SERS-assisted multivariate data analysis of the spectinomycin-Cu(ii) complex released in blood serum from a stimuli-responsive drug carrier: in vitro kinetics modeling and pharmacodynamic analysis

Controlled drug delivery from stimuli-responsive drug carriers offers effective therapeutic potential; however, the precise assessment of the release kinetics and pharmacodynamic (PD) behavior remains challenging. In this work, surface-enhanced Raman spectroscopy (SERS) is used to quantify the spectinomycin-copper (SPM-Cu(ii)) complex released in vitro into the human blood serum. Silver nanoparticles (AgNPs) are prepared by the chemical reduction method as the active SERS substrate. The SPM-Cu(ii) complex loaded on the stimuli-responsive PVA/AgO hydrogel is released into the blood serum, and the release kinetics and in vitro pharmacodynamics are studied at different time points up to 36 hours (1 h, 4 h, 8 h, 12 h, 16 h, 20 h, 24 h, 28 h, 32 h and 36 h). For multivariate data analysis, principal component analysis (PCA) is used to qualitatively study the intensity-based variability, partial least squares regression (PLSR) is used to quantify the SPM-Cu(ii) complex release kinetics and hierarchical cluster analysis (HCA) is used to determine spectral variability and classify temporal release profiles. The release kinetics is additionally validated by UV-vis spectroscopic quantification and compared with that of the SPM-Cu(ii) complex released in a phosphate buffer solution of pH 7.4 at 37 °C. The in vitro release kinetics is determined using four kinetic models: zero-order, first-order, Higuchi, and Korsmeyer–Peppas models. It is shown by mathematical fitting that the release is dominated by Higuchi (R2 = 0.934 in serum and 0.944 in PBS) and Korsmeyer–Peppas models (n = 0.463, which is Fickian diffusion), indicating that the release is diffusion-controlled. The pharmacodynamic potential of the released SPM-Cu(ii) complex in blood serum is evaluated systematically by establishing its antibacterial activity, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) and by conducting biofilm assays against Pseudomonas aeruginosa and Enterococcus faecalis. The cytotoxicity against the human liver cancer cell line (HepG2) and hemolytic analysis are also performed to validate the release kinetics in blood serum. The results indicate the improved antibacterial and biocompatible properties of SPM-Cu(ii) released in the blood serum from the PVA/AgO hydrogel.