Development and Characterization of N-Acetylcysteine-Conjugated PAMAM Dendrimers: Biophysical Evaluation of Their Interactions with Proteins and Drug Delivery Applications.

Poly(amidoamine) dendrimers (PAMAM) have been explored extensively for targeted drug delivery. Functionalization of the PAMAM dendrimer with N-acetyl cysteine (NAC) may reduce the toxicity associated with positively charged dendrimers and enable targeted delivery of cargo to the brain. In this research work, NAC-functionalized PAMAM G3.0 (NG3.0) and G4.0 (NG4.0) dendrimers were fabricated and characterized via 1H NMR, FTIR spectroscopy, dynamic light scattering, and atomic force microscopy, where the results confirmed the successful functionalization of NAC over the PAMAM surface. Further, interaction studies of NG3.0 and NG4.0 with proteins, i.e., bovine serum albumin and β-lactoglobulin, were performed using spectroscopic studies (fluorescence, UV-Visible, and circular dichroism spectroscopy). The study suggested that dendrimeric conjugates were adsorbed over the biomolecules through H-bonds and hydrophobic interactions, inducing partial conformational changes in the native protein structure while preserving the overall structural integrity of the proteins. The dendrimeric conjugates were further loaded with paclitaxel, and in vitro drug release studies were performed at pH 5.5 and pH 7.4, where the results showed 36.39 ± 3.20% and 28.73 ± 0.83% release for paclitaxel-loaded NG3.0 and NG4.0, respectively, at pH 7.4 after 6 h, while at acidic pH (5.5), 49.31 ± 1.69% and 46.62± 0.97% release were reported for paclitaxel-loaded NG3.0 and NG4.0 after 6 h, respectively. Cell line studies in a rat C6 glioma cell line suggested superior cellular uptake via energy-dependent endocytosis and clathrin-mediated pathway for the NAC-functionalized dendrimeric conjugates. The in vivo pharmacokinetic profile of paclitaxel-loaded NG4.0 demonstrated the sustained and elevated levels of drugs for an extended period following NAC conjugation. Our findings clearly show the efficacy of the NAC-functionalized PAMAM dendrimer, which is biocompatible and could efficiently carry and internalize payloads to glioma cells. Therefore, the paclitaxel-loaded dendrimeric conjugates may serve as a promising chemotherapeutic formulation, exhibiting better efficacy and lower toxicity.