Au-Ag Alloy Nanoshuttle Mediated Surface Plasmon Coupling for Enhanced Fluorescence Imaging.

Surface plasmon-coupled emission (SPCE), a novel signal enhancement technology generated by the interactions between surface plasmons and excited fluorophores in close vicinity to metallic film, has shown excellent performance in bioimaging. Variable-angle nanoplasmonic fluorescence microscopy (VANFM), based on an SPCE imaging system, can selectively modulate the imaging depth by controlling the excitation angles. In order to further improve the imaging performance, Au-Ag alloy nanoshuttles were introduced into an Au substrate to mediate the plasmonic properties. Benefiting from the strong localized plasmon effect of the modified SPCE chip, better imaging brightness, signal-to-background ratio and axial resolution for imaging of the cell membrane region were obtained, which fully displays the imaging advantages of SPCE system. Meanwhile, the imaging signal obtained from the critical angle excitation mode was also amplified, which helps to acquire a more visible image of the cell both from near- and far-field in order to comprehensively investigate the cellular interactions.

Neuroprotective effects of bis(7)-tacrine in a rat model of pressure-induced retinal ischemia.

The retinal ischemia-reperfusion model has been studied extensively and is an ideal animal model for studying clinical situations such as acute glaucoma and optic neuropathy. Our previous reports showed that bis(7)-tacrine had neuroprotective effects against glutamate-induced retinal ganglion cells damage through the drug's anti-NMDA receptor effects. Here, we investigated whether bis(7)-tacrine protects the retina from ischemic injury in a rat model. Retinal ischemia was induced by raising the intraocular pressure to 120 mmHg for 90 min. Rats received intraperitoneal injections of 0.2 mg/kg bis(7)-tacrine or saline at 30 min before ischemia, and then twice a day after retinal ischemia. Morphometric evaluation showed that bis(7)-tacrine dramatically reduced the retinal damage compared with the control group. Moreover, bis(7)-tacrine suppressed ischemia-induced reductions in a- and b-wave amplitudes of electroretinography. Protein levels of p53, the tumor suppressor gene known to induce apoptosis, were increased after ischemic injury, and treatment with bis(7)-tacrine reduced the expression of the protein. Our results suggest that bis(7)-tacrine has a neuroprotective effect against ischemic injury in the rat retina, possibly through the drug's anti-apoptotic effects. Bis(7)-tacrine may potentially be useful as a therapeutic drug in the management of ischemic retinal diseases.

Bis(7)-tacrine protects retinal ganglion cells against excitotoxicity via NMDA receptor inhibition.

AIM: To investigate whether bis(7)-tacrine, a multifunctional drug, inhibits N-methyl-D-aspartate (NMDA) -activated current in retinal ganglion cells(RGC) and provides neuroprotection against retinal cell damage. METHODS: Purified RGC cultures were obtained from retinas of 1-3 days old Sprague-Dawley(SD) rats, following a two-step immunopanning procedure. After 7 days of cultivation, the inhibition of NMDA-activated current by bis(7)-tacrine was measured by using patch-clamp recording techniques. In animal experiments, RGCs were damaged after intravitreal injection of NMDA (5µL, 40nmol) in adult rats. Bis(7)-tacrine(0.05, 0.1, 0.2mg/kg) or memantine(20mg/kg) was intraperitoneal administered to the rats fifteen minutes before intravitreally injection of NMDA. RGC damage was analyzed by histologic techniques, TUNEL and retrograde labeling techniques. RESULTS: Whole-cell patch-clamp recordings demonstrated that NMDA (30µmol/L) resulted in approximately -50 pA inward currents that were blocked by bis(7)-tacrine(1µmol/L). Histological examination and retrograde labeling analysis revealed that bis(7)-tacrine induced a significant neuroprotective effect against NMDA-induced cell damage 7 days after NMDA injection. TUNEL staining showed that pretreatment with bis(7)-tacrine was effective in ameliorating NMDA-induced apoptotic cell loss in the retinal ganglion cell layer 18 hours after injection. CONCLUSION: Bis(7)-tacrine possesses remarkable neuroprotective activities against retinal excitotoxicity through inhibition of NMDA receptors.

Neuroprotective effects of bis(7)-tacrine against glutamate-induced retinal ganglion cells damage.

BACKGROUND: Glutamate-mediated excitotoxicity, primarily through N-methyl-D-aspartate (NMDA) receptors, may be an important cause of retinal ganglion cells (RGCs) death in glaucoma and several other retinal diseases. Bis(7)-tacrine is a noncompetitive NMDA receptors antagonist that can prevent glutamate-induced hippocampal neurons damage. We tested the effects of bis(7)-tacrine against glutamate-induced rat RGCs damage in vitro and in vivo. RESULTS: In cultured neonatal rats RGCs, the MTT assay showed that glutamate induced a concentration- and time-dependent toxicity. Bis(7)-tacrine and memantine prevented glutamate-induced cell death in a concentration-dependent manner with IC50 values of 0.028 microM and 0.834 microM, respectively. The anti-apoptosis effects of bis(7)-tacrine were confirmed by annexin V-FITC/PI staining. In vivo, TUNEL analysis and retrograde labeling analysis found that pretreatment with bis(7)-tacrine(0.2 mg/kg) induced a significant neuroprotective effect against glutamate-induced RGCs damage. CONCLUSIONS: Our results showed that bis(7)-tacrine had neuroprotective effects against glutamate-induced RGCs damage in vitro and in vivo, possibly through the drug's anti-NMDA receptor effects. These findings make bis(7)-tacrine potentially useful for treating a variety of ischemic or traumatic retinopathies inclusive of glaucoma.

Evaluation of the biocompatibility of novel peptide hydrogel in rabbit eye.

A peptide containing a RGD (arginine-glycine-aspartic acid) sequence as well as a hydrophobic N-fluorenyl-9-methoxycarbonyl (FMOC) tail was prepared via a standard FMOC solid-phase peptide synthesis technique. The supramolecular self-assembly of such peptide through pi-pi stacking from FMOC tail can transfer the peptide aqueous solution into a three-dimensional hydrogel. The biocompatibility of the peptide hydrogel was evaluated via clinical follow-up and histological analysis. The data obtained demonstrated that the peptide hydrogel exhibited good biocompatibility when injected to the subconjunctival space and anterior chamber of rabbit, indicating a potential application in ophthalmology as an implantable drug delivery system for the treatment to ocular anterior segment diseases such as glaucoma, iridocyclitis, and keratopathy.

Histological observation of RGCs and optic nerve injury in acute ocular hypertension rats.

AIM: To explore the injury of retinal ganglion cells (RGCs) and optic nerves in acute ocular hypertension (OHT) rats. METHODS: We retrogradely labeled RGCs and optic nerves of Sprague-Dawley rats by injecting 20g/L fluorogold (FG) into bilateral superior colliculi. Twenty-four hours after the injection, the right eyes were performed physiological saline anterior chamber perfusion with intraocular pressure maintained at 100mmHg for 60 minutes, while the contralateral eyes were performed sham procedure as control group without elevation of the saline bottle. Retinal hematoxylin and eosin (HE) sections, retinal whole mounts and frozen sections were made 14 days later to observe the morphology and survival of RGCs. Frozen sections and transmission electron microscopy were utilized to investigate the histological manifestations of optic nerves at the same time. RESULTS: A larger number of RGCs presented in control group. It had an average density of 1995±125/mm(2) and distributed uniformly, while RGCs in OHT eyes reduced significantly to 1505±43/mm(2) compared with control group (P<0.05). The optic nerves in control group showed stronger and more uniform fluorescence on the frozen sections, and the auxiliary fibers as well as myelin sheaths were in even and intact organization by transmission electron microscopy. However, exiguous fluorescence signals, vesicular dissociation and disintegration of myelin sheaths were found in OHT group. CONCLUSION: The present study suggested that fluorogold retrograde tracing is a feasible, convenient method for quantitative and qualitative study of neuronal populations and axonal injury in acute ocular hypertension rats.