Eur. Phys. J. Special Topics 153, 357–360 (2008) c  EDP Sciences, Springer-Verlag 2008 DOI: 10.1140/epjst/e2008-00461-1 T HE EUROPEAN P HYSICAL JOURNAL SPECIAL TOPICS Photoacoustic investigation of maghemite-based BSA nanocomposite L.B. Silveira 1 , J.G. Santos 1 , A.C. Oliveira 2 , B.M. Lacava 2 , A.C. Tedesco 3 , and P.C. Morais 2 1 Funda¸ c˜ ao Universidade Federal de Rondˆ onia, Departamento de Ciˆ encias Exatas e da Natureza, Ji-Paran´a RO 78961-970, Brazil 2 Universidade de Bras´ ılia, Instituto de F´ ısica, N´ ucleo de F´ ısica Aplicada, Bras´ ılia DF 70910-900, Brazil 3 Departamento de Qu´ ımica, Laborat´ orio Fotobiologia e Fotomedicina Faculdade de Filosofia, Ciˆ encias e Letras de Ribeir˜ ao Preto, Universidade de S˜ao Paulo, 14040-901, Ribeir˜ ao Preto-SP, Brazil Abstract. Maghemite-based bovine serum albumin (BSA) nanocomposites have been investigated using photoacustic spectroscopy (PAS). Features in the PAS spectra were analyzed in terms of three bands (band-C, band-S, and band-L). Though the observed PAS peak positions are insensitive to the nanoparticle con- centration the PAS peak intensity displays a different behaviour. For band-C the PAS intensity scales almost linearly with the nanoparticle concentration in the hosting template. Nevertheless, it was found that the PAS intensity of band-L scales sub-linearly with the nanoparticle concentration. 1 Introduction Biocompatible nanocomposites have attracted intense interest in recent years, particularly due to the positive impact they offered to the biological and biomedical applications, ranging from the cell sorting technology to alternative cancer therapies [1–3]. More recently, huge effort has been done towards the design and synthesis of new drug delivery systems using biocompat- ible magnetic nanocomposites [4,5]. Different biocompatible templates can be used to host magnetic nanoparticles, with special emphasis on maghemite nanoparticles introduced in the hosting template using pre-synthesized magnetic fluid (MF) samples [6]. In addition to the magnetic nanoparticle the hosting template may carry a specific drug as well. As long as the end magnetic nanocomposite offers long term biocompatibility and chemical stability a wide range of applications opens up based on such material platform [4–8]. In the present study, bovine serum albumin-based (BSA-based) nanosized spheres were used as the biocompatible template to host different amounts of maghemite nanoparticles, thus producing a series of five biocompatible magnetic nanocomposite (BMNC) samples. The BMNC samples were investi- gated using photoacoustic spectroscopy (PAS) with the aim to help understand the interaction between the maghemite nanoparticle and the hosting template. Interpretation of the PAS data, in the optical excitation range of 0.3 to 1.0 μm, was carried out based on previous investigations considering three different bands named band-C, band-S, and band-L [9]. As complementary experimental techniques transmission electron microscopy (TEM) and X-ray diffraction (XRD) were employed for basic characterization of the MF sample used to incorporate maghemite nanoparticles in the hosting template.