Search

We hereby propose the use of stable, biocompatible, and uniformly sized polymeric micelles as high-radiotracer-payload carriers at region-of-interest with negligible background activity due to no or low offsite radiolysis. We modified glycol chitosan (GC) polymer with varying levels of palmitoylation (P) and quaternization (Q). Quaternary ammonium palmitoyl glycol chitosan (GCPQ) with a Q:P ratio of 9:35 (Q9P35GC) offers >99% biocompatibility at 10 mg mL−1. Q9P35GC micelles exhibit >99% 99mTechnetium (99mTc) radiolabeling via the stannous chloride reduction method without heat. The 99mTc-Q9P35GC micelles (65 ± 3 nm) exhibit >98% 6 h serum stability at 37 °C and 7 day of radiochemical stability at 25 °C. HepG2 cells show a higher uptake of FITC-Q9P35GC than Q13P15GC and Q20P15GC. The in vivo 24 h organ cumulated activity (MBq h) order follows: liver (234.4) > kidneys (60.95) > GIT (0.73) > spleen (88.84). The liver to organ ratio remains higher than 2.4, rendering a better contrast in the liver. The radiotracer uptake decreases significantly in fibrotic vs. normal liver, whereas a blocking study with excess Q9P35GC significantly decreases the radiotracer uptake in a healthy vs. fibrotic liver. FITC-Q9P35GC shows in vivo hepato-specific uptake. Radiotracer liver uptake profile follows reversible binding kinetics with data fitting to two-tissue compartmental (2T), and graphical Ichise multilinear analysis (MA2) with lower AIC and higher R2 values, respectively. The study concludes that 99mTc-Q9P35GC can be a robust radiotracer for noninvasive hepatocyte function assessment and diagnosis of liver fibrosis. Furthermore, its multifunctional properties enable it to be a promising platform for nanotheranostic applications. [ABSTRACT FROM AUTHOR]

A microfluidic approach is described for generating capsules of biopolymer hydrogels at room temperature and with good control of particle size distribution and internal structure. The time of gelation and/or the concentration of the cross-linking agent in the continuous phase are controlled in order to achieve control over the internal structure of biomicrogels from capsules to gradient microgels to microgels with a uniform structure.

Localized surface plasmon polaritons (SSPs) have been observed on very small aperture lasers using apertureless near-field microscopy. Fields around multiple apertures are shown to result from interferences of SPP point sources at each aperture and optical fields. The near-field optical pattern around a single aperture indicates the interference of SPPs with their scattered counterparts. Near-field measurements also confirmed a preferred orientation of the rectangular aperture waveguide for the signal localization in very small aperture lasers. OCIS codes: 140.2020, 180.5810, 240.6680.

A method to measure charge within a molecular circuit that shows negative differential resistance by conducting probe atomic force microscopy is presented. It is observed that the voltage region over which conduction was enhanced correlated strongly with the region over which the scanning probe tip experienced capacitive attraction to the surface.

A study was conducted to report the coupling of vibrational excitations to photo induced electron transfer in a mixed-valence transition metal complex [(CN)(sub 5)OsCNRu(NH(sub 3))(sub 5)](super -). The studies observed excitations in the non-totally symmetric vibrational mode accompanying the reverse electron transfer process in both formamide (FA) and deuterium oxide (D(sub 2)O) solutions.

A semi classical theory of vibrational energy relaxation (VER) was studied which was extended to the case of molecular liquids and was used for calculating the VER rate constant in neat liquid oxygen at 77 K. The studies stated that VER in liquid oxygen was dominated by a purely quantum mechanical term which vanishes at the classical limit.

The first application of semiclassical methodology to the calculation of vibrational energy relaxation (VER) rate constants in condensed phase systems is presented. The studies stated that VER of high-frequency molecular vibrations was dominated by a purely quantum-mechanical term which vanishes in the classical limit.

The studies stated the dynamics of photochemical reactions exhibiting chemically which induced electron spin polarization (CIDEP) were modeled by kinetic equations that included all relevant parameters, including reaction of excited precursor as both a singlet and a triplet and spin exchange during radical encounters.

Quasielastic helium atom scattering (QHAS) techniques are used to study the diffusion and lateral vibrations of a low coverage Theta(sub Na)=0.043 of sodium atoms on a Pt(111) surface. On account of the competition between on-top and hollow site adsorption on the hexagonal Pt(111) surface, this system provides a comparison with the diffusion of Na/Cu(001).

The barrier to internal rotation of a methyl group attached to an unsaturated linkage in an organic molecule is changed by complex formation with a weakly bound argon atom. This is a result of a dispersion interaction between the argon and pie-electrons of the molecule in the vicinity of the methyl group.

A variable temperature scanning tunneling microscope was used to characterize interactions between diffusing hydrogen sulfide and water molecules and various coadsorbates on Cu(001). A single hydrogen atom abstraction in simple bimolecular reactions was induced and observed with atomic resolution.

The electronic excited-state at the air/water solvation dynamics of coumarin 314 adsorbed at the air/water interface was investigated Using femtosecond time-resolved second-harmonic generation (TRSHG). With the aid of a tunable optical parametric generator giving a spectral peak at 419+/- 3nm, the second-harmonic spectra of C314 was determined at air/water interface.

Potential pulse perturbation time-resolved scanning tunneling microscopy is used to investigate the growth and dissolution dynamics of nanoscale islands. It is concluded that the properties of the islands can be controlled by tailoring the potential pulse perturbation.

Gold and silicon nanostructures are produced by condensing vacuum-evaporated materials onto nanometer-sized etch-pit templates performed on the surface of highly oriented pyrolytic graphite. Scanning tunneling spectroscopy is used to further investigate the electronic properties of multilayered silicon nanostructures.

Atomic Force Microscopy has great scope to analyze contour lengths of polymers/macromolecules at surfaces. The values of persistence, lengths and other parameters obtained from filling the force-distance profiles indicate that the measurements typically involved stretching single PDMS molecules grafted to the underlying surfaces.

The impact of the polymer-solvent interfacial free energy on the collapse of the polystyrene chain in water, as well as the aqueous solutions is determined. The change in the free energy is shown to be directly related to the force of the collapsed polymer in a bad solvent.

The article describes the force-induced mechanics of individual polystyrene (PS130000) in strongly poor, moderately poor, and good solvent conditions.

Single-molecule electrical conduction studies are used to evaluate the way molecular linking unit influences the tunneling efficiency in metal-molecule-metal junctions. The results demonstrate that the molecule with conjugated double thiol linkers displays higher conduction in gold-molecule-gold junctions than non-conjugated single thiol-gold contacts.

An experimental data to characterize the diblock copolymer interactions with a silicon nitride AFM tip is described. The surface unbinding of individual polymer blocks under conditions where a specific solvent-polymer-surface structure is expected, is also described.

Transient pump–probe measurements have been made on betaine-30, the solvent polarity probe. Betaine-30 is composed of organic donor and acceptor groups, D+A-⇄kethνDA (excited state). The transient data has been analyzed to measure ket, the electron transfer (et) rate constant, in polar solvents for this inverted regime et. The observed rate constant ket,obs in various polar solvents is as much as a factor of 108 larger than is predicted by the standard, classical, implementation of the theory of Sumi and Marcus, using Kjaer and Ulstrup’s estimates for necessary parameters. In contrast, a quantum treatment of the vibrational modes by Jortner and Bixon, which includes the dynamic solvent effect, predicts that the rate should be approximately ket,JB[bar_over_tilde:_approx._equal_to]1/〈τs>. This is close to the experimental results ([bar_over_tilde:_approx._equal_to]1012 s-1) in typical polar aprotic solvents. However, in highly viscous, slowly relaxing solvents, ket,JB≪ket,obs. This is taken as evidence that the efficient coupling modes for the et in these environments is not the ‘‘conventional solvent coordinate.’’ It is shown that a hybrid of the Jortner/Bixon and Sumi/Marcus theories can physically account for the results. The kinetic behavior of betaine-30 in slowly relaxing solvents is shown to be in the ‘‘diffusionless limit’’ of the hybrid, generalized Sumi–Marcus/Jortner–Bixon picture. [ABSTRACT FROM AUTHOR]

The inverted regime photoinduced electron transfer kinetics of betaine-30 have been investigated over a broad temperature range, revealing very little temperature dependence. For example, for betaine-30 in a polystyrene film, the electron transfer rate constant, kET, changes by less than a factor of 3 from T=293 K to T=34 K. The results are in striking contrast to predictions of contemporary electron transfer theories which employ classical nuclear modes to accept some or all of the energy of the electron transfer event. The comparison of theory and experiment for the betaines demonstrates that a full quantum mechanical theory is necessary to accurately describe the electron transfer kinetics of the betaines in environments with slow dielectric relaxation. The conclusions drawn for the betaines may also apply to other molecular examples of inverted regime electron transfer in slowly relaxing environments. [ABSTRACT FROM AUTHOR]