Methylene blue protects astrocytes against glucose oxygen deprivation by improving cellular respiration.

Astrocytes outnumber neurons and serve many metabolic and trophic functions in the mammalian brain. Preserving astrocytes is critical for normal brain function as well as for protecting the brain against various insults. Our previous studies have indicated that methylene blue (MB) functions as an alternative electron carrier and enhances brain metabolism. In addition, MB has been shown to be protective against neurodegeneration and brain injury. In the current study, we investigated the protective role of MB in astrocytes. Cell viability assays showed that MB treatment significantly protected primary astrocytes from oxygen-glucose deprivation (OGD) & reoxygenation induced cell death. We also studied the effect of MB on cellular oxygen and glucose metabolism in primary astrocytes following OGD-reoxygenation injury. MB treatment significantly increased cellular oxygen consumption, glucose uptake and ATP production in primary astrocytes. In conclusion our study demonstrated that MB protects astrocytes against OGD-reoxygenation injury by improving astrocyte cellular respiration.

Preparation of plasmonic platforms of silver wires on gold mirrors and their application to surface enhanced fluorescence.

In this report we describe a preparation of silver wires (SWs) on gold mirrors and its application to surface enhanced fluorescence (SEF) using a new methodology. Silica protected gold mirrors were drop-coated with a solution of silver triangular nanoprisms. The triangular nanoprisms were slowly air-dried to get silver wires that self-assembled on the gold mirrors. Fluorescence enhancement was studied using methyl azadioxatriangulenium chloride (Me-ADOTA · Cl) dye in PVA spin-coated on a clean glass coverslip. New Plasmonic Platforms (PPs) were assembled by placing a mirror with SWs in contact with a glass coverslip spin-coated with a uniform Me-ADOTA · Cl film. It was shown that surface enhanced fluorescence is a real phenomenon, not just an enhancement of the fluorescence signal due to an accumulation of the fluorophore on rough nanostructure surfaces. The average fluorescence enhancement was found to be about 15-fold. The lifetime of Me-ADOTA · Cl dye was significantly reduced (∼ 4 times) in the presence of SWs. Moreover, fluorescence enhancement and lifetime did not show any dependence on the excitation light polarization.

Multiple-pulse pumping for enhanced fluorescence detection and molecular imaging in tissue.

Applications of fluorescence based imaging techniques for detection in cellular and tissue environments are severely limited by autofluorescence of endogenous components of cells, tissue, and the fixatives used in sample processing. To achieve sufficient signal-to-background ratio, a high concentration of the probe needs to be used which is not always feasible. Since typically autofluorescence is in the nanosecond range, long-lived fluorescence probes in combination with time-gated detection can be used for suppression of unwanted autofluorescence. Unfortunately, this requires the sacrifice of the large portion the probe signal in order to sufficiently filter the background. We report a simple and practical approach to achieve a many-fold increase in the intensity of a long-lived probe without increasing the background fluorescence. Using controllable, well separated bursts of closely spaced laser excitation pulses, we are able to highly increase the fluorescence signal of a long-lived marker over the endogenous fluorescent background and scattering, thereby greatly increasing detection sensitivity. Using a commercially available confocal microscopy system equipped with a laser diode and time correlated single photon counting (TCSPC) detection, we are able to enhance the signal of a long-lived Ruthenium (Ru)-based probe by nearly an order of magnitude. We used 80 MHz bursts of pulses (12.5 ns pulse separation) repeated with a 320 kHz repetition rate as needed to adequately image a dye with a 380 ns lifetime. Just using 10 pulses in the burst increases the Ru signal almost 10-fold without any increase in the background signal.

Generating multiple-pulse bursts for enhanced fluorescence detection.

The signal-to-background ratio is the limiting factor for fluorescence based detection, sensing, and imaging. A typical background signal will include direct scattering of excitation and Raman scattering of the sample as well as autofluorescence from the sample and additives. To improve the signal-to-background ratio, fluorophores of high brightness and/or high concentration of the fluorophores need to be used. Most of the background is instantaneous and short-lived (picosecond to nanosecond time scale), and using long-lived fluorescence probes combined with time-gated detection allows for significant suppression of unwanted background. Unfortunately, this approach requires substantial sacrifice of the probe signal in order to sufficiently filter the background unless the fluorescence lifetime of the probe is very long. However, long lived probes like ruthenium bipyridyl have relatively low brightness compared to probes that have shorter, 10-30 ns fluorescence lifetimes.We recently presented an approach based on bursts of multiple pulses that allowed for high probe signal amplification using long-lived ruthenium based probe (Ru) and an 80 MHz repetition-rate laser excitation. Unfortunately, Ru represents an extreme case for probe lifetime, and a probe with a shorter lifetime of 20 ns will require excitation from a pulsed source with much higher repetition rate to significantly enhance its signal. Such high repetition rates are not possible to generate with most of today's available electronics. In this report we present new approaches to optimize and generate bursts of pulses with high repetition rate within the burst and no need for new or improved electronics. The high repetition rates originate from a low-repetition source and are highly tunable. We demonstrate that a burst of 2-10 pulses spaced 3 ns apart (corresponding to a 'burst repetition rate' of 330 MHz) allows for high signal enhancement of the 20 ns probe over the sub-nanosecond/nanosecond background. Such an approach can be applied for any sensing format, allowing much higher sensitivity for detection. Since the energy of a single pulse is spread over a few pulses in the burst, the fluorophore's photostability also improves.

Elimination of autofluorescence in fluorescence correlation spectroscopy using the AzaDiOxaTriAngulenium (ADOTA) fluorophore in combination with time-correlated single-photon counting (TCSPC).

Fluorescence correlation spectroscopy (FCS) is a frequently applied technique that allows for the precise and sensitive analysis of molecular diffusion and interactions. However, the potential of FCS for in vitro or ex vivo studies has not been fully realized due in part to artifacts originating from autofluorescence (fluorescence of inherent components and fixative-induced fluorescence). Here, we propose the azadioxatriangulenium (ADOTA) dye as a solution to this problem. The lifetime of the ADOTA probe, about 19.4 ns, is much longer than most components of autofluorescence. Thus, it can be easily separated by time-correlated single-photon counting methods. Here, we demonstrate the suppression of autofluorescence in FCS using ADOTA-labeled hyaluronan macromolecules (HAs) with Rhodamine 123 added to simulate diffusing fluorescent background components. The emission spectrum and decay rate of Rhodamine 123 overlap with the usual sources of autofluorescence, and its diffusion behavior is well known. We show that the contributions from Rhodamine 123 can be eliminated by time gating or by fluorescence lifetime correlation spectroscopy (FLCS). While the pairing of ADOTA and time gating is an effective strategy for the removal of autofluorescence from fluorescence imaging, the loss of photons leads to erroneous concentration values with FCS. On the other hand, FLCS eliminates autofluorescence without such errors. We then show that both time gating and FLCS may be used successfully with ADOTA-labeled HA to detect the presence of hyaluronidase, the overexpression of which has been observed in many types of cancer.

Elimination of autofluorescence background from fluorescence tissue images by use of time-gated detection and the AzaDiOxaTriAngulenium (ADOTA) fluorophore.

Sample autofluorescence (fluorescence of inherent components of tissue and fixative-induced fluorescence) is a significant problem in direct imaging of molecular processes in biological samples. A large variety of naturally occurring fluorescent components in tissue results in broad emission that overlaps the emission of typical fluorescent dyes used for tissue labeling. In addition, autofluorescence is characterized by complex fluorescence intensity decay composed of multiple components whose lifetimes range from sub-nanoseconds to a few nanoseconds. For these reasons, the real fluorescence signal of the probe is difficult to separate from the unwanted autofluorescence. Here we present a method for reducing the autofluorescence problem by utilizing an azadioxatriangulenium (ADOTA) dye with a fluorescence lifetime of approximately 15 ns, much longer than those of most of the components of autofluorescence. A probe with such a long lifetime enables us to use time-gated intensity imaging to separate the signal of the targeting dye from the autofluorescence. We have shown experimentally that by discarding photons detected within the first 20 ns of the excitation pulse, the signal-to-background ratio is improved fivefold. This time-gating eliminates over 96 % of autofluorescence. Analysis using a variable time-gate may enable quantitative determination of the bound probe without the contributions from the background.

Detection of hyaluronidase activity using fluorescein labeled hyaluronic acid and Fluorescence Correlation Spectroscopy.

The over-expression of hyaluronidase has been observed in many types of cancer, suggesting that it may have utility for diagnosis. Here we present a technique for the detection of hyaluronidase using Fluorescence Correlation Spectroscopy (FCS). Hyaluronan macromolecules (HAs) have been heavily labeled with fluorescein amine resulting in strong self-quenching. In the presence of hyaluronidase, HA is cleaved into smaller, fluorescein-labeled fragments and the self-quenching is released. Such cleavage is manifested by the increased average diffusion rate of the HA fragments, increased concentration of individual, fluorescent HA fragments, and increased intensity. All three of these properties are monitored simultaneously throughout FCS measurements, both as a function of time and hyaluronidase concentration. The method we present provides a sensitive measure of hyaluronidase activity and requires extremely small amounts of the HA substrate.

Infectious scleritis after retinal surgery.

PURPOSE: To report a series of patients in whom infectious scleritis developed after vitreoretinal surgery. DESIGN: Interventional case series of four patients. METHODS: Medical records of patients at a single institution in whom infectious scleritis developed after vitreoretinal surgery were reviewed. RESULTS: In three patients, infectious scleritis developed after 20-gauge pars plana vitrectomy, and in one patient, infectious scleritis developed after a scleral buckling procedure. Three cases were had positive culture results; the identified organisms were Pseudomonas aeruginosa in two cases and methicillin-resistant Staphylococcus aureus in one. The fourth patient did not have culture results but responded rapidly to empiric treatment with moxifloxacin. In one patient, surgically induced necrotizing scleritis subsequently developed. CONCLUSIONS: Although infectious scleritis is an uncommon complication after vitreoretinal surgery, it should be a considered cause in patients with persistent postoperative pain and inflammation.

Ranibizumab: Phase III clinical trial results.

Ranibizumab therapy is the first treatment for neovascular AMD to improve vision for most patients. The benefits apply to all angiographic subtypes of neovascular AMD and across all lesion sizes. Although the pivotal phase III trials (MARINA and ANCHOR) used monthly injections of ranibizumab for 2 years, the ongoing PIER, PrONTO, and SAILOR trials are investigating less frequent dosing regimens, and preliminary results from the PrONTO study suggest that fewer injections will most likely result in visual acuity improvements similar to the results from the phase III trials. When comparing the ANCHOR results with the FOCUS results, it also becomes apparent that the combination of ranibizumab with PDT does not necessarily result in better visual acuity outcomes, and the use of PDT may even reduce the visual acuity benefits achieved with ranibizumab alone (see Figs. 1-3). It seems unlikely that combination therapy provides any significant advantage over ranibizumab alone unless the combination of PDT and ranibizumab can decrease the need for frequent retreatment. The results from the PrONTO Study already suggest that less frequent treatment with ranibizumab is possible by using a variable dosing regimen with OCT. Ranibizumab also seems to be safe, with the 2-year MARINA data showing no increase in the incidence of systemic adverse events that could be associated with anti-VEGF therapy, such as myocardial infarction and stroke. There was a hint of a safety concern, however, in the pooled 1-year safety results from the MARINA and ANCHOR trials. Although the combined rate of myocardial infarction and stroke during the first year of the ANCHOR and MARINA trials was similar in the control and the 0.3-mg ranibizumab arms (1.3% and 1.6% respectively), these adverse events were slightly higher in the 0.5-mg ranibizumab arm (2.9%). These differences are not statistically significant, however, and probably do not represent a dose-dependent increase in risk because the 2-year results from the MARINA trial with the same monthly injection regimen showed no increased risk of thromboembolic events. In December 2005, Genentech submitted a Biologics License Application to the FDA for the use of ranibizumab in the treatment of neovascular wet AMD based on 1-year clinical efficacy and safety data from the two pivotal phase III trials, ANCHOR and MARINA, and the phase I-II FOCUS trial. Genentech has been granted a 6-month Priority Review from the FDA with a decision anticipated 6 months from the December submission date or by the end of June 2006 [29]. By the summer of 2006, this revolutionary therapy should be available for the treatment of neovascular AMD. At that time, the major dilemma facing most retina specialists will be whether to use intravitreal ranibizumab or intravitreal bevacizumab, the low cost alternative, for the treatment of neovascular AMD.

Short-term safety and efficacy of intravitreal bevacizumab (Avastin) for neovascular age-related macular degeneration.

PURPOSE: To evaluate the safety and efficacy of intravitreal bevacizumab (Avastin, Genentech Inc.) for the treatment of neovascular age-related macular degeneration (ARMD). METHODS: A retrospective review was performed on consented patients with neovascular ARMD receiving intravitreal bevacizumab therapy. All patients received intravitreal bevacizumab at baseline with additional monthly injections given at the discretion of the treating physician. At each visit, a routine Snellen visual acuity assessment was performed followed by an ophthalmic examination and optical coherence tomography (OCT) imaging. RESULTS: Fifty-three eyes of 50 patients received an intravitreal bevacizumab injection between May and August 2005. Including the month 3 visit, the average number of injections was 2.3 out of a maximum of 4 injections. No serious drug-related ocular or systemic adverse events were identified. Improvements in visual acuity and central retinal thickness measurements were evident by week 1 and continued through month 3. At month 3, the mean visual acuity improved from 20/160 to 20/125 (P < 0.001) and the mean central retinal thickness decreased by 99.6 microm (P < 0.001). CONCLUSION: Off-label intravitreal bevacizumab therapy for neovascular ARMD was well tolerated over 3 months with improvements in visual acuity and OCT central retinal thickness measurements. While the long-term safety and efficacy of intravitreal bevacizumab remain unknown, these short-term results suggest that intravitreal bevacizumab may be the most cost effective therapy for the treatment of neovascular ARMD.

Use of autologous platelet concentrate in blepharoplasty surgery.

PURPOSE: To evaluate postoperative edema and ecchymosis after blepharoplasty surgery with or without autologous platelet gel. METHODS: In this prospective, randomized, controlled trial, patients received autologous platelet concentrate in the eyelid incisions of one side during bilateral blepharoplasty surgery. The opposing eye was not treated and was used as a control. Autologous platelet concentrate was prepared by the Harvest system (Harvest Technologies, Plymouth, MA, U.S.A.). The blood was centrifuged and platelet-rich plasma isolated. Platelet-rich plasma was mixed with thrombin and instilled in the wound on a randomly selected side before wound closure. Patients were examined and completed a questionnaire at postoperative days 1, 3, 7, and 30. Photographs were taken at each visit and were graded by masked, trained observers for edema and ecchymosis. RESULTS: Significantly less edema (p<0.05) was noted by the photograders at day 1 and by the patients at day 30. There were non-statistically significant trends toward decreased ecchymosis and edema in the treated group. Questionnaire data showed no significant difference in postoperative pain between the treated and untreated sides. Photographic and questionnaire data showed no clinically meaningful difference between the treated and control sides. CONCLUSIONS: Although there were statistically significant differences in edema using autologous platelet gel in blepharoplasty surgery, trends toward improvement in postoperative edema and ecchymosis did not achieve clinical significance.