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Molecular imaging techniques are essential tools for better investigating biological processes and detecting disease biomarkers with improvement of both diagnosis and therapy monitoring. Often, a single imaging technique is not sufficient to obtain comprehensive information at different levels. Multimodal diagnostic probes are key tools to enable imaging across multiple scales. The direct registration of in vivo imaging markers with ex vivo imaging at the cellular level with a single probe is still challenging. Fluorinated (19F) probes have been increasingly showing promising potentialities for in vivo cell tracking by 19F-MRI. Here we present the unique features of a bioorthogonal 19F-probe that enables direct signal correlation of MRI with Raman imaging. In particular, we reveal the ability of PERFECTA, a superfluorinated molecule, to exhibit a remarkable intense Raman signal distinct from cell and tissue fingerprints. Therefore, PERFECTA combines in a single molecule excellent characteristics for both macroscopic in vivo 19F-MRI, across the whole body, and microscopic imaging at tissue and cellular levels by Raman imaging.

(19)F-MRI offers unique opportunities to image diseases and track cells and therapeutic agents in vivo. Herein we report a superfluorinated molecular probe, herein called PERFECTA, possessing excellent cellular compatibility, and whose spectral properties, relaxation times, and sensitivity are promising for in vivo (19)F-MRI applications. The molecule, which bears 36 equivalent (19)F atoms and shows a single intense resonance peak, is easily synthesized via a simple one-step reaction and is formulated in water with high stability using trivial reagents and methods.

Sum frequency generation (SFG) imaging is used to monitor, in situ, the reaction of cyanide ions with gold surface. Spatial and chemical variations across the surface are observed as a function of time. The initial period resulted in the formation of linearly bound cyanide to gold, and continuous exposure of gold film to cyanide solution led to the presence of higher-coordinated gold-cyanide complexes. These species were identified by their specific position in the SFG vibrational spectrum (2105, 2140, 2170, and 2225 cm(-1)). The relative amounts of these gold-cyanide species varied across the surface as resolved by SFG microscopy.

We report the successful application of SFG to detect segregation of end groups on polymer surfaces. Two groups of polymer samples are studied: one is polyurethane with different surface-modified end groups, the other is poly(ethylene glycol) (PEG) with different end groups. For each group of polymers, both hydrophobic and hydrophilic end groups are chosen. With the surface sensitivity of SFG, we have found that hydrophobic end groups [e.g., methoxy on PEG or poly(dimethylsiloxane) (PDMS) on polyurethane] tend to segregate to the polymer surface in air. However, the hydrophilic end groups (e.g., hydroxyl group on PEG or PEG on polyurethane) remain in the bulk so that the surfaces that are exposed to air are covered by the polymer backbones. Although contact-angle measurements and XPS results can demonstrate that polymer surfaces indeed have been modified by different end groups, only SFG can show the surface structure at the molecular level.

Vibrational spectroscopy, sum frequency generation, has been used to study the gas−liquid interface of imidazolium-based, room-temperature ionic liquids. The ionic liquids are divided into two categories on the basis of their miscibility with water, as hydrophobic (immiscible) and hydrophilic (miscible). The spectroscopy results indicate that water will reorient the cations of the hydrophobic ionic liquid, while in the hydrophilic ones they remain unaffected. Thus, under low water conditions the plane of the imidazolium ring remains parallel to the surface for both types of ionic liquid. However, at high water content the ring will reorient to along the surface normal for the hydrophobic ionic liquid but remain parallel to the surface for the hydrophilic one. This is a reversible process.

Sum frequency generation (SFG) vibrational spectra of D(2)O and/or acetonitrile (CH(3)CN) on a Pt(111) single-crystal electrode were obtained as a function of applied potential in a 5 mol % water/acetonitrile mixed solvent with different 0.1 molar MSO(3)CF(3) salts (M = H(+), Li(+), Na(+), K(+), and Cs(+)). The results provide a very specific model for the composition of the inner Helmholtz layer as a function of potential and surface charge. Acetonitrile dominates the inner layer with the CN group directed toward the metal at potentials where the metal has a positive charge. As the surface becomes negatively charged, the acetonitrile orientation flips 180 degrees, with the CH(3) group pointing toward the surface. At even more negative surface charge, D(2)O displaces acetonitrile from the inner layer and is the predominant molecule on the surface. Here water is present as an oriented molecule with the oxygen end pointing toward the metal. The potential (and surface charge) where water is the dominant molecule in the inner Helmholtz layer is determined by the solvation energy of the cation.

Most of the current research on synthetic bilayer membrane-nucleic acid complexes (lipoplexes) is addressed to lipid self-assemblies as nonviral vectors for genetic material. The vast majority of synthetic nonviral vectors so far considered consists of cationic lipid assemblies where DNA binds to cationic liposomes, thanks to charge compensation between the negative polyelectrolyte and the headgroups of the cationic lipid assembly. We report a SAXS investigation with the first evidence of formation of an ordered lamellar phase of the type Lαc without any mediation from divalent cations or the presence of cationic lipids, where the complementary polynucleotide strands spontaneously order in between a lamellar fluid phase formed by the anionic 1-palmitoyl-2-oleoyl-phosphatidyl-adenosine nucleolipid, POPA. This nucleolipid has full biological compatibility and can be enzymatically cleaved by phospholipases once in living organisms. While for conventional lipoplexes the driving force leading to condensation i...

Sum frequency vibrational spectroscopy is utilized as an imaging technique to distinguish and compare the local response of carbon monoxide (CO) covered platinum (Pt) polycrystalline surface versus the average response of the investigated area. The Pt electrode was prepared using the standard method and was exposed to approximately 1 atm of CO(g). SFG images and vibrational spectra were obtained where the contrast is based on the intrinsic nature of each peak in the CO vibrational spectrum. The illustration of the images and the chemical maps of CO on the platinum surface showed the distribution of the CO across the observed area. The results obtained by comparing the local and the average response confirmed the spatial distributions of the CO on the platinum sample which are due to several reasons such as dipole-dipole coupling and surface coverage. This finding has a significant contribution toward recognizing that surfaces usually considered homogeneous may in fact be quite heterogeneous.