Transepithelial versus epithelium-off corneal crosslinking for progressive keratoconus.

BACKGROUND: Keratoconus is the most common corneal dystrophy. It can cause loss of uncorrected and best-corrected visual acuity through ectasia (thinning) of the central or paracentral cornea, irregular corneal scarring, or corneal perforation. Disease onset usually occurs in the second to fourth decade of life, periods of peak educational attainment or career development. The condition is lifelong and sight-threatening. Corneal collagen crosslinking (CXL) using ultraviolet A (UVA) light applied to the cornea is the only treatment that has been shown to slow progression of disease. The original, more widely known technique involves application of UVA light to de-epithelialized cornea, to which a photosensitizer (riboflavin) is added topically throughout the irradiation process. Transepithelial CXL is a recently advocated alternative to the standard CXL procedure, in that the epithelium is kept intact during CXL. Retention of the epithelium offers the putative advantages of faster healing, less patient discomfort, faster visual rehabilitation, and less risk of corneal haze. OBJECTIVES: To assess the short- and long-term effectiveness and safety of transepithelial CXL compared with epithelium-off CXL for progressive keratoconus. SEARCH METHODS: To identify potentially eligible studies, we searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Trials Register) (2020, Issue 1); Ovid MEDLINE; Embase.com; PubMed; Latin American and Caribbean Health Sciences Literature database (LILACS); ClinicalTrials.gov; and World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP). We did not impose any date or language restrictions. We last searched the electronic databases on 15 January 2020. SELECTION CRITERIA: We included randomized controlled trials (RCTs) in which transepithelial CXL had been compared with epithelium-off CXL in participants with progressive keratoconus. DATA COLLECTION AND ANALYSIS: We used standard Cochrane methodology. MAIN RESULTS: We included 13 studies with 723 eyes of 578 participants enrolled; 13 to 119 participants were enrolled per study. Seven studies were conducted in Europe, three in the Middle East, and one each in India, Russia, and Turkey. Seven studies were parallel-group RCTs, one study was an RCT with a paired-eyes design, and five studies were RCTs in which both eyes of some or all participants were assigned to the same intervention. Eleven studies compared transepithelial CXL with epithelium-off CXL in participants with progressive keratoconus. There was no evidence of an important difference between intervention groups in maximum keratometry (denoted 'maximum K' or 'Kmax'; also known as steepest keratometry measurement) at 12 months or later (mean difference (MD) 0.99 diopters (D), 95% CI -0.11 to 2.09; 5 studies; 177 eyes; I2 = 41%; very low certainty evidence). Few studies described other outcomes of interest. The evidence is very uncertain that epithelium-off CXL may have a small (data from two studies were not pooled due to considerable heterogeneity (I2 = 92%)) or no effect on stabilization of progressive keratoconus compared with transepithelial CXL; comparison of the estimated proportions of eyes with decreases or increases of 2 or more diopters in maximum K at 12 months from one study with 61 eyes was RR 0.32 (95% CI 0.09 to 1.12) and RR (non-event) 0.86 (95% CI 0.74 to 1.00), respectively (very low certainty). We did not estimate an overall effect on corrected-distance visual acuity (CDVA) because substantial heterogeneity was detected (I2 = 70%). No study evaluated CDVA gain or loss of 10 or more letters on a logarithm of the minimum angle of resolution (logMAR) chart. Transepithelial CXL may result in little to no difference in CDVA at 12 months or beyond. Four studies reported that either no adverse events or no serious adverse events had been observed. Another study noted no change in endothelial cell count after either procedure. Moderate certainty evidence from 4 studies (221 eyes) found that epithelium-off CXL resulted in a slight increase in corneal haze or scarring when compared to transepithelial CXL (RR (non-event) 1.07, 95% CI 1.01 to 1.14). Three studies, one of which had three arms, compared outcomes among participants assigned to transepithelial CXL using iontophoresis versus those assigned to epithelium-off CXL. No conclusive evidence was found for either keratometry or visual acuity outcomes at 12 months or later after surgery. Low certainty evidence suggests that transepithelial CXL using iontophoresis results in no difference in logMAR CDVA (MD 0.00 letter, 95% CI -0.04 to 0.04; 2 studies; 51 eyes). Only one study examined gain or loss of 10 or more logMAR letters. In terms of adverse events, one case of subepithelial infiltrate was reported after transepithelial CXL with iontophoresis, whereas two cases of faint corneal scars and four cases of permanent haze were observed after epithelium-off CXL. Vogt's striae were found in one eye after each intervention. The certainty of the evidence was low or very low for the outcomes in this comparison due to imprecision of estimates for all outcomes and risk of bias in the studies from which data have been reported. AUTHORS' CONCLUSIONS: Because of lack of precision, frequent indeterminate risk of bias due to inadequate reporting, and inconsistency in outcomes measured and reported among studies in this systematic review, it remains unknown whether transepithelial CXL, or any other approach, may confer an advantage over epithelium-off CXL for patients with progressive keratoconus with respect to further progression of keratoconus, visual acuity outcomes, and patient-reported outcomes (PROs). Arrest of the progression of keratoconus should be the primary outcome of interest in future trials of CXL, particularly when comparing the effectiveness of different approaches to CXL. Furthermore, methods of assessing and defining progressive keratoconus should be standardized. Trials with longer follow-up are required in order to assure that outcomes are measured after corneal wound-healing and stabilization of keratoconus. In addition, perioperative, intraoperative, and postoperative care should be standardized to permit meaningful comparisons of CXL methods. Methods to increase penetration of riboflavin through intact epithelium as well as delivery of increased dose of UVA may be needed to improve outcomes. PROs should be measured and reported. The visual significance of adverse outcomes, such as corneal haze, should be assessed and correlated with other outcomes, including PROs.

Chitosan-riboflavin composite film based on photodynamic inactivation technology for antibacterial food packaging.

Photodynamic inactivation (PDI) is a novel sterilization technology that has proven effective in medicine. This study focused on applying PDI to food packaging, where chitosan (CS) films containing photosensitizing riboflavin (RB) were prepared via solution casting. The CS-RB composite films exhibited good ultraviolet (UV)-barrier properties, and had a visually appealing highly transparent yellow appearance. Scanning electron microscopy (SEM) confirmed even dispersion of RB throughout the CS film. The addition of RB led to improved film characteristics, including the thickness, mechanical properties, solubility, and water barrier properties. The CS-RB5 composite films produced sufficient singlet oxygen under blue LED irradiation for 2 h to inactivate two food-borne pathogens (Listeria monocytogenes and Vibrio parahaemolyticus) and one spoilage bacteria (Shewanella baltica). The CS-RB composite films were assessed as a salmon packaging material, where inhibition of bacterial growth was observed. The film is biodegradable, and has the potential to alleviate the issues associated with the excessive use of petrochemical materials, such as environmental pollution and limited resources. The CS-RB composite films showed potential as a novel environmentally friendly packaging material for shelf-life extension of refrigerated food products.

Corneal cross-linking versus standard care in children with keratoconus - a randomised, multicentre, observer-masked trial of efficacy and safety (KERALINK): a statistical analysis plan.

BACKGROUND: The KERALINK trial tests the hypothesis that corneal cross-linking (CXL) treatment reduces the progression of keratoconus in comparison to standard care in patients aged 10-16 years. This article describes the statistical analysis plan for this trial as an update to the published protocol. It is written before the end of the patient follow-up, while the outcome of the trial is still unknown. DESIGN AND METHODS: KERALINK is a randomised controlled, observer-masked, multicentre trial in progressive keratoconus comparing epithelium-off CXL with standard care, including spectacles or contact lenses as necessary for best-corrected acuity. Keratoconus is a disorder of the shape of the cornea in which the normally round dome-shaped clear front window of the eye (cornea) thins progressively leading to a cone-like bulge. This impairs the ability of the eye to focus properly, causing reduced vision which requires spectacle or contact lens wear or, in a minority of patients, eventually corneal replacement by a transplant for best vision. The primary outcome measure is the between-group difference in K2 at 18 months adjusted for K2 at baseline examination. K2 is the value of the steepest corneal meridian as measured on Pentacam topography. Secondary outcomes are keratoconus progression, time to keratoconus progression, visual acuity, refraction, apical corneal thickness and adverse events. Patient-reported effects will be explored by questionnaires. We describe in detail the statistical aspects of KERALINK: the outcome measures, the sample size calculation, general analysis principles, the planned descriptive statistics and statistical models, and planned subgroup and sensitivity analyses. DISCUSSION: The KERALINK statistical analysis will provide comprehensive and precise information on the relative effectiveness of the two treatments. The plan will be implemented in May 2020 when follow-up for the trial is completed. TRIAL REGISTRATION: EudraCT, 2016-001460-11. Registered on 19 May 2016.

An uncommon use of irradiated flavins: Brønsted acid catalysis.

We present that thioacetalization of aldehydes can be induced by blue light irradiation in the presence of a catalytic amount of riboflavin tetraacetate (RFTA) under aerobic conditions. Several control experiments have suggested that the reaction is more likely to be catalyzed by acidic species generated in situ upon light irradiation. We have proposed that single electron transfer from a thiol (RSH) to the excited state of RFTA can take place to give a one-electron oxidized thiol (RSH+˙) and the one-electron reduced RFTA (RFTA-˙), which can be trapped by molecular oxygen to be stabilized as Brønsted acids including the protonated RFTA-˙ (RFTAH˙). Finally, we have demonstrated that such acidic species can be prepared in advance as a solution and used as Brønsted acid catalysts for not only thioacetalization but also Mannich-type reactions.

Analysis of photoreactivity and phototoxicity of riboflavin's analogue 3MeTARF.

Recent studies focus on usage of blue light of λ = 450 nm in combination with photosensitizers to treat surface skin disorders, including cancers. In search of convenient therapeutic factor we studied riboflavin analogue 3-methyl-tetraacetylriboflavin (3MeTARF) as potential sensitizer. Riboflavin (Rfl) itself, non -toxic in the darkness, upon absorption of UVA and blue light, may act as photosensitizer. However, Rfl efficiency is limited due to its susceptibility to photodecomposition. Riboflavin's acetylated analogue, 3MeTARF, bears substituents in ribose chain, which inhibit intramolecular processes leading to degradation. Upon excitation, this compound, reveals higher photochemical resistance, remaining a good singlet oxygen generator. Thus, being more stable as the sensitizer, might be much more efficient in photodynamic processes. The objective of undertaken study was to elucidate mechanisms of 3MeTARF photoreactivity under the irradiation with blue light in comparison to its mater compound, riboflavin. We approached this goal by using spectroscopic methods, like direct singlet oxygen phosphorescence detection at 1270 nm, EPR spin trapping and oximetry. Additionally, we tested both riboflavin and 3MeTARF phototoxicity against melanoma cells (WM115) and we studied mechanism of photodynamic cell death, as well. Moreover, 3MeTARF induces apoptosis in melanoma cells at ten times lower concentration than riboflavin itself. Our studies confirmed that 3MeTARF remains stable upon blue light activation and is more efficient photosensitizer than Rfl.

Improvement of myofibrillar protein gel strength of Scomberomorus niphonius by riboflavin under UVA irradiation.

In this study, effects of different concentrations of riboflavin (0, 0.02, and 0.1 µmol/g protein) on myofibrillar protein (MP, Scomberomorus niphonius) gel were characterized. The gel structure and properties were studied with or without Ultraviolet A (UVA) irradiation. Electron spin resonance results showed that riboflavin produced ·OH under UVA irradiation, which subsequently oxidized the MP. Compared with the control group, the addition of riboflavin with UVA irradiation increased the strength of the MP gel. The rheological results showed that under UVA irradiation, addition of riboflavin facilitated the sol-gel transition between 45 and 52°C, indicating that oxidation led to significant structural changes which in turn resulted in a more compact and uniform gel network. The presence of riboflavin led to increased carbonyl content and decreased sulfhydryl and free amino groups, which decreased the protein solubility and promoted alpha-helical conformational loss in the secondary structure of the MP. These results all indicated that the MP has been oxidized. Electrophoresis revealed that myosin heavy chains were aggregated in the UVA-treated riboflavin-added MP gel, indicating that protein cross-linking has been induced. All the results indicated that the ·OH produced by riboflavin under UVA irradiation oxidized the MP, and improved protein crosslinking and gel properties.

A randomised, controlled, observer-masked trial of corneal cross-linking for progressive keratoconus in children: the KERALINK protocol.

INTRODUCTION: The KERALINK trial tests the hypothesis that corneal cross-linking (CXL) treatment reduces the progression of keratoconus in comparison to standard care in patients under 17 years old. KERALINK is a randomised controlled, observer-masked, multicentre trial in progressive keratoconus comparing epithelium-off CXL with standard care, including spectacles or contact lenses as necessary for best-corrected acuity. METHODS AND ANALYSIS: A total of 30 participants will be randomised per group. Eligible participants aged 10-16 years with progressive keratoconus in one or both eyes will be recruited. Following randomisation, participants will be followed up 3-monthly for 18 months. The effect on progression will be determined by K2 on corneal topography. The primary outcome measure is between-group difference in K2 at 18 months adjusted for K2 at baseline examination. Secondary outcomes are the effect of CXL on (1) keratoconus progression, (2) time to keratoconus progression, (3) visual acuity, (4) refraction, (5) apical corneal thickness and (6) adverse events. Patient-reported effects will be explored by questionnaires. ETHICS AND DISSEMINATION: Research Ethics Committee Approval was obtained on 30 June 2016 (ref: 14/LO/1937). Current protocol: V.5.0 (08/11/2017). Study findings will be published in peer-reviewed journals. TRIAL REGISTRATION NUMBER: European Union clinial trials register (EudraCT) 2016-001460-11.

Towards the understanding of the UV light, riboflavin and additive solution contributions to the in vitro lesions observed in Mirasol®-treated platelets.

OBJECTIVES: Pathogen reduction technologies are implemented to increase the safety of blood products. We previously showed that the UVB alone significantly contributes to the storage lesions observed in platelets treated with riboflavin/UVB using a home-made illuminator. The present study aims at confirming these observations using the commercial Mirasol® technology. METHODS: A three-arm study (untreated, UV-, Mirasol®-treated platelets) was conducted to investigate the platelet storage lesions throughout storage (n=4). A two-arm study was then designed to compare Intersol and T-PAS+ additive solutions (n=3). Phenotype and functional platelet characteristics were assessed using flow cytometry, aggregometry, antioxidant assays and metabolic parameters. RESULTS: Mirasol®-treated platelets exhibit enhanced storage lesions compared to controls (increase of activation markers and glycolysis rate, lower hypotonic shock and double-agonist activation responses, and decrease of total antioxidant capacity). Here, we also confirmed that the UV radiation alone is causing platelet lesions. Riboflavin tends to have an intracellular protective role while it decreases the extracellular antioxidant defenses. Furthermore, benefits of platelet additive solutions containing potassium and magnesium were confirmed as it reduces the extent of storage lesions. CONCLUSIONS: The photosensitizer, UV illumination and composition of the platelet additive solutions are key parameters influencing the platelet storage lesion. The clinical relevance of these findings is not fully understood and recent published clinical studies could not show increase in bleeding in patients receiving Mirasol-treated platelets. New developments in storage solutions might help to improve storage conditions of PRT-treated platelets and should be prioritised as research subject in the future.

A comparative insight into the oxidative damage and cell death potential of photoilluminated aminophylline - riboflavin system in normal and cancer lung cells of swiss albino mice.

Photosensitisation of riboflavin (Rf) activates aminophylline (Am) resulting into the formation of a highly pro-oxidant Am-Rf system. We have previously shown its macromolecular damaging response in human peripheral lymphocytes, however, its potential inside a cancer cell is yet to be explored. Since, altered redox status of a cancer cell is a reliable therapeutic window in designing anticancer strategies, therefore, it's imperative to investigate whether the reactive oxygen species (ROS) generated by this system readily triggers apoptosis or it is countered by elevated antioxidant machinery of a cancer cell. Here, we have demonstrated DNA damaging and cytotoxic potential of this system in benzopyrene induced lung carcinoma cells. Using various biochemical assays significant macromolecular damage was observed along with mitochondrial membrane disruption as evaluated by rhodamine 6G membrane permeant. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay showed decreased cell viability, confirming cytotoxic action whereas fluorescence and electron microscopic evaluation confirmed apoptosis. ROS scavengers ameliorated the oxidative damage and inhibited cell death, thus confirming, pivotal role of ROS in causing cell death. It was evidently found out that the lung cancer cells were more sensitive towards the photodynamic action of this system, which can be attributed to the upregulated riboflavin metabolism in cancer cell. Hence, we propose a photodynamic mechanism to kill lung cancer cell that exhibits enhanced sensitivity towards cancer cells.

Oxidation of cystatin imparted by riboflavin generated free radicals: Spectral analysis.

Thiol Protease inhibitors (cystatins) are endogenous natural inhibitors of cysteine proteases. They are present in all mammalians cells and body fluids. Cystatin are allocated into three major families. Family -I stefins, family -II cystatins and family -III kininogens, according to their amino acid sequence, molecular weight, carbohydrate content and disulphide bonds. It has been investigated that thiol proteases (cathepsin) and their endogenous inhibitor, cystatins have been closely associated with diseases like Alzheimer's, Prions, neurodegenerative diseases, cancer and diabetes. Photodynamic effect of various sensitizers' have long been applied to delineate structural and functional properties of biologically active proteins. Flavins are well known to photo oxidize amino acids which effects conformation of proteins. Riboflavin (Vit B2) with a recommended daily requirement of approximately 2-3 mg is a yellow pigment, It is widely distributed in human tissues and blood, in both free and conjugated forms. In the present Study it has been shown that cystatin purified from buffalo brain (BC) is susceptible to reactive oxygen species generated by photo activation of riboflavin. It was observed that Photo activated riboflavin leads to inactivation of BC. Major Loss of tryptophan intensity was observed in the presence of purified thiol protease inhibitor upon incubation with 50 µM of riboflavin. In order to inspect the type of reactive oxygen species involved in inactivation of the inhibitor, different scavenger's were used namely glucose, potassium Iodide, sodium azide, manitol, thiourea, sodium benzoate, curcumin, quercetin, ascorbic acid and uric acid. It was found that Glucose, Potassium Iodide and sodium azide, have preventive effect on photo inactivation of the purified cystatin whilst other scavengers illustrated diminutive defensive effect.

Pathogen reduction combined with rapid diagnostic tests to reduce the risk of transfusion-transmitted infections in Uganda.

BACKGROUND: Blood safety and transfusion-transmitted infections (TTIs) are a major concern in low-resource areas. Laboratory screening of donors, a key contributor to blood safety, is usually done by enzyme-linked immunosorbent assay (ELISA) methods, which use expensive reagents and necessitate complex instruments and sophisticated laboratory staff. Rapid diagnostic tests (RDTs) are less expensive and easier to perform but have less sensitivity. Pathogen reduction technology (PRT) reduces transfusion transmission of malaria and may be effective in decreasing other TTIs. We explored the potential to improve blood safety by combining PRT and RDTs in comparison with current ELISA testing. STUDY DESIGN AND METHODS: We identified the sensitivity of RDTs available in Uganda and the sensitivity of currently used ELISA. Data from a riboflavin-and-UV-based photochemical treatment PRT were used. Human immunodeficiency virus (HIV), hepatitis B virus (HBV), hepatitis C virus (HCV), and malaria were studied. Probability models were developed for estimation of the number of infectious units of blood for each of these four infections using either current ELISA or the combination of RDT and PRT. RESULTS: Compared to currently used ELISA, the combination of RDTs and PRT could reduce the rate of infectious units by 100, 20, 98, and 83% for HIV, HBV, HCV, and malaria, respectively, and would prevent use of 758 units of infectious blood per 10,000 units transfused. CONCLUSION: The combination of RDTs and PRT may improve blood safety in low-resource areas.

Selective tumor cell death induced by irradiated riboflavin through recognizing DNA G-T mismatch.

Riboflavin (vitamin B2) has been thought to be a promising antitumoral agent in photodynamic therapy, though the further application of the method was limited by the unclear molecular mechanism. Our work reveals that riboflavin was able to recognize G-T mismatch specifically and induce single-strand breaks in duplex DNA targets efficiently under irradiation. In the presence of riboflavin, the photo-irradiation could induce the death of tumor cells that are defective in mismatch repair system selectively, highlighting the G-T mismatch as potential drug target for tumor cells. Moreover, riboflavin is a promising leading compound for further drug design due to its inherent specific recognition of the G-T mismatch.

Chondrogenically primed tonsil-derived mesenchymal stem cells encapsulated in riboflavin-induced photocrosslinking collagen-hyaluronic acid hydrogel for meniscus tissue repairs.

Current meniscus tissue repairing strategies involve partial or total meniscectomy, followed by allograft transplantation or synthetic material implantation. However, allografts and synthetic implants have major drawbacks such as the limited supply of grafts and lack of integration into host tissue, respectively. In this study, we investigated the effects of conditioned medium (CM) from meniscal fibrochondrocytes and TGF-ß3 on tonsil-derived mesenchymal stem cells (T-MSCs) for meniscus tissue engineering. CM-expanded T-MSCs were encapsulated in riboflavin-induced photocrosslinked collagen-hyaluronic acid (COL-RF-HA) hydrogels and cultured in chondrogenic medium containing TGF-ß3. In vitro results indicate that CM-expanded cells followed by TGF-ß3 exposure stimulated the expression of fibrocartilage-related genes (COL2, SOX9, ACAN, COL1) and production of extracellular matrix components. Histological assessment of in vitro and subcutaneously implanted in vivo constructs demonstrated that CM-expanded cells followed by TGF-ß3 exposure resulted in highest cell proliferation, GAG accumulation, and collagen deposition. Furthermore, when implanted into meniscus defect model, CM treatment amplified the potential of TGF-ß3 and induced complete regeneration. STATEMENT OF SIGNIFICANCE: Conditioned medium derived from chondrocytes have been reported to effectively prime mesenchymal stem cells toward chondrogenic lineage. Type I collagen is the main component of meniscus extracellular matrix and hyaluronic acid is known to promote meniscus regeneration. In this manuscript, we investigated the effects of conditioned medium (CM) and transforming growth factor-ß3 (TGF-ß3) on tonsil-derived mesenchymal stem cells (T-MSCs) encapsulated in riboflavin-induced photocrosslinked collagen-hyaluronic acid (COL-RF-HA) hydrogel. We employed a novel source of conditioned medium, derived from meniscal fibrochondrocytes. Our in vitro and in vivo results collectively illustrate that CM-expanded cells followed by TGF-ß3 exposure have the best potential for meniscus regeneration. This manuscript highlights a novel stem cell commitment strategy combined with biomaterials designs for meniscus regeneration.

Modeling and Elucidation of the Kinetics of Multiple Consecutive Photoreactions AB4(4Φ) With Φ-order Kinetics. Application to the Photodegradation of Riboflavin.

New semi-empirical rate-law system of equations is proposed for the first time for consecutive photoreactions that involve up to 4 photoreaction steps, AB4(4Φ). The equation system was developed, tested, and validated against synthetic kinetic traces generated by fifth-order Runge-Kutta calculations. The model accurately fitted the kinetic traces of Riboflavin photodegradation in ethanol which decomposes via the AB2(2Φ) mechanism involving 2 consecutive photoreaction steps. A kinetic elucidation methodology useful for consecutive photoreactions was also proposed to determine all the kinetic parameters and reaction attributes defining AB2(2Φ) reactions. The quantum yields of photodegradation, determined for wavelengths in the visible region 400-480 nm, ranged from 0.005 to 0.00756 and 0.0012 to 8 10-5 for the first and second photoreaction steps, respectively. They were found to increase with wavelength in defined sigmoid functions. For this monochromatic irradiation range, riboflavin proved to be a useful actinometer. Finally, a photodegradation scale based on pseudo-rate-constant values was also proposed for drugs. This scale (including 4 groups) is thought to contribute to rationalizing photodegradation testing and might prove useful in categorizing drugs' photodegradation reactivity.

Sequence-specific RNA Photocleavage by Single-stranded DNA in Presence of Riboflavin.

Constant efforts have been made to develop new method to realize sequence-specific RNA degradation, which could cause inhibition of the expression of targeted gene. Herein, by using an unmodified short DNA oligonucleotide for sequence recognition and endogenic small molecule, vitamin B2 (riboflavin) as photosensitizer, we report a simple strategy to realize the sequence-specific photocleavage of targeted RNA. The DNA strand is complimentary to the target sequence to form DNA/RNA duplex containing a G • U wobble in the middle. The cleavage reaction goes through oxidative elimination mechanism at the nucleoside downstream of U of the G • U wobble in duplex to obtain unnatural RNA terminal, and the whole process is under tight control by using light as switch, which means the cleavage could be carried out according to specific spatial and temporal requirements. The biocompatibility of this method makes the DNA strand in combination with riboflavin a promising molecular tool for RNA manipulation.

Corneal collagen cross-linking for treating keratoconus.

BACKGROUND: Keratoconus is a condition of the eye that affects approximately 1 in 2000 people. The disease leads to a gradual increase in corneal curvature and decrease in visual acuity with consequent impact on quality of life. Collagen cross-linking (CXL) with ultraviolet A (UVA) light and riboflavin (vitamin B2) is a relatively new treatment that has been reported to slow or halt the progression of the disease in its early stages. OBJECTIVES: The objective of this review was to assess whether there is evidence that CXL is an effective and safe treatment for halting the progression of keratoconus compared to no treatment. SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL; 2014, Issue 7), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to August 2014), EMBASE (January 1980 to August 2014), Latin American and Caribbean Health Sciences Literature Database (LILACS) (1982 to August 2014), Cumulative Index to Nursing and Allied Health Literature (CINAHL) (1982 to August 2014), OpenGrey (System for Information on Grey Literature in Europe) (www.opengrey.eu/), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the World Health Organisation International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We used no date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 28 August 2014. SELECTION CRITERIA: We included randomised controlled trials (RCTs) where CXL with UVA light and riboflavin was used to treat people with keratoconus and was compared to no treatment. DATA COLLECTION AND ANALYSIS: Two review authors independently screened the search results, assessed trial quality, and extracted data using standard methodological procedures expected by Cochrane. Our primary outcomes were two indicators of progression at 12 months: increase in maximum keratometry of 1.5 dioptres (D) or more and deterioration in uncorrected visual acuity of more than 0.2 logMAR. MAIN RESULTS: We included three RCTs conducted in Australia, the United Kingdom, and the United States that enrolled a total of 225 eyes and analysed 219 eyes. The total number of people enrolled was not clear in two of the studies. Only adults were enrolled into these studies. Out of the eyes analysed, 119 had CXL (all using the epithelium-off technique) and 100 served as controls. One of these studies only reported comparative data on review outcomes. All three studies were at high risk for performance bias (lack of masking), detection bias (only one trial attempted to mask outcome assessment), and attrition bias (incomplete follow-up). It was not possible to pool data due to differences in measuring and reporting outcomes. We identified a further three unpublished trials that potentially had enrolled a total of 195 participants.There was limited evidence on the risk of progression. Analysis of the first few participants followed up to one year in one study suggested that eyes given CXL were less likely to have an increase in maximum keratometry of 1.5 D or more at 12 months compared to eyes given no treatment, but the confidence intervals (CI) were wide and compatible with no effect or more progression in the CXL group (risk ratio (RR) 0.12, 95% CI 0.01 to 2.00, 19 eyes). The same study reported the number of eyes with an increase of 2 D or more at 36 months in the whole cohort with a RR of 0.03 favouring CXL (95% CI 0.00 to 0.43, 94 eyes). Another study reported "progression" at 18 months using a different definition; people receiving CXL were less likely to progress, but again the effect was uncertain (RR 0.14, 95% CI 0.01 to 2.61, 44 eyes). We judged this to be very low-quality evidence due to the risk of bias of included studies, imprecision, indirectness and publication bias but noted that the size of the potential effect was large.On average, treated eyes had a less steep cornea (approximately 2 D less steep) (mean difference (MD) -1.92, 95% CI -2.54 to -1.30, 94 eyes, 1 RCT, very low-quality evidence) and better uncorrected visual acuity (approximately 2 lines or 10 letters better) (MD -0.20, 95% CI -0.31 to -0.09, 94 eyes, 1 RCT, very low-quality evidence) at 12 months. None of the studies reported loss of 0.2 logMAR acuity. The data on corneal thickness were inconsistent. There were no data available on quality of life or costs. Adverse effects were not uncommon but mostly transient and of low clinical significance. In one trial, 3 out of 12 participants treated with CXL had an adverse effect including corneal oedema, anterior chamber inflammation, and recurrent corneal erosions. In one trial at 3 years 3 out of 50 participants experienced adverse events including mild diffuse corneal oedema and paracentral infiltrate, peripheral corneal vascularisation, and subepithelial infiltrates and anterior chamber inflammation. No adverse effects were reported in the control groups. AUTHORS' CONCLUSIONS: The evidence for the use of CXL in the management of keratoconus is limited due the lack of properly conducted RCTs.

Solvent Effect on the Photolysis of Riboflavin.

The kinetics of photolysis of riboflavin (RF) in water (pH 7.0) and in organic solvents (acetonitrile, methanol, ethanol, 1-propanol, 1-butanol, ethyl acetate) has been studied using a multicomponent spectrometric method for the assay of RF and its major photoproducts, formylmethylflavin and lumichrome. The apparent first-order rate constants (k obs) for the reaction range from 3.19 (ethyl acetate) to 4.61 × 10(-3) min(-1) (water). The values of k obs have been found to be a linear function of solvent dielectric constant implying the participation of a dipolar intermediate along the reaction pathway. The degradation of this intermediate is promoted by the polarity of the medium. This indicates a greater stabilization of the excited-triplet states of RF with an increase in solvent polarity to facilitate its reduction. The rate constants for the reaction show a linear relation with the solvent acceptor number indicating the degree of solute-solvent interaction in different solvents. It would depend on the electron-donating capacity of RF molecule in organic solvents. The values of k obs are inversely proportional to the viscosity of the medium as a result of diffusion-controlled processes.

Photocatalytic benzylic C-H bond oxidation with a flavin scandium complex.

The enhanced reduction potential of riboflavin tetraacetate coordinating to scandium triflate enables the challenging photocatalytic C-H oxidation of electron-deficient alkylbenzenes and benzyl alcohols.

Influence of crystal modification on the photoinduced color change in riboflavin.

Two different qualities of riboflavin (RF) i.e., synthetic (RFs) and biosynthetic riboflavin (RFbs) have been investigated with respect to photoinduced color change in the solid state. Several methods (XRD, FT-IR, VIS-, NIR- and fluorescence spectroscopy) were employed to elucidate the properties of the crystalline structure of RFs and RFbs and the influence of irradiation on the color and structural changes of the samples in the solid state. It was shown that RFs an RFbs represent two different crystal modifications of riboflavin and that RFbs can easily be transformed into a dihydrate upon exposure to humidity. Based on the observed irreversible color change and reduction in fluorescence intensity upon irradiation, an irreversible photoreduction of the molecule was assumed in case of RFs. A more pronounced, reversible color change and reversible reduction in fluorescence intensity indicated a reversible photoreduction process in the case of RFbs. The mechanism of these processes was further investigated by means of NIR and FT-IR spectrophotometry. It is apparent from the current study that the crystal modification of RF can strongly influence the solid state photochemistry of this molecule.