of illicit erectile medications. The results obtained revealed the presence of high levels of sildenafil in analyzed samples. The behaviors of selected phosphodiesterase-5 inhibitors were also studied in simulated gastric conditions.