Qiushi Ren

Mesoporous silica-coated gold nanorods with embedded indocyanine green for dual mode X-ray CT and NIR fluorescence imaging

Indocyanine green-loaded mesoporous silica-coated gold nanorods (ICG-loaded Au@SiO2) were prepared for the dual capability of X-ray computed tomography (CT) and fluorescence imaging. X-ray CT scanning showed that ICG-loaded Au@SiO2 could provide significant contrast enhancement; Near-infrared fluorescence generated by the nanomaterial was present up to 12 h post intratumoral injection, thus enabling ICG-loaded Au@SiO2 to be used as a promising dual mode imaging contrast agent. Multiplexed images can be more easily obtained with this novel type of multimodal nanostructure compared with traditional contrast agents. The dual mode imaging probe has great potential for use in applications such as cancer targeting, molecular imaging in combination with radiotherapy, and photothermolysis.

RGD-conjugated gold nanorods induce radiosensitization in melanoma cancer cells by downregulating αvβ3 expression

Background Melanoma is known to be radioresistant and traditional treatments have been intractable. Therefore, novel approaches are required to improve the therapeutic efficacy of melanoma treatment. In our study, gold nanorods conjugated with Arg-Gly-Asp peptides (RGD-GNRs) were used as a sensitizer to enhance the response of melanoma cells to 6 mV radiation. Methods and materials A375 melanoma cells were treated by gold nanorods or RGD-GNRs with or without irradiation. The antiproliferative impact of the treatments was measured by MTT assay. Radiosensitizing effects were determined by colony formation assay. Apoptosis and cell cycle data were measured by flow cytometry. Integrin αvβ3 expression was also investigated by flow cytometry. Results Addition of RGD-GNRs enhanced the radiosensitivity of A375 cells with a dose-modifying factor of 1.35, and enhanced radiation-induced apoptosis. DNA flow cytometric analysis indicated that RGD-GNRs plus irradiation induced significant G2/M phase arrest in A375 cells. Both spontaneous and radiation-induced expressions of integrin αvβ3 were downregulated by RGD-GNRs. Conclusion Our study indicated that RGD-GNRs could sensitize melanoma A375 cells to irradiation. It was hypothesized that this was mainly through downregulation of radiation-induced αvβ3, in addition to induction of a higher proportion of cells within the G2/M phase. The combination of RGD-GNRs and radiation needs further investigation.

Graphene/Intermetallic PtPb Nanoplates Composites for Boosting Electrochemical Detection of H2O2 Released from Cells

Rational design and construction of electrocatalytic nanomaterials is vital for improving the sensitivity and selectivity of nonenzymatic electrochemical sensors. Here, we report a novel graphene supported intermetallic PtPb nanoplates (PtPb/G) nanocomposite as an enhanced electrochemical sensing platform for high-sensitivity detection of H2O2 in neutral solution and also released from the cells. The intermetallic PtPb nanoplates are first synthesized via a simple wet-chemistry process and subsequently assembled on graphene via a solution-phase self-assembly approach. The obtained nanocomposite exhibits excellent electrocatalytic activity for the electrochemical reduction of H2O2 in a half-cell test and can detect H2O2 with a wide linear detection range of 2 nM to 2.5 mM and a very low detection limit of 2 nM. Under the same conditions, the sensitivity of PtPb/G for the detection of H2O2 is more than 12.7 times higher than that of commercial Pt/C. The high-density of electrocatalytic active sites on the unique PtPb nanoplates and the synergistic effect between PtPb nanoplates and graphene appear to be the main factors in contributing to the outstanding electroanalytical performance. The PtPb/G can be also used for the practical detection of H2O2 released from Raw 264.7 cells.

Optical coherence tomography for whole eye segment imaging

We proposed a dual focus dual channel spectral domain optical coherence tomography (SD-OCT) for simultaneous imaging of the whole eye segments from cornea to the retina. By using dual channels the system solved the problem of limited imaging depth of SD-OCT. By using dual focus the system solved the problem of simultaneous light focusing on the anterior segment of the eye and the retina. Dual focusing was achieved by adjusting the collimating lenses so the divergence of the two probing beams was tuned to make them focused at different depth in the eye. We further achieved full range complex (FRC) SD-OCT in one channel to increase the depth range for anterior segment imaging. The system was successfully tested by imaging a human eye in vivo.

Achieving λ/10 resolution CW STED nanoscopy with a Ti:Sapphire oscillator.

In this report, a Ti:Sapphire oscillator was utilized to realize synchronization-free stimulated emission depletion (STED) microscopy. With pump power of 4.6 W and sample irradiance of 310 mW, we achieved super-resolution as high as 71 nm. With synchronization-free STED, we imaged 200 nm nanospheres as well as all three cytoskeletal elements (microtubules, intermediate filaments, and actin filaments), clearly demonstrating the resolving power of synchronization-free STED over conventional diffraction limited imaging. It also allowed us to discover that, Dylight 650, exhibits improved performance over ATTO647N, a fluorophore frequently used in STED. Furthermore, we applied synchronization-free STED to image fluorescently-labeled intracellular viral RNA granules, which otherwise cannot be differentiated by confocal microscopy. Thanks to the widely available Ti:Sapphire oscillators in multiphoton imaging system, this work suggests easier access to setup super-resolution microscope via the synchronization-free STED.

Mirror-enhanced super-resolution microscopy

Axial excitation confinement beyond the diffraction limit is crucial to the development of next-generation, super-resolution microscopy. STimulated Emission Depletion (STED) nanoscopy offers lateral super-resolution using a donut-beam depletion, but its axial resolution is still over 500 nm. Total internal reflection fluorescence microscopy is widely used for single-molecule localization, but its ability to detect molecules is limited to within the evanescent field of ~100 nm from the cell attachment surface. We find here that the axial thickness of the point spread function (PSF) during confocal excitation can be easily improved to 110 nm by replacing the microscopy slide with a mirror. The interference of the local electromagnetic field confined the confocal PSF to a 110-nm spot axially, which enables axial super-resolution with all laser-scanning microscopes. Axial sectioning can be obtained with wavelength modulation or by controlling the spacer between the mirror and the specimen. With no additional complexity, the mirror-assisted excitation confinement enhanced the axial resolution six-fold and the lateral resolution two-fold for STED, which together achieved 19-nm resolution to resolve the inner rim of a nuclear pore complex and to discriminate the contents of 120 nm viral filaments. The ability to increase the lateral resolution and decrease the thickness of an axial section using mirror-enhanced STED without increasing the laser power is of great importance for imaging biological specimens, which cannot tolerate high laser power.

Spatiotemporal Properties of Multipeaked Electrically Evoked Potentials Elicited by Penetrative Optic Nerve Stimulation in Rabbits

PURPOSE To investigate the spatiotemporal properties of the cortical responses elicited by intraorbital optic nerve (ON) stimulation with penetrating electrodes as means of designing optimal stimulation strategies for an ON visual prosthesis. METHODS The ON of rabbits was exposed by orbital surgery for electrical stimulation. Craniotomy was performed to expose the visual cortex contralateral to the operated eye. Electrically evoked potentials (EEPs) were recorded by an electrode array positioned on the visual cortex. RESULTS There were primarily four components (N1, P1, P2, P3) in EEPs with implicit times of 8.0 ± 0.6, 11.3 ± 1.3, 20.5 ± 1.4, and 26.9 ± 1.5 ms, respectively, when the ON was stimulated by penetrating electrodes. The thresholds to elicit these components were different, and the higher thresholds were seen with slower cortical components. The corresponding thresholds were 13.8 ± 3.1 μA for N1, 21.8 ± 4.7 μA for P1, 36.4 ± 11.4 μA for P2, and 68.4 ± 17.2 μA for P3. The time courses of the EEP components were also distinct. The locations of EEPs with the maximum P1 amplitude showed a spatial correspondence to the ON stimulation sites. Different profiles of cortical responses could be discriminated when the ON stimulation sites were separated by 150 μm. CONCLUSIONS Multiple components with different properties were elicited in EEPs when the ON was stimulated by penetrating electrodes. Retinotopic and localized stimulation could be achieved with this stimulating approach.

Corneal nerve morphology and sensitivity changes after ultraviolet A/riboflavin treatment

Collagen crosslinking induced by riboflavin and ultraviolet A irradiation (UVAR) has recently been introduced as a clinical treatment to halt or reverse the progression of keratoconus. We investigated changes in corneal sensitivity and nerve morphology as part of a comprehensive safety evaluation of this treatment. Fifty-four New Zealand white rabbits were divided into three experimental groups: UVAR with deepithelialization, UVAR without deepithelialization, and deepithelialization alone. Corneal sensitivity was measured with a Cochet-Bonnet esthesiometer before treatment and 3, 7, 14, 30, 90, and 180 days after treatment. Corneal nerve morphology was evaluated using acetylcholinesterase histochemistry staining. We found that corneal sensitivity in the center of the treated area was significantly reduced 3 days after UVAR with deepithelialization treatment compared with the corneal sensitivity of the control eye but gradually recovered to normal levels at 90 days. Corneal sensitivity after deepithelialization treatment was significantly lower than control corneal sensitivity at 3 days but was significantly higher after 30 days of recovery compared with the corneal sensitivity after UVAR with deepithelialization. Corneal sensitivity after UVAR without deepithelialization treatment had significantly decreased at 7 days compared with control corneal sensitivity but was not significantly different from control values at other measurement times. In parallel with these functional alterations, corneal nerve degeneration was visible in the treatment area by 3 days; by 7 days there was a significant decrease in nerve density. Corneal nerve sprouts were identified from neighboring non-injured nerve fibers 7 days after treatment; by 90 days, excessively regenerating nerves were observed throughout the anterior stroma. The density of corneal nerve fibers appeared normal by 180 days. Ultraviolet A/riboflavin with deepithelialization treatment resulted in corneal nerve fiber damage and subsequent regeneration in the treatment area, simultaneously accompanied by the reduction and recovery of corneal sensitivity.

Electrical stimulation with a penetrating optic nerve electrode array elicits visuotopic cortical responses in cats

OBJECTIVE A visual prosthesis based on penetrating electrode stimulation within the optic nerve (ON) is a potential way to restore partial functional vision for blind patients. We investigated the retinotopic organization of ON stimulation and its spatial resolution. APPROACH A five-electrode array was inserted perpendicularly into the ON or a single electrode was advanced to different depths within the ON (~1-2 mm behind the eyeball, 13 cats). A sparse noise method was used to map ON electrode position and the visual cortex. Cortical responses were recorded by a 5 × 6 array. The visuotopic correspondence between the retinotopic position of the ON electrode was compared with the visual evoked cortical map and the electrical evoked potentials elicited in response to ON stimulation. MAIN RESULTS Electrical stimulation with penetrating ON electrodes elicited cortical responses in visuotopographically corresponding areas of the cortex. Stimulation of the temporal side of the ON elicited cortical responses corresponding to the central visual field. The visual field position shifted from the lower to central visual field as the electrode penetrated through the depth of the ON. A spatial resolution of ~ 2° to 3° within a limited cortical visuotopic representation could be obtained by this approach. SIGNIFICANCE Visuotopic electrical stimulation with a relatively fine spatial resolution can be accomplished using penetrating electrodes implanted at multiple sites and at different depths within the ON just behind the globe. This study also provides useful experimental data for the design of electrode density and the distribution of penetrating ON electrodes for a visual prosthesis.

Chinese Character Recognition Using Simulated Phosphene Maps

PURPOSE A visual prosthetic device may produce phosphene maps in which individual phosphene characteristics can be altered. This study was an investigation of the ability of normally sighted subjects to recognize Chinese characters (CCs) after altering simulated phosphene maps. METHODS Thirty volunteers with normal or corrected visual acuity of 20/20 were recruited. CC recognition accuracy and response time were investigated while one parameter was changed (distortion, pixel dropout percentage, pixel size variability, or pixel gray level) or different combinations of three parameters were used. Five hundred CCs consisting of 1 to 16 strokes were used for the character sets. RESULTS CC recognition accuracy and response times respectively decreased and increased when distortion, dropout, and pixel size variability increased. Gray levels did not significantly affect the results, except when eight levels were used. To maintain an 80% accuracy rate, there should be a distortion index (k) of no more than 0.2 (irregularity), a pixel dropout of 20%, and a pixel size range of 1 to 16 mm (7-112 min arc). Only a combination of a k=0.1 distortion index, a dropout of 10%, and a pixel size range of 1.33 to 12 mm (9.3-84 min arc) achieved a goal of ≥80% accuracy. CONCLUSIONS Distortion, dropout percentage, and pixel size variability have a significant impact on pixelated CC recognition. Although at present the visual ability of prosthesis users is limited, it should be possible to extend this to CC recognition and reading in the future. The results will help visual prosthesis researchers determine the effects of altering phosphene maps and improve outcomes for patients.