We present the impact of surface modifications on the magnetic resonance imaging (MRI) contrast enhancement abilities of gadolinium oxide nanoparticles. A series of gadolinium oxide nanoparticles surface-coated with polyols of different reductive abilities such as diethylene glycol (DEG), triethylene glycol (TEG), tetraethylene glycol (TeEG), and polyethylene glycol (PEG 200) were synthesized. Particle sizes of synthesized Gd2O3 nanoparticles were found to be in correlation with the chain length of glycol. An enhancement in the in vitro and ex vivo relaxivity of Gd2O3 nanoparticles was revealed with the increase in glycol chain length. Among the various nanosystems, PEG-Gd2O3 has the highest in vitro and ex vivo relaxivities and excellent biocompatibility as revealed from cellular cytotoxicity experiments. The enhancement in MR contrast with glycol chain length can be attributed to the increase in surface hydrophilicity, and its modulation can be exploited as a novel strategy for enhancing the MRI contrast of gadolinium-based contrast agents.

Metabolomics is an analytical approach to metabolism and involves quantitative and comparative analysis of low-molecular-weight metabolites in body fluids or cellular/tissues extracts. Owing to its ability to reveal disease-specific metabolic patterns or metabolic changes produced in response to a therapeutic intervention; it is gaining widespread applications virtually in all aspects of biomedical and pharmaceutical research pertaining to human healthcare management. It has also started playing a strategic role in pharmacological and toxicological research for evaluating therapeutic efficacy/safety of promising drug candidates either alone or in conjunction with other omics tools such as genomics, transcriptomics and proteomics. The metabolic profiling capabilities of nuclear magnetic resonance (NMR) spectroscopy along with pattern recognition methods have successfully been applied for identifying a diagnostic panel of biomarkers, evaluating drug efficacy/safety, screening toxicity and disease mechanism. Particularly, the interest in applying NMR-based metabolomics for the assessment of therapeutic efficacy and safety is increasing among drug researchers and drug regulators owing to its nondestructive, non-selective and minimal sample preparation requirement. On top of this, it offers the potential for high-throughput (i.e. >100 samples a day is attainable) and provides highly reproducible results. In this review, we will discuss some of the recent developments related to NMR based metabolomics followed by some recent literature examples to highlight its potential in (a) the evaluation of therapeutic efficacy and safety of lead discovery compounds, (b) monitoring disease status and recovery after treatment and (c) identification and evaluation of biomarkers of systemic/organ-specific toxicity. Additionally, the review will also highlight its role to facilitate clinical trial testing and improve post-approval drug monitoring.

Owing to the peculiar broad-spectrum antimicrobial activities of zinc oxide nanoparticles (ZnO NPs), we envisaged their use to treat bacterial/mycobacterial/fungal infections during peritoneal dialysis (PD) of end-stage renal failure patients. However, a recent study from our lab showed that ZnO-NPs cannot be employed for the same in their naked form owing to their rapid agglomeration. Also, the naked ZnO-NPs showed strong interaction with organic acids present in the PD fluid (i.e., lactate and citrate present abundantly in almost all biological fluids) resulting in the formation of bioconjugates. Here, we propose that the surface coating of ZnO NPs may inhibit the binding interactions of NPs with the constituents of PD fluid. Therefore, in this study, we have carried out the surface coating of ZnO NPs with polyethylene glycol (PEG) of different molecular weights, followed by the investigations of physicochemical properties of PEGylated ZnO NPs dispersed in PD fluid using nuclear magnetic resonance (NMR) spectroscopy, dynamic light scattering (DLS), transmission electron microscopy (TEM), and Fourier transform infrared (FT-IR) spectroscopy. The interaction of PEGylated ZnO NPs has also been studied separately in glucose and lactic acid which are the main constituents of PD fluid and in citric acid. Although the X-ray diffraction and TEM results infer the colloidal stability of PEGylated ZnO NPs in PD fluid, FT-IR, UV–vis, and nuclear magnetic resonance results revealed the binding interactions of PEGylated ZnO NPs with the PD constituents. PEGylated ZnO NPs also interact strongly with the lactic acid and citric acid, leading to agglomeration, as observed previously for uncoated ZnO NPs. Further, the antibacterial activities of bare and PEG-coated ZnO NPs dispersion in PD fluid have been studied. A reduction in the bacterial inhibition effect against Staphylococcus aureus and Escherichia coli was observed for both the bare and PEG-coated ZnO NPs dispersed in PD fluid, indicating that the complex nature of PD fluid counteract on the efficiency of these nanobiotics.