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The influence of nanoparticles inside the human body and their interactions with biological macromolecules need to be explored/studied prior to specific applications. The objective of this study is to find the potential of camptothecin functionalised silver nanoparticles (CMT-AgNPs) in biomedical applications. This article primarily investigates the binding stratagem of CMT-AgNPs with calf thymus DNA (ctDNA) through a series of spectroscopic and calorimetric methods and then analyses the anticancer activity and cytotoxicity of CMT-AgNPs. The nanoparticles were synthesized using a simple one pot method and characterized using UV–Visible, fourier transform infrared (FTIR) spectroscopy, X-ray diffraction and high-resolution transmission electron microscopy (HRTEM). The average size of CMT-AgNPs is 10 ± 2 nm. A group of experimental techniques such as UV–Visible spectrophotometry, fluorescence dye displacement assay, circular dichroism (CD) and viscosity analysis unravelled the typical groove binding mode of CMT-AgNPs with ctDNA. The CD measurement evidenced the minor conformational alterations of double helical structure of ctDNA in the presence of CMT-AgNPs. The information deduced from the isothermal titration calorimetry (ITC) experiment is that the binding was exothermic and spontaneous in nature. Moreover, all the thermodynamic binding parameters were extracted from the ITC data. The binding constants obtained from UV absorption experiments, fluorescence dye displacement studies and ITC were consistently in the order of 104 Mol−1. All these results validated the formation of CMT-AgNPs–ctDNA complex and the results unambiguously confirm the typical groove binding mode of CMT-AgNPs. An exhaustive in vitro MTT assay by CMT-AgNPs and CMT against A549, HT29, HeLa and L929 cell lines revealed the capability of CMT-AgNPs as a potential anticancer agent. [ABSTRACT FROM AUTHOR]

Vibrational state side-band spectral analysis of silica matrices, doped with ZnSe/[Eu.sup.3+] ions, associated with the excitation transition [sup.7][F.sub.0] → [sup.5][D.sub.2] is used to analyze the local asymmetry of the rare earth ions in the glass host. The large inhomogeneous linewidth for the ZnSe co-doped samples indicates the wide distribution of the [Eu.sup.3+] ions in the matrix and is related to the flexibility of the local glass network. The fluorescence spectra reveal that the intensity of the characteristic emission of europium increases considerably in the presence of ZnSe particles. This phenomenon can be explained by the energy transfer resulting from electron-hole recombination in the ZnSe to the rare earth ion. Nonlinear optical absorption of the sample is also investigated at a wavelength of 532 nm, using open aperture Z-scan technique. The sample exhibits reversible saturable absorption (RSA), which is found to depend on excitation fluence. RSA is due to the enhanced absorption resulting from the electron dynamics in nano-crystallites. PACS Nos: 78, 79, 81 Nous utilisons une analyse spectrale de la bande lateerale de l'etat vibrationnel dans une matrice de silice dopee aux ions ZnSe/[Eu.sup.3+] associeea l'excitation de transition [sup.7][F.sub.0]?[sup.5][D.sub.2], afin d'analyser l'asymetrie locale des ions de terre rare dans le verre hote. La grande largeur de bande inhomogene pour les echantillons dopes de ZnSe indique une large distribution des ions [Eu.sup.3+] dans la matrice et est relieeea la flexibilite du reseau de verre local. Le spectre de fluorescence revele que l'intensite d'emission caracteristique d'europium augmente considerablement en presence de particules de ZnSe. Ce phenomene peut s'expliquer comme dfl au transfert d'energie resultant de la recombinaison electron-trou dans le ZnSe vers l'ion terre rare. Nous etudions l'absorption optique non lineeaire a la longueur d'onde de 532 nm en utilisant une technique z-scan. L'eechantillon montre une absorption saturable reversible (RSA) que nous trouvons dependre du debit radiatif d'excitation. La RSA est due a une absorption accrue qui resulte de la dynamique electronique dans les nano cristallites. [Traduit par la Redaction], 1. Introduction Rare earth ions possess optical transitions within the 4f level structure, which are crucial to the development of optical amplifiers and phosphor materials [1-3]. The radiative and nonradiative [...]