Investigating the interactions of corona-free SWCNTs and cell membrane models using sum-frequency generation.

The understanding of the interactions between biomolecules and nanomaterials is of great importance in many areas of nanomedicine and bioapplications. Numerous studies in this area have been performed. However, toxicological aspects involving the interaction between phospholipids and carbon nanotubes (CNTs) remain undefined, especially for those cases in which a protein corona is not formed around the nanomaterial (corona-free nanomaterials). This study focuses on the interaction of Langmuir films of dipalmitoylphosphatidylglycerol (DPPG) and dipalmitoylphosphatidylcholine (DPPC) with corona-free, single-walled CNTs. Surface pressure-area isotherms and sum-frequency generation (SFG) vibrational spectroscopy, a non-linear optical technique used to study surfaces and interfaces, were used to investigate the lipid tail orientation and conformation, aiming to understand the interactions between phospholipids and single walled carbon nanotubes functionalized by carboxylic acid (SWCNTs-COOH) at the air-water interface under low ionic strength conditions. Data from isotherms and SFG spectra revealed that the SWCNT adsorption at the air-water interface is induced by the presence of both lipids, although at a lesser extent for DPPG due to its anionic head group, which could result in repulsion of SWCNTs-COOH that also bear a negative charge. Furthermore, lipid monolayers remained conformationally ordered, indicating insertion of SWCNTs into the lipid monolayer. Our results corroborate previous works and simulations in the literature, but made it possible to perform an in-depth investigation of the interaction of these nanomaterials with components of phospholipid membranes.

The Photophysics of Polythiophene Nanoparticles for Biological Applications.

In this work the photophysics of poly(3-hexylthiophene) nanoparticles (NPs) is investigated in the context of their biological applications. The NPs, made as colloidal suspensions in aqueous buffers, present a distinct absorption band in the low-energy region. On the basis of systematic analysis of absorption and transient absorption (TA) spectra taken under different pH conditions, this band is associated with charge-transfer states generated by the polarization of loosely bound polymer chains and originating from complexes formed with electron-withdrawing species. Importantly, the ground-state depletion of these states upon photoexcitation is active even on microsecond timescales, thus suggesting that they act as precursor states for long-living polarons; this could be beneficial for cellular stimulation. Preliminary transient absorption microscopy results for NPs internalized within the cells reveal the presence of long-living species, further substantiating their relevance in biointerfaces.

A detailed investigation on the interactions between magnetic nanoparticles and cell membrane models.

The understanding of the interactions between small molecules and magnetic nanoparticles is of great importance for many areas of bioapplications. Although a large array of studies in this area have been performed, aspects involving the interaction of magnetic nanoparticles with phospholipids monolayers, which can better mimic biological membranes, have not yet been clarified. This study was aimed at investigating the interactions between Langmuir films of dipalmitoyl phosphatidylglycerol and dipalmitoyl phosphatidylcholine, obtained on an aqueous subphase, and magnetic nanoparticles. Sum-frequency generation (SFG) vibrational spectroscopy was used to verify the orientation and molecular conformation and to better understand the interactions between phospholipids and the magnetic nanoparticles. Surface pressure-area isotherms and SFG spectroscopy made it possible to investigate the interaction of these nanomaterials with components of phospholipids membranes at the water surface.