Au nanostar nanoparticle as a bio-imaging agent and its detection and visualization in biosystems.

In the present work, we report the imaging of Au nanostars nanoparticles (AuNSt) and their multifunctional applications in biomedical research and theranostics applications. Their optical and spectroscopic properties are considered for the multimodal imaging purpose. The AuNSt are prepared by the seed-meditated method and characterized for use as an agent for bio-imaging. To demonstrate imaging with AuNSt, penetration and localization in different biological models such as cancer cell culture (A549 lung carcinoma cell), 3D tissue model (multicellular tumor spheroid on the base of human oral squamous carcinoma cell, SAS) and murine skin tissue are studied. AuNSt were visualized using fluorescence lifetime imaging (FLIM) at two-photon excitation with a pulse duration 140 fs, repetition rate 80 MHz and 780 nm wavelength femtosecond laser. Strong emission of AuNSt at two-photon excitation in the near infrared range and fluorescence lifetime less than 0.5 ns were observed. It allows using AuNSt as a fluorescent marker at two-photon fluorescence microscopy and lifetime imaging (FLIM). It was shown that AuNSt can be observed inside a thick sample (tissue and its model). This is the first demonstration using AuNSt as an imaging agent for FLIM at two-photon excitation in biosystems. Increased scattering of near-infrared light upon excitation of AuNSt surface plasmon oscillation was also observed and rendered using a possible contrast agent for optical coherence tomography (OCT). AuNSt detection in a biological system using FLIM is compared with OCT on the model of AuNSt penetrating into animal skin. The AuNSt application for multimodal imaging is discussed.

Towards enhanced optical sensor performance: SEIRA and SERS with plasmonic nanostars.

We report the preparation and characterization of plasmonic chip-based systems comprising self-assembled gold nanostars at silicon substrates that enable concomitantly enhanced Raman (surface enhanced Raman spectroscopy; SERS) and mid-infrared (surface enhanced infrared reflection or absorption spectroscopy; SEIRA) spectral signatures. The high-aspect-ratio structure of gold nanostars provides an increased number of hot spots at their surface, which results in an electric field enhancement around the nanomaterial. Gold nanostars were immobilized at a silicon substrate via a thin gold layer, and α-ω-dimercapto polyethylene glycol (SH-PEG-SH) linkers. The Raman and IR spectra of crystal violet (CV) revealed a noticeable enhancement of the analyte vibrational signal intensity in SERS and SEIRA studies resulting from the presence of the nanostars. Enhancement factors of 2.5 × 103 and 2.3 × 103 were calculated in SERS considering the CV bands at 1374.9 cm-1 and 1181 cm-1, respectively; for SEIRA, an enhancement factor of 5.36 was achieved considering the CV band at 1585 cm-1.

Challenges in nanoelectrochemical and nanomechanical studies of individual anisotropic gold nanoparticles.

The characterization of nanoparticles and the correlation of physical properties such as size and shape to their (electro)chemical properties is an emerging field, which may facilitate future optimization and tuning of devices involving nanoparticles. This requires the investigation of individual particles rather than obtaining averaged information on large ensembles. Here, we present atomic force - scanning electrochemical microscopy (AFM-SECM) measurements of soft conductive PDMS substrates modified with gold nanostars (i.e., multibranched Au nanoparticles) in peak force tapping mode, which next to the electrochemical characterization provides information on the adhesion, deformation properties, and Young's modulus of the sample. AFM-SECM probes with integrated nanodisc electrodes (radii < 50 nm) have been used for these measurements. Most studies attempting to map individual nanoparticles have to date been performed at spherical nanoparticles, rather than highly active asymmetric gold nanoparticles. Consequently, this study discusses challenges during the nanocharacterization of individual anisotropic gold nanostars.

Multiresolution analysis of pathological changes in cerebral venous dynamics in newborn mice with intracranial hemorrhage: adrenorelated vasorelaxation.

Intracranial hemorrhage (ICH) is the major problem of modern neonatal intensive care. Abnormalities of cerebral venous blood flow (CVBF) can play a crucial role in the development of ICH in infants. The mechanisms underlying these pathological processes remain unclear; however it has been established that the activation of the adrenorelated vasorelaxation can be an important reason. Aiming to reach a better understanding of how the adrenodependent relaxation of cerebral veins contributes to the development of ICH in newborns, we study here the effects of pharmacological stimulation of adrenorelated dilation of the sagittal sinus by isoproterenol on the cerebral venous hemodynamics. Our study is performed in newborn mice at different stages of ICH using the laser speckle contrast imaging and wavelet analysis of the vascular dynamics of CVBF. We show that the dilation of the sagittal sinus with the decreased velocity of blood flow presides to the stress-induced ICH in newborn mice. These morphofunctional vascular changes are accompanied by an increased variance of the wavelet-coefficients in the areas of endothelial and non-endothelial (KATP-channels activity of vascular muscle) sympathetic components of the CVBF variability. Changes in the cerebral venous hemodynamics at the latent stage of ICH are associated with a high responsiveness of the sagittal sinus to isoproterenol quantifying by wavelet-coefficients related to a very slow region of the frequency domain. The obtained results certify that a high activation of the adrenergic-related vasodilatory responses to severe stress in newborn mice can be one of the important mechanisms underlying the development of ICH. Thus, the venous insufficiency with the decreased blood outflow from the brain associated with changes in the endothelial and the sympathetic components of CVBF-variability can be treated as prognostic criteria for the risk of ICH during the first days after birth.

Mechanisms for vascular effects of androgens in normotensive and hypertensive rats.

Castration had no effect on baseline BP and vascular sensitivity to acetylcholine and deficiency of nitric oxide and prostacyclin in normotensive specimens. Castration of hypertensive specimens decreased BP and potentiated the hypotensive effects of acetylcholine, but did not modulate vascular sensitivity to the blockade of nitric oxide and prostacyclin synthesis. The removal of the testicles abolished the pressor influence of glybenclamide in hypertensive and, particularly, in normotensive males. These data indicate that the non-endothelial vascular effects of androgens (i.e., stimulation of K(ATP) channels) predominate under normal conditions. The activating effects of androgens on K(ATP) channels decrease during hypertension, which is accompanied by inhibition of endothelium-dependent vasorelaxation. The production of nitric oxide and prostacyclin remains unchanged under these conditions. Our results suggest that endothelium-derived hyperpolarizing factor is involved in these processes.

[Gene expression of the interferon and cell-immunity systems in human blood samples].

The interferon (IF) and cell-apoptosis (CA) systems are interrelated and regulate the protective reactions in body by means of a complex of biologically active proteins. The transcription levels of mRNA were determined by the RT-PCR semi-quantitative method in order to compare the constitutive expression levels of IF (alpha, beta, gamma) genes, IF-dependent enzymes of 2'5'-oligoadenylatesynthetyase (OAS), RNAase L, dsRNA-protein kinase (dsPK) and CA effectors (Fas-Ag, bcl-2 and gamma-actin) in human blood microsamples. cDNA dilutions, different numbers of amplification cycles (PCR with specific pairs of primers) as well as PCR-products' dilutions for dot-hybridization with specific probes were made use of to detect and evaluate levels of 9 mRNAs. The constitutive levels of gene expression of the IF and CA systems were found to differ essentially from others (1000-fold). The studied mRNA types were shared between 5 groups according to their transcription levels: very high--alpha-IF, high--RNAase L, medium--gamma-actin and bcl-2, low--beta-IF and very low (detectable after induction only)--gamma-IF, OAS, dsPK and Fas-Ag. The used detection method has a sufficiently high sensitivity and can be recommended for studies of IF inductors with unknown action mechanisms.