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Magnetic Fe 3 O 4 nanoparticles are gaining significance in drug delivery applications owing to their targeting capability. Surface modification of amphiphilic block polymers by Fe 3 O 4 nanoparticles increases their properties. In this study, Fe 3 O 4 @ PLGA-PEG nanocomposite is prepared by double emulsion (w/ o/w) method. A shift in the 2Θ values for the composite in XRD attributes to interaction between Fe 3 O 4 and PLGA-PEG. Also, a shift in the Fe-O band in the FTIR spectrum of Fe 3 O 4 @PLGA-PEG from 578 cm -1 to 510 cm -1 confirms the formation of nanocomposite. Surface morphology of the prepared nanocomposite is analyzed by TEM and AFM. Decrease in agglomeration due to electrostatic repulsion between the polymer chains and magnetic particles is observed while an increased surface area (61.0nm) confirms the formation of the nanocomposite. To determine the effectiveness of the prepared magnetically modified nanoparticles, methotrexate (anticancer drug) is encapsulated into the nanocomposite. High entrapment effi-ciency of 95% is observed when polymer:drug is 1:1. The invitro release profile shows that pH of release medium plays a significant role. At physiological pH of 7.3 there is only 15% methotrexate release while nearly 86% of methotrexate release is observed at acidic pH of 4.6 over 72h. Korsemeyer-Peppas model of drug release (R 2 -0.9868) represents swelling controlled release of methotrexate. Further, the cytotoxic cell viability assay on SK-BR-3 (breast adinocarcinoma) cells showed that methotrexate loaded onto the nanocomposite showed higher cell viability as compared to free methotrexate after 96h of incubation. The fluorescent cell imaging also showed that methotrexate released slowly from the nanoparticles and diffused into the nucleus without losing its cytotoxic effect on the cancer cells. Based on these properties of the magnetically modified PLGA-PEG nanoparticles they can be used as targeting drug delivery agents in treatment of cancer therapy.

The biophysical properties of DNA-modified Au nanoparticles (AuNPs) have attracted a great deal of research interest for various applications in biosensing. AuNPs have strong binding capability to the phosphate and sugar groups in DNA, rendering unique physicochemical properties for detection of metal ions. The formation of Au–DNA nanocomposites is evident from the observed changes in the optical absorption, plasmon band, zeta potential, DLS particle size distribution, as well as TEM and AFM surface morphology analysis. Circular dichroism studies also revealed that DNA-functionalized AuNP binding caused a conformational change in the DNA structure. Due to the size and shape dependent plasmonic interactions of AuNPs (33–78 nm) with DNA, the resultant Au–DNA nanocomposites (NCs) exhibit superior fluorescence emission due to chemical binding with Ca2+, Fe2+ and Mg2+ ions. A significant increase in fluorescence emission (λex = 260 nm) of Au–DNA NCs was observed after selectively binding with Mg2+ ions (20–800 ppm) in an aqueous solution where a minimum of 100 ppm Mg2+ ions was detected based on the linearity of concentration versus fluorescence intensity curve (λem = 400 nm). The effectiveness of Au–DNA nanocomposites was further verified by comparing the known concentration (50–120 ppm) of Mg2+ ions in synthetic tap water and a real life sample of Gelusil (300–360 ppm Mg2+), a widely used antacid medicine. Therefore, this method could be a sensitive tool for the estimation of water hardness after careful preparation of a suitably designed Au–DNA nanostructure.

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