The Gliopeptide ODN, a Ligand for the Benzodiazepine Site of GABAA Receptors, Boosts Functional Recovery after Stroke.

Following stroke, the survival of neurons and their ability to reestablish connections is critical to functional recovery. This is strongly influenced by the balance between neuronal excitation and inhibition. In the acute phase of experimental stroke, lethal hyperexcitability can be attenuated by positive allosteric modulation of GABAA receptors (GABAARs). Conversely, in the late phase, negative allosteric modulation of GABAAR can correct the suboptimal excitability and improves both sensory and motor recovery. Here, we hypothesized that octadecaneuropeptide (ODN), an endogenous allosteric modulator of the GABAAR synthesized by astrocytes, influences the outcome of ischemic brain tissue and subsequent functional recovery. We show that ODN boosts the excitability of cortical neurons, which makes it deleterious in the acute phase of stroke. However, if delivered after day 3, ODN is safe and improves motor recovery over the following month in two different paradigms of experimental stroke in mice. Furthermore, we bring evidence that, during the subacute period after stroke, the repairing cortex can be treated with ODN by means of a single hydrogel deposit into the stroke cavity.SIGNIFICANCE STATEMENT Stroke remains a devastating clinical challenge because there is no efficient therapy to either minimize neuronal death with neuroprotective drugs or to enhance spontaneous recovery with neurorepair drugs. Around the brain damage, the peri-infarct cortex can be viewed as a reservoir of plasticity. However, the potential of wiring new circuits in these areas is restrained by a chronic excess of GABAergic inhibition. Here we show that an astrocyte-derived peptide, can be used as a delayed treatment, to safely correct cortical excitability and facilitate sensorimotor recovery after stroke.

Rationally designed upconversion nanoparticles for NIR light-controlled lysosomal escape and nucleus-based photodynamic therapy.

Cell nucleus-based photodynamic therapy is a highly effective method for cancer therapy, but it is still challenging to design nucleus-targeting photosensitizers. Here, we propose the "one treatment, multiple irradiations" strategy to achieve nucleus-based photodynamic therapy using the photosensitizer rose bengal (RB)-loaded and mesoporous silica-coated upconversion nanoparticles with the surface modification of amine group (UCNP/RB@mSiO2-NH2 NPs). After implementation into cancer cells, the rationally designed UCNP/RB@mSiO2-NH2 NPs could be specifically accumulated in the acidic lysosomes due to their amino group-decorated surface. Upon a short-term (3 min) irradiation of 980 nm near-infrared light, the reactive oxygen species produced by RB through the Förster resonance energy transfer between the upconversion nanoparticles and RB molecules could effectively destroy lysosomes, followed by the release of the UCNP/RB@mSiO2-NH2 NPs from the lysosomes. Subsequently, these released UCNP/RB@mSiO2-NH2 NPs could be transferred into the cell nucleus, where a second 980 nm light irradiation was conducted to achieve the nucleus-based photodynamic therapy. The rationally designed UCNP/RB@mSiO2-NH2 NPs showed excellent anticancer performance in both two-dimensional and three-dimensional cell models using the "one treatment, multiple irradiations" strategy.

Dark Antibacterial Activity of Rose Bengal.

The global spread of bacterial resistance to antibiotics promotes a search for alternative approaches to eradication of pathogenic bacteria. One alternative is using photosensitizers for inhibition of Gram-positive and Gram-negative bacteria under illumination. Due to low penetration of visible light into tissues, applications of photosensitizers are currently limited to treatment of superficial local infections. Excitation of photosensitizers in the dark can be applied to overcome this problem. In the present work, dark antibacterial activity of the photosensitizer Rose Bengal alone and in combination with antibiotics was studied. The minimum inhibitory concentrations (MIC) value of Rose Bengal against S. aureus dropped in the presence of sub-MIC concentrations of ciprofloxacin, levofloxacin, methicillin, and gentamicin. Free Rose Bengal at sub-MIC concentrations can be excited in the dark by ultrasound at 38 kHz. Rose Bengal immobilized onto silicon showed good antibacterial activity in the dark under ultrasonic activation, probably because of Rose Bengal leaching from the polymer during the treatment. Exposure of bacteria to Rose Bengal in the dark under irradiation by electromagnetic radio frequency waves in the 9 to 12 GHz range caused a decrease in the bacterial concentration, presumably due to resonant absorption of electromagnetic energy, its transformation into heat and subsequent excitation of Rose Bengal.

Neuronal gap junctions are required for NMDA receptor-mediated excitotoxicity: implications in ischemic stroke.

N-methyl-D-aspartate receptors (NMDARs) play an important role in cell survival versus cell death decisions during neuronal development, ischemia, trauma, and epilepsy. Coupling of neurons by electrical synapses (gap junctions) is high or increases in neuronal networks during all these conditions. In the developing CNS, neuronal gap junctions are critical for two different types of NMDAR-dependent cell death. However, whether neuronal gap junctions play a role in NMDAR-dependent neuronal death in the mature CNS was not known. Using Fluoro-Jade B staining, we show that a single intraperitoneal administration of NMDA (100 mg/kg) to adult wild-type mice induces neurodegeneration in three forebrain regions, including rostral dentate gyrus. However, the NMDAR-mediated neuronal death is prevented by pharmacological blockade of neuronal gap junctions (with mefloquine, 30 mg/kg) and does not occur in mice lacking neuronal gap junction protein, connexin 36. Using Western blots, electrophysiology, calcium imaging, and gas chromatography-mass spectrometry in wild-type and connexin 36 knockout mice, we show that the reduced level of neuronal death in knockout animals is not caused by the reduced expression of NMDARs, activity of NMDARs, or permeability of the blood-brain barrier to NMDA. In wild-type animals, this neuronal death is not caused by upregulation of connexin 36 by NMDA. Finally, pharmacological and genetic inactivation of neuronal gap junctions in mice also dramatically reduces neuronal death caused by photothrombotic focal cerebral ischemia. The results indicate that neuronal gap junctions are required for NMDAR-dependent excitotoxicity and play a critical role in ischemic neuronal death.

An extended logistic model of photodynamic inactivation for various levels of irradiance using the example of Streptococcus agalactiae.

Irradiance is an important factor influencing the acceleration of microorganism mortality in photodynamic inactivation (PDI) processes. Experimental observations of PDI processes indicate that the greater the irradiation power is, the faster the decrease in the population size of microorganisms. However, commonly used mathematical models of PDI processes usually refer only to specific values of irradiance without taking into account the influence of change in irradiance on the dynamic properties of inactivation. The main goal of this paper is to analyze the effect of irradiance on the PDI process and attempt to mathematically model the obtained dependencies. The analysis was carried out using the example of photodynamic inactivation of the bacterium Streptococcus agalactiae with the adopted Logistic PDI model optimized for several selected levels of irradiance. To take into account the impact of changes in irradiation power on the PDI model, the selected parameters were made appropriately dependent on this factor. The paper presents several variants of parameter modification with an evaluation of the model fitting quality criterion. The discussion on appropriate selection of parameters to be modified was carried out as a comparative analysis of several case studies. The extended logistic PDI model obtained in the conducted research effectively describes the dynamics of microorganism mortality in the whole tested irradiation power range.

Intense correlation between brain infarction and protein-conjugated acrolein.

BACKGROUND AND PURPOSE: We recently found that increases in plasma levels of protein-conjugated acrolein and polyamine oxidases, enzymes that produce acrolein, are good markers for stroke. The aim of this study was to determine whether the level of protein-conjugated acrolein is increased and levels of spermine and spermidine, the substrates of acrolein production, are decreased at the locus of infarction. METHODS: A unilateral infarction was induced in mouse brain by photoinduction after injection of Rose Bengal. The volume of the infarction was analyzed using the public domain National Institutes of Health image program. The level of protein-conjugated acrolein at the locus of infarction and in plasma was measured by Western blotting and enzyme-linked immunosorbent assay, respectively. The levels of polyamines at the locus of infarction and in plasma were measured by high-performance liquid chromatography. RESULTS: The level of protein-conjugated acrolein was greatly increased, and levels of spermine and spermidine were decreased at the locus of infarction at 24 hours after the induction of stroke. The size of infarction was significantly decreased by N-acetylcysteine, a scavenger of acrolein. It was also found that the increases in the protein-conjugated acrolein, polyamines, and polyamine oxidases in plasma were observed after the induction of stroke. CONCLUSIONS: The results indicate that the induction of infarction is well correlated with the increase in protein-conjugated acrolein at the locus of infarction and in plasma.

Electrospun oral formulations for combined photo-chemotherapy of colon cancer.

In this work, we report new formulations for the combined photo-chemotherapy of colon cancer. Fibers were fabricated via coaxial-electrospinning with the intent of targeting delivery of the anti-cancer drug carmofur (CAR) and the photosensitizer rose bengal (RB) selectively to the colon site. The fibers comprised a hydroxypropyl methylcellulose (HPMC) core loaded with the active ingredients, and a pH-sensitive Eudragit L100-55 shell. The fibers were found to be homogeneous and cylindrical and have visible core-shell structures. X-ray diffraction and differential scanning calorimetry demonstrated that both CAR and RB were present in the fibers in the amorphous physical form. In vitro drug release studies showed that the fibers have the potential to selectively deliver drugs to the colon, with only 10-15 % release noted in the acidic conditions of the stomach but sustained release at pH 7.4. Cytotoxicity studies were undertaken on human dermal fibroblast (HDF) and colon cancer (Caco-2) cells, and the influence of light on cell death was also explored. The fibers loaded with CAR alone showed obvious toxicity to both cell lines, with and without the application of light. The RB-loaded fibers led to high viability (ca. 80% for both cell types) in the absence of light, but much greater toxicity was noted (30-50%) with light. The same trends were observed with the formulation containing both CAR and RB, but with lower viabilities. The RB and RB/CAR loaded systems show clear selectivity for cancerous over non-cancerous cells. Finally, mucoadhesion studies revealed there were strong adhesive forces between the rat colonic mucosa and the fibers after they had passed through an acidic environment. Such electrospun fibers thus could have potential in the development of oral therapies for colon cancer.

5-Methyltetrahydrofolate inhibits photosensitization reactions and strand breaks in DNA.

The known functions of folate are to support one-carbon metabolism and to serve as photoreceptors for cryptochromes and photolyases. We demonstrate that 5-methyltetrahydrofolate (5-MTHF, the predominant folate in plasma) is also a potent, near diffusion limited, scavenger of singlet oxygen and quencher of excited photosensitizers. Both pathways result in decomposition of 5-MTHF, although ascorbate can protect against this loss. In the absence of photosensitizers, 5-MTHF is directly decomposed only very slowly by UVA or UVB. Although synthetic folic acid can promote DNA damage by UVA, submicromolar 5-MTHF inhibits photosensitization-induced strand breaks. These observations suggest a new role for reduced folate in protection from ultraviolet damage and have bearing on the hypothesis that folate photodegradation influenced the evolution of human skin color.

Influence of melatonin pretreatment and preconditioning by hypobaric hypoxia on the development of cortical photothrombotic ischemic lesion.

Photothrombotic model of ischemia (PT) is based on free radical-mediated endothelial dysfunction followed by thrombosis. Free radicals are also involved in hypoxic preconditioning. We tested the sensitivity of PT to preconditioning with hypobaric hypoxia and to pretreatment with melatonin. In adult Wistar rats, after intravenous application of Rose Bengal, a stereo-tactically defined spot on the denuded skull was irradiated by a laser for 9 min. The first experimental group underwent hypobaric hypoxia three days before irradiation. In the second experimental group, melatonin was applied intraperitoneally one hour before irradiation. Three days after irradiation, animals were sacrificed, the brains perfused, and stained with TTC. Ischemic lesions were divided into grades (I, II, III). In the control group (where no manipulation preceded photothrombosis), most animals displayed deep damage involving the striatum (grade III). The group pre-exposed to hypoxia showed similar results. Only 28.57 % of the melatonin pretreated animals exhibited grade III lesions, and in 57.14 % no signs of lesions were detected. Pre-exposure to hypoxia was not protective in our model. Pretreatment with melatonin lead to a significant reduction of the number of large ischemic lesions. This result is probably caused by protection of endothelial cells by melatonin.

Photolytic decolorization of Rose Bengal by UV/H(2)O(2) and data optimization using response surface method.

Rose Bengal (C.I. name is Acid Red 94) was irradiated with UV light in the presence of hydrogen peroxide. The photoinduced decolorization of the dye was monitored spectrophotometrically. The apparent rate of decolorization was calculated from the observed absorption data and was found to be pseudo first order. A systematic study of the effect of dye concentration and H(2)O(2) concentration on the kinetics of dye decolorization was also carried out. Dye decolorization increased with increasing H(2)O(2) concentration and decreasing dye concentration. The maximum dye decolorization was determined as 90% with 0.005 mM dye at optimum 0.042 M H(2)O(2) and pH 6.6. Additionally, the effect on decolorization of this dye in the presence of some additives (ions) was also investigated. It was seen that sulphite caused a maximum effect on % decolorization of the dye solution. A plausible explanation involving the probable radical initiated mechanism was given to explain the dye decolorization. The experimental data was also optimized using the response surface methodology (RSM). According to ANOVA results, the proposed model can be used to navigate the design space. It was found that the response of Rose Bengal degradation is very sensitive to the independent factors of dye concentration, H(2)O(2) concentration, pH and reaction time. The proposed model for D-optimal design fitted very well with the experimental data with R(2) and R(adj)(2) correlation coefficients of 0.85 and 0.80, respectively.

Biocompatible, drug-loaded anti-adhesion barrier using visible-light curable furfuryl gelatin derivative.

Recently, many of studies have been attempted to determine how to decrease adhesion. To effectively prevent adhesion, decrease in unnecessary surgical procedures, prevention of contact with other tissue, and drug treatment for inflammation are required. However, current anti-adhesion materials have disadvantages. To solve current problems, we prepared a biocompatible drug-loaded anti-adhesion barrier using a visible-light curable furfuryl gelatin derivative. We used riboflavin as a photo-initiator in the photo-curing process. The biocompatibility of riboflavin was estimated compared with that of Rose Bengal. In addition, the curing ratio was measured to determine whether riboflavin initiated photo-curing. We also evaluated the curing ratio of riboflavin according to the concentration of F-gelatin and the photo-irradiation time. A drug used to decrease inflammation that causes adhesion should not disappear from the surgical site and should also be released consistently. For this, we observed the release profiles of photo-immobilized ibuprofen with different concentrations of F-gelatin. Because an anti-adhesion barrier should protect from bacterial infection we evaluated the protective ability of a barrier formed by F-gelatin. In conclusion, a drug-loaded anti-adhesion barrier was prepared using a visible-light curable furfuryl gelatin derivative, with riboflavin as a photo-initiator. We expect that this drug-loaded anti-adhesion barrier effectively decrease adhesion formation.

Epileptogenesis after cortical photothrombotic brain lesion in rats.

We investigated epileptogenesis after cortical photothrombotic stroke induced with Rose Bengal dye in adult Sprague-Dawley rats. To detect spontaneous seizures, video-electroencephalograms were recorded at 2, 4, 6, 8, and 10 months for 7-14 days (24 h/day). At the end, spatial and emotional learning and memory were assessed using the Morris water-maze and fear-conditioning test, respectively, and the brains were processed for histologic analysis. Seizures were detected in 18% of rats that received photothrombosis. The average seizure frequency was 0.39 seizures per recording day and mean seizure duration was 117 s. Over 60% of seizures occurred during the dark hours. Rats with photothrombotic lesions were impaired in the water-maze (P<0.05) but not in the fear-conditioning test as compared with controls. Histology revealed that lesion depth varied from cortical layers I to VI in photothrombotic rats with epilepsy. Epileptic rats had light mossy fiber sprouting in the inner molecular layer of the dentate gyrus both ipsilateral and contralateral to the lesion. This study extends the current understanding of epileptogenesis and functional impairment after cortical lesions induced by photothrombosis. Our observations support the hypothesis that photothrombotic stroke in rats is a useful animal model for investigating the mechanisms of post-stroke epileptogenesis.

Singlet molecular oxygen application for 2-chlorophenol removal.

A special kind of photocatalysis-a photosensitized oxidation involving singlet molecular oxygen ((1)O(2)) was applied to decomposition of 2-chlorophenol (2-CP) in water solution. The photoprocess was carried out in a homo- and heterogeneous system using rose bengal (RB) as a sensitizer. In the homogeneous solution the influence of initial 2-CP concentration and pH on reaction rate was observed. Based on the kinetic model, the rate constants of (1)O(2) quenching and reaction with 2-CP and the rate constant of excited sensitizer quenching by 2-CP were determined. In the heterogeneous system, silane gel was a carrier for the immobilized sensitizer. In order to estimate kinetic parameters, an attempt was made to describe the process using Langmuir-Hinshelwood (L-H) type mechanism. The Langmuir equilibrium constants for oxygen and 2-CP adsorbed on the gel surface were also estimated.

Uniform field loop-gap resonator and rectangular TEU02 for aqueous sample EPR at 94GHz.

In this work we present the design and implementation of two uniform-field resonators: a seven-loop-six-gap loop-gap resonator (LGR) and a rectangular TEU02 cavity resonator. Each resonator has uniform-field-producing end-sections. These resonators have been designed for electron paramagnetic resonance (EPR) of aqueous samples at 94GHz. The LGR geometry employs low-loss Rexolite end-sections to improve the field homogeneity over a 3mm sample region-of-interest from near-cosine distribution to 90% uniform. The LGR was designed to accommodate large degassable Polytetrafluorethylen (PTFE) tubes (0.81mm O.D.; 0.25mm I.D.) for aqueous samples. Additionally, field modulation slots are designed for uniform 100kHz field modulation incident at the sample. Experiments using a point sample of lithium phthalocyanine (LiPC) were performed to measure both the uniformity of the microwave magnetic field and 100kHz field modulation, and confirm simulations. The rectangular TEU02 cavity resonator employs over-sized end-sections with sample shielding to provide an 87% uniform field for a 0.1×2×6mm3 sample geometry. An evanescent slotted window was designed for light access to irradiate 90% of the sample volume. A novel dual-slot iris was used to minimize microwave magnetic field perturbations and maintain cross-sectional uniformity. Practical EPR experiments using the application of light irradiated rose bengal (4,5,6,7-tetrachloro-2',4',5',7'-tetraiodofluorescein) were performed in the TEU02 cavity. The implementation of these geometries providing a practical designs for uniform field resonators that continue resonator advancements towards quantitative EPR spectroscopy.

Characterization of a novel thrombotic middle cerebral artery occlusion model in monkeys that exhibits progressive hypoperfusion and robust cortical infarction.

In an attempt to establish a thrombotic middle cerebral artery (MCA) occlusion model using cynomolgus monkeys, we measured the blood flow in the main MCA tract and cerebral cortex, brain damage, and neurological deficits, and compared them with those of mechanical MCA occlusion model. Thrombotic occlusion was induced photochemically by green light application on the MCA following rose bengal treatment; mechanical occlusion was induced by MCA clipping for 3h. Patency of the main MCA tract showed two patterns in the thrombotic model: permanent occlusion or cyclical flow reduction (CFR). Regional cerebral blood flow (rCBF) decreased during occlusion followed by post-ischemic hyperperfusion in the clipping model, whereas rCBF reduction expanded time-dependently in the thrombotic occlusion model. Brain infarction and neurological scores in the thrombotic occlusion model were significantly larger than those in the clipping occlusion model. In histological assessment, microthrombi containing myeloperoxidase- and fibrinogen-positive cells were observed in the cortex following the thrombotic but not clipping occlusion. These results collectively suggest that this thrombotic MCA occlusion model, because it shows impairment of cerebral microcirculation, could provide a vital platform for understanding progressive ischemia as well as for evaluating potential therapeutic drugs.

Sensitized photooxidation of thyroidal hormones. Evidence for heavy atom effect on singlet molecular oxygen [O2(1Deltag)]-mediated photoreactions.

Thyronine derivatives are essential indicators of thyroid gland diseases in clinical diagnosis and are currently used as standards for developing ordinary biochemical assays. Photooxidation of gland hormones of the thyronine (TN) family and structurally related compounds (TN, 3,5-diiodothyronine,3,3',5-triiodothyronine and 3,3',5,5'-tetraiodothyronine or thyroxine) was studied using rose bengal, eosin and perinaphthenone (PN) as dye sensitizers. Tyrosine (Tyr) and two iodinated derivatives (3-iodotyrosine and 3,5-diiodotyrosine) were also included in the study for comparative purposes. Irradiation of aqueous solutions of substrates containing xanthene dyes with visible light triggers a complex series of competitive interactions, which include the triplet excited state of the dye (3Xdye*) and singlet molecular oxygen [O2(1Deltag)]-mediated and superoxide ion-mediated reactions. Rate constants for interaction with the 3Xdye*, attributed to an electron transfer process, are in the order of 10(8)-10(9) M-1 s-1 depending on the dye and the particular substrate. The photosensitization using PN follows a pure Type-II (O2(1Deltag) mediated) mechanism. The presence of the phenolic group in Tyr, TN and iodinated derivatives dominates the kinetics of photooxidation of these compounds. The reactive rate constants, k(r), and the quotient between reactive and overall rate constants (k(r)/k(t) values, in the range of 0.7-0.06) behave in an opposite fashion compared with the overall rate constants and oxidation potentials. This apparent inconsistency was interpreted on the basis of an internal heavy atom effect, favoring the intersystem-crossing deactivation route within the encounter complex with the concomitant reduction of effective photooxidation.

Photo-induced inhibition of Alzheimer's ß-amyloid aggregation in vitro by rose bengal.

The abnormal aggregation of ß-amyloid (Aß) peptides in the brain is a major pathological hallmark of Alzheimer's disease (AD). The suppression (or alteration) of Aß aggregation is considered to be an attractive therapeutic intervention for treating AD. We report on visible light-induced inhibition of Aß aggregation by xanthene dyes, which are widely used as biomolecule tracers and imaging markers for live cells. Among many xanthene dyes, rose bengal (RB) under green LED illumination exhibited a much stronger inhibition effect upon photo-excitation on Aß aggregation than RB under dark conditions. We found that RB possesses high binding affinity to Aß; it exhibits a remarkable red shift and a strong enhancement of fluorescence emission in the presence of Aß. Photo-excited RB interfered with an early step in the pathway of Aß self-assembly and suppressed the conformational transition of Aß monomers into ß-sheet-rich structures. Photo-excited RB is not only effective in the inhibition of Aß aggregation, but also in the reduction of Aß-induced cytotoxicity.

Photodynamic action of rose bengal on isolated rat pancreatic acini: stimulation of amylase release.

The halogenated fluorescein derivative, rose bengal, upon photon activation, elicits amylase secretion from isolated, perifused pancreatic acini. This effect is due to production of highly reactive singlet delta oxygen which can permeabilize the cell membrane and may also react chemically with secretagogue receptors, or other functional components of the membrane such as the G-proteins. The profile of photodynamically induced amylase secretion is anion-dependent: it becomes biphasic when the chloride ion is substituted by the glutamate ion, an effect attributed to the action of glutamate on the ionic transport systems of the zymogen granule membrane.

Photodynamic retinal vascular thrombosis. Rate and duration of vascular occlusion.

Dye-sensitized photochemical thrombosis is a new method of producing vascular occlusion in the eye for experimental purposes. The rate and duration of photodynamic occlusions of branch retinal vessels was measured in pigmented and albino rat eyes after intravenous injection of the photosensitizing dye, rose bengal. Selected vessels were exposed to focused, white light until vascular occlusion was observed biomicroscopically. A slit lamp was used for a light source in this procedure, allowing adjustment of spot size, shape, and orientation. Arterioles occluded more rapidly than venules, and the time required to produce vascular occlusion decreased when animals breathed pure oxygen administered by face mask. Rose bengal doses of 40 and 80 mg/kg were effective, 20 mg/kg was partially effective, and 1 and 10 mg/kg were ineffective in producing branch arteriole occlusion at a light intensity of 73.5 mW/cm2. The total light energy required to produce occlusion increased from an average of 0.06 J using 80 mg/kg to 0.50 J using 20 mg/kg of rose bengal. Lower light intensities produced vessel occlusion less rapidly (46 mW/cm2) or not at all (17.5 mW/cm2). The rate of retinal arteriolar occlusion was not affected by ocular pigmentation. The duration of branch vessel occlusion depended on length of vessel treated and did not exceed 3 days in arterioles and 4 days in venules. Histologic sections showed discrete areas of retinal and choroidal vascular thrombosis confined to the area of direct light exposure. Choroidal vascular thrombosis and outer retinal damage predominated in eyes treated at low light intensity. Thrombosis usually extended into the deep choroidal vessels in albino but not pigmented eyes.(ABSTRACT TRUNCATED AT 250 WORDS)

Photochemical keratodesmos for bonding corneal incisions.

PURPOSE: To evaluate the immediate and long-term effectiveness of a dye-plus-laser irradiation treatment (photochemical keratodesmos [PKD]) for sealing corneal incisions. METHODS: Incisions (3.5 mm) in rabbit corneas were treated on the incision walls with rose bengal dye followed by exposure to 514-nm laser radiation. PKD was evaluated in three groups (n = 3-6) using laser fluences of 115, 153, or 192 J/cm(2) (180-, 240-, and 300- second exposures, respectively) compared with an untreated group (n = 8). The intraocular pressure at which leakage occurred (IOP(L)) during infusion of saline into the anterior chamber was determined. In a long-term study, treated and control corneas were observed weekly for 10 weeks for the appearance of neovascularization, anterior chamber inflammation, iridocorneal adhesion, corneal melting, and scarring. RESULTS: Immediately after treatment, the IOP(L) increased with increasing laser fluence, producing IOPs of 230 +/- 90, 370 +/- 120, and more than 500 mm Hg at 115, 153, and 192 J/cm(2), respectively, compared with 40 +/- 20 mm Hg in control eyes (P < 0.005). No reduction in the IOP(L) was observed up to 14 days after surgery. Corneal melting in PKD-treated or control eyes was not observed in the 10-week healing study. Neovascularization, which peaked at 4 weeks but resolved by 8 weeks, was detected around the incision in both PKD-treated and control eyes. CONCLUSIONS: Immediate and lasting sealing of corneal incisions was obtained in eyes treated with PKD, using short irradiation times. These results suggest that PKD has potential for improved corneal tissue bonding.