Riboflavin Solution Research Articles

Exogenous Riboflavin Application at Different Growth Stages Regulates Photosynthetic Accumulation and Grain Yield in Fragrant Rice

Fragrant rice has high market value and is popular among consumers because of its pleasant fragrance. Plant growth regulators and trace elements can influence the yield and physiological indices of fragrant rice. Riboflavin, a vital component of plant vitamins, plays a crucial role in plant growth and development, and it is a water-soluble vitamin that is essential for sustaining normal photosynthesis and metabolic processes. However, the effects of riboflavin on nutrient accumulation and yield formation in fragrant rice have rarely been reported. Therefore, to further increase the yield and quality of fragrant rice, this study investigated the impact of the foliar application of riboflavin at different growth stages on nutrient accumulation and yield formation in two different genotypes of fragrant rice via a pot experiment. The experimental design consisted of three treatment groups, i.e., the T0 treatment group (control), which was sprayed with water; the T1 treatment group, which was sprayed at the booting stage; and the T2 treatment group, which was sprayed at the flowering stage; in all of these groups, 20 mg·L−1 riboflavin solution was used. The results revealed that the yields of the T1 and T2 treatments increased by 6.56–7.25% and 10.52–13.80%, respectively, compared with those of T0, which was attributed mainly to the increase in 1000-grain weight and grain filling. Furthermore, foliar spraying of riboflavin significantly increased the chlorophyll content, which resulted in the increased production of more total starch, soluble sugars, and sucrose and facilitated their transportation to the seeds. Moreover, applying riboflavin directly to the leaves increased the activity levels of the sucrose synthase (SS) and sucrose phosphate synthase (SPS) enzymes. Among the three treatments, the T2 treatment had the most pronounced effect. The results revealed that the foliar application of riboflavin could increase photosynthesis and promote the production of nonstructural carbohydrates, thereby increasing the total aboveground biomass of fragrant rice by 17.00–20.91% and 21.07–72.91% under the T1 and T2 treatments, respectively. Additionally, spraying riboflavin promoted rapid increases in the weight of fragrant rice seeds. In conclusion, foliar spraying of riboflavin during the flowering stage of aromatic rice can effectively enhance photosynthetic accumulation and yield, which is a promising physiological regulation strategy and provides new theoretical guidance for high-yield cultivation practices.

A Low-Cost, Portable, Multi-Cancer Screening Device Based on a Ratio Fluorometry and Signal Correlation Technique.

The autofluorescence of erythrocyte porphyrins has emerged as a potential method for multi-cancer early detection (MCED). With this method's dependence on research-grade spectrofluorometers, significant improvements in instrumentation are necessary to translate its potential into clinical practice, as with any promising medical technology. To fill this gap, in this paper, we present an automated ratio porphyrin analyzer for cancer screening (ARPA-CS), a low-cost, portable, and automated instrument for MCED via the ratio fluorometry of porphyrins. The ARPA-CS aims to facilitate cancer screening in an inexpensive, rapid, non-invasive, and reasonably accurate manner for use in primary clinics or at point of care. To accomplish this, the ARPA-CS uses an ultraviolet-excited optical apparatus for ratio fluorometry that features two photodetectors for detection at 590 and 630 nm. Additionally, it incorporates a synchronous detector for the precision measurement of signals based on the Walsh-ordered Walsh-Hadamard transform (WHT)w and circular shift. To estimate its single-photodetector capability, we established a linear calibration curve for the ARBA-CS exceeding four orders of magnitude with a linearity of up to 0.992 and a low detection limit of 0.296 µg/mL for riboflavin. The ARPA-CS also exhibited excellent repeatability (0.21%) and stability (0.60%). Moreover, the ratio fluorometry of three serially diluted standard solutions of riboflavin yielded a ratio of 0.4, which agrees with that expected based on the known emission spectra of riboflavin. Additionally, the ratio fluorometry of the porphyrin solution yielded a ratio of 49.82, which was ascribed to the predominant concentration of protoporphyrin IX in the brown eggshells, as confirmed in several studies. This study validates this instrument for the ratio fluorometry of porphyrins as a biomarker for MCED. Nevertheless, large and well-designed clinical trials are necessary to further elaborate more on this matter.

Exploring Riboflavin Quantification in Honey via Spectrofluorimetry: A Statistical Examination of Influential Extrinsic Variables

Background: The present study is focused on the collection of honey samples from the different geographical and climatic conditions of Khyber Pakhtunkhwa and analyzing them for the determination of riboflavin. Quantification of riboflavin, being natively fluorescent, was accomplished using spectrofluorimetric method. Riboflavin has characteristic fluorescence spectra with maximum excitation at 464 nm followed by an emission peak at 525 nm. Method: The procedure followed in this work comprised the construction of a calibration curve by plotting the fluorescence intensity of a series of riboflavin solutions versus concentration. This curve was used for the quantification of riboflavin in the collected honey samples. The effect of several external factors such as the altitude of the sampling area, type of honey bee, type of flowers from which the nectar was collected, and sampling season on the concentration of riboflavin in the honey samples was statistically evaluated. Results and Discussion: It was concluded that the samples collected from lower altitudes have high concentrations (1.156±0.08 μg g-1) of riboflavin. Similarly, the samples collected in autumn were found to have a maximum average riboflavin concentration of 1.37±0.06 μg g-1, which was higher in comparison to the samples collected in other seasons of the year. Likewise, the effect of flora on the concentration of riboflavin was also investigated and it was found that honey samples collected from areas where the nectar was collected from Ziziphus contains maximum riboflavin concentration averaged at 1.383±0.1 μg g-1. Conclusion: Based on the size of the honey bees, the samples collected from hives of small honey bees were found to have a maximum riboflavin concentration of 1.176±0.07 μg g-1. This study suggests that besides the studied vitamin, the rest of the vitamins and other nutritional components may vary in the honey samples depending upon external factors. conclusion: It was concluded that the samples collected from lower altitudes have high concentration (1.156±0.08 μg g-1) of riboflavin. Similarly, the samples collected in autumn were found to have a with a maximum average riboflavin concentration of 1.37±0.06 μg g-1, which was higher in comparison to the samples collected in other seasons of the year. Likewise, the effect of flora on the concentration of riboflavin was also investigated and it was found that honey samples collected from areas where the nectar was collected from Ziziphus contains maximum riboflavin concentration averaged at 1.383±0.1 μg g-1. Based on the size of the honey bees the samples collected from hives of small honey bees were found to have maximum riboflavin concentration of 1.176±0.07 μg g-1. This study suggests that beside the studied vitamin, the rest of the vitamins and other nutritional components may vary in the honey samples depending upon external factors.

In Vivo Femtosecond Laser Machined Transepithelial Nonlinear Optical Corneal Crosslinking Compared to Ultraviolet Corneal Crosslinking.

This study assessed the safety and efficacy of transepithelial crosslinking (CXL) using femtosecond (FS) laser-machined epithelial microchannels (MCs) followed by UVA CXL compared to FS laser (NLO CXL) in rabbits. The epithelium of 36 rabbits was machined to create 2- by 25-µm MCs at 400 MCs/mm2. Eyes were treated with 1% riboflavin (Rf) solution for 30 minutes, rinsed, and then crosslinked using UVA or NLO CXL. Rabbits were monitored by epithelial staining, optical coherence tomography (OCT) imaging, and esthesiometry. After sacrifice at 2, 4, or 8 weeks, corneas were examined for collagen autofluorescence and immunohistochemistry. NLO CXL showed no epithelial damage compared to UVA CXL, which produced on average 23.89 ± 5.6 mm2 epithelial defects that healed by day 3. UVA CXL also produced loss of corneal sensitivity averaging 0.83 ± 0.24 cm force to elicit a blink response that persisted for 28 days and remained significantly lower than control or NLO CXL. OCT imaging detected the presence of a demarcation line only following UVA CXL but not NLO CXL. Even with improved transepithelial Rf penetration, UVA CXL resulted in severe epithelial damage, loss of corneal sensitivity, and delayed wound healing persisting for a month. When MCs were paired with NLO CXL, however, these issues were mostly negated. This suggests that MC NLO CXL can achieve a faster visual recovery without postoperative pain or risk of infection. UVA CXL is a successful procedure, but there is a need for a transepithelial protocol. The combination of MCs and NLO CXL is able to keep the benefits of UVA CXL without causing epithelial damage.

Permeation characteristics and cross-linking efficacy of iontophoresis-assisted riboflavin delivery for accelerated riboflavin-ultraviolet A scleral collagen cross-linking in porcine eyes

The purpose of this study is to investigate whether the iontophoresis-assisted riboflavin delivery to posterior sclera with less delivery time, can achieve the same riboflavin permeation efficiency as the passive soaking way, and its effect on the mechanical properties of posterior sclera for accelerated scleral collagen cross-linking (A-SXL). In this study, 0.1% riboflavin solution was applied into the posterior sclera of porcine eyes either by the iontophoresis-assisted or passive soaking method, with delivery time of 5, 7.5, 10, 12.5, 15, 17.5, and 20 min, respectively. The fluorescence intensity and the distribution of riboflavin concentration in the 10 μm frozen sections of the sclera were evaluated by fluorescence inverted microscope. The posterior sclera with riboflavin treatment through either the iontophoresis-assisted or the passive soaking method for different durations ranging from 5 to 20 min was treated with ultraviolet A (UVA) irradiation at an intensity of 10 mW/cm2 for 9 min. The elastic modulus was determined at the physiological strain level using the uniaxial tensile test after ASXL. The results showed that the fluorescence intensity of riboflavin increased by prolonging the delivery time in both the iontophoresis and passive soaking groups, and the permeation depth of riboflavin remained constant over 15 min. The fluorescence intensity in the iontophoresis group was significantly higher than in the passive soaking group at 12.5 min and 15 min, respectively. The elastic modulus at 12.5 min in the iontophoresis group was significantly higher than in the passive soaking group at the same delivery time and showed no significant difference compared to the passive soaking group at 20 min. In conclusion, it indicated that iontophoresis-assisted delivery could not only shorten the surgery time but also achieve similar mechanical performance to the passive soaking method in ASXL.

Customized Corneal Cross-Linking with Microneedle-Mediated Riboflavin Delivery for Keratoconus Treatment.

In this study, a novel customized corneal cross-linking (CXL) treatment is explored that utilizes microneedles (MNs) for targeted riboflavin (RF) administration prior to the CXL procedure. Unlike the conventional "one-size-fits-all" approach, this protocol offers an option for more precise and efficacious treatment. To simulate a customized corneal crosslinking technique, four distinct microneedle (MN) molds designs, including circular, semi-circular, annular and butterfly shaped, are crafted for loading an optimized RF-hyaluronic acid solution and for the subsequent fabrication of MN arrays with varying morphologies. These MNs can gently puncture the corneal epithelium while preserving the integrity of the underlying stromal layer. Following the application of these microneedles, RF solution is replenished to enhance the RF content within the stroma through the punctures created by the MNs, resulting in exceptional customized corneal cross-linking effects that are comparable to the conventional epi-off CXL protocol. Additionally, it flattened the corneal curvature within the treated zone and facilitated rapid postoperative recovery of corneal tissue. These findings suggest that the integration of customized microneedle RF delivery with corneal crosslinking technology represents a potential novel treatment modality, holding promise for the tailored treatment of corneal pathologies, and offering a more precise and efficient alternative to traditional methods.

Early findings in a randomised controlled trial on crosslinking protocols using isoosmolar and hypoosmolar riboflavin for the treatment of progressive keratoconus.

To present baseline characteristics and to present the perioperative corneal thickness during corneal crosslinking (CXL) treatment for progressive keratoconus and to describe how the addition of sterile water (SW) efficaciously can maintain the corneal thickness. The treatment efficacy will be evaluated when the 1-year follow-up is complete. A randomised clinical study using epithelium-off CXL with continuous UVA irradiation (9 mW/cm2) and two kinds of riboflavin solutions: (i) isoosmolar dextran-based riboflavin (n = 27) and (ii) hypoosmolar dextran-free riboflavin (n = 27). progressive keratoconus with an increase in maximum keratometry value (Kmax) of 1.0 dioptre (12 months) or 0.5 dioptres (6 months). Corneae thinner than 400 μm were also included. Perioperative corneal thickness and the effect of adding SW. Seventy-four per cent of the patients in the isoosmolar group and 15% in the hypoosmolar group required the addition of SW, which effectively maintained a corneal thickness of 400 μm in all cases during CXL. The addition of SW was primarily needed during the irradiation procedure and not the preoperative soaking period. Especially during the CXL irradiation phase, isoosmolar riboflavin causes a significant dehydrating effect leading to corneal thinning during CXL. The customised addition of SW is efficacious in maintaining the corneal thickness during CXL and could increase the safety of the procedure.

Effects of Different Scleral Photo-Crosslinking Modalities on Scleral Stiffness and Hydration.

The purpose of this study was to evaluate the biomechanical and hydration differences in scleral tissue after two modalities of collagen cross-linking. Scleral tissue from 40 adult white rabbit eyes was crosslinked by application of 0.1% Rose Bengal solution followed by 80 J/cm2 green light irradiation (RGX) or by application of 0.1% riboflavin solution followed by 5.4 J/cm2 ultraviolet A irradiation (UVX). Posterior scleral strips were excised from treated and untreated sclera for tensile and hydration-tensile tests. For tensile tests, the strips were subjected to uniaxial extension after excision. For hydration-tensile tests, the strips were dehydrated, rehydrated, and then tested. Young's modulus at 8% strain and swelling rate were estimated. ANOVAs were used to test treated-induced differences in scleral biomechanical and hydration properties. Photo-crosslinked sclera tissue was stiffer (Young's modulus at 8% strain: 10.7 ± 4.5 MPa, on average across treatments) than untreated scleral tissue (7.1 ± 4.0 MPa). Scleral stiffness increased 132% after RGX and 90% after UVX compared to untreated sclera. Scleral swelling rate was reduced by 11% after RGX and by 13% after UVX. The stiffness of the treated sclera was also associated with the tissue hydration level. The lower the swelling, the higher the Young's modulus of RGX (-3.8% swelling/MPa) and UVX (-3.5% swelling/MPa) treated sclera. Cross-linking with RGX and UVX impacted the stiffness and hydration of rabbit posterior sclera. The Rose Bengal with green light irradiation may be an alternative method to determine the efficacy and suitability of inducing scleral tissue stiffening in the treatment of myopia.

Study of Influence of Various Methods of Intraoperative Keratoprotection on Morphological and Functional State of Ocular Surface System in Early Period after Phacoemulsification in Senile Cataract

Purpose: to study the effect of various methods of intraoperative keratoprotection on morphological and functional state of ocularsurface system (OSS) in early period after phacoemulsification (PE) in senile cataract (SC). Patients and methods. 240 patients (240 eyes) who applied for surgical treatment of SC. Age: 65 ± 4 years. 109 men, 131 women. All patients were divided into three observation groups according to the method of intraoperative keratoprotection: 1st group — 60 patients, corneal irrigation with balanced solution; 2nd group — 60 patients, ophthalmic viscosurgical device was applied to the cornea; 3rd group: 3a subgroup — 60 patients, soft contact lens (SCL) was applied to the cornea; subgroup 3b — 60 patients, SCL impregnated with riboflavin solution was applied to the cornea. In addition to the standard ophthalmological examination, Schirmer I test, OCT-scanning were performed, and tear breakup time (TBUT) was determined. Results. Operations were performed without complications. On the 1st day after the operation, the parameters of the Schirmer I test were higher in the eyes of 1st and 2nd groups. On the 5th day after the operation, tear production decreased sharply in all eyes. On the 10th day, an increase in tear production was observed in all groups, the maximum increase — in 3b subgroup. On the 1st day after the operation, TBUT decreased in all examined eyes. The largest significant TBUT decrease was noted in 1st group, the smallest — in 3b subgroup. On 1st day, corneal epithelial thickness (CET) decreased in all eyes, the maximum decrease was detected in 1st group. On the 5th day, CET continued to decrease in all eyes, the minimum decrease occurred in the 3b subgroup. On the 10th day — a decrease in CET in all groups with minimal significant dynamics in 3b subgroup. Conclusion. The study showed that the state of OSS in the early period after PE in SC depends on the method of intraoperative keratoprotection. The most optimal method of intraoperative protection of corneal epithelium and prevention of negative morphological and functional state of OSS after PE in SC is using of SCL impregnated with riboflavin.

SYNTHESIS AND STUDY OF THE OPTICAL PROPERTIES OF THE COLLOIDAL FORM OF IRON WITH RIBOFLAVIN AND L-LYSINE

This paper presents the results of the development and study of a colloidal complex of the essential microelement iron with vitamin B2 riboflavin and the essential amino acid L-lysine. As a result, a method for obtaining a colloidal vitamin-microelement-amino acid complex has been developed, which is carried out in 2 stages. As a result of computer quantum chemical modeling, the most optimal configuration for the interaction of the components of the colloidal complex was determined. Namely, it was found that the connection of riboflavin with the iron ion occurs through oxygen at C4 and nitrogen N3, and lysine binds to the iron ion through the carboxo and amino group in α- position. The optical characteristics of the resulting compound were studied. From an analysis of the absorption spectrum of a 0.001% aqueous solution of an iron complex with riboflavin and L-lysine, the presence of 4 maxima in the spectrum with positions at 222, 265, 374 and 436 nm was established. In the spectrum, the absorption maximum at a wavelength of 436 nm corresponds to the auxochromic amino group; its hypsochromic shift by 20 nm relative to the absorption spectrum of pure riboflavin confirms the formed bond of the amino group with the iron ion in the complex molecule. The fluorescence maximum is located at a wavelength of 522 nm, which corresponds to intense green-yellow fluorescence in both a solution of pure riboflavin and a colloidal iron complex with riboflavin and L-lysine. Analysis of the histogram of the size distribution of micelles of the complex showed the presence of one phase with a size of about 96 nm, which allows us to define the resulting iron complex with riboflavin and the amino acid L-lysine as a colloidal system. For citation: Blinov A.V., Golik A.B., Rekhman Z.A., Gvozdenko A.A., Kolodkin M.A., Bakholdina T.N. Synthesis and study of the optical properties of the colloidal form of iron with riboflavin and L-lysine. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 7. P. 96-102. DOI: 10.6060/ivkkt.20246707.6999.

Evaluation of Keratoconus Patients Refractive Status Before and after Corneal Collagen Cross-linking

Background: Corneal Collagen Cross Linking (CXL) incorporated with riboflavin solution activated by UV (Ultraviolet) irradiation is a modern promising treatment protocol for keratoconus. Evaluation of the clinical effect of CXL treatment on keratoconus patients was the aim of this study. Methods: This Quasi Experimental (before-and-after) study was comprised with 50 patients, having progressive keratoconus (progression was documented by Corneal Topography), reported to Cornea Clinic, CMH Dhaka, from February 2022 to January 2023. Before and after the CXL procedure; un-corrected and best-corrected visual acuity of study population was documented using Snellen visual acuity chart. Auto-refractometry readings were also noted. Results: Among the 50 study subjects; 26 (52%) were men and 24 (48%) were female, age was 24.14 ± 5.07 (mean+SD) years and age range was 18-35 years. Mean preoperative spherical power was −1.84 ± 0.82 Diopter (D) and mean cylindrical power was −3.66 ± 0.97 D. Postoperatively, mean spherical power was found −1.15 ± 0.55 D and mean cylindrical power was −2.87 ± 0.99 D. After CXL treatment; significant vision improvement found in 15 (30%) patients (p<0.05). Conclusion: Despite strengthening the corneal stromal collagen bond and halting the keratoconus progression, CXL treatment stabilize the refractive status of keratoconus patient and also in some extent, it improves vision. Bangladesh Armed Forces Med J Vol 56 No (2) December 2023, pp 45-50

Spatial targeted delivery of riboflavin with a controlled corneal iontophoresis delivery system in theranostic-guided UV-A light photo-therapy.

Seven human donor eye globes underwent corneal cross-linking using theranostic UV-A device with accessory corneal iontophoresis system for patterned delivery of a 0.22% riboflavin solution. Theranostic-guided UV-A light illumination assessed riboflavin distribution and treated corneas at 10 mW/cm2 for 9 min with a 5.0-mm beam size. Corneal topography maps were taken at baseline and 2-h post-treatment. Analysis utilized corneal topography elevation data, with results showing controlled riboflavin delivery led to a consistent gradient, with 40% higher levels centrally (248 ± 79 μg/cm3) than peripherally (180 ± 72 μg/cm3 at ±2.5 mm from the center). Theranostic-guided UV-A light irradiation resulted in significant changes in corneal topography, with a decrease in best-fit sphere value (-0.7 ± 0.2 D; p < 0.001) and consistent downward shift in corneal elevation map (-11.7 ± 3.7 μm). The coefficient of variation was 2.5%, indicating high procedure performance in achieving significant and reliable corneal flattening.

Riboflavin based setup as an alternative method for a preliminary screening of face mask filtration efficiency

Face masks are essential in reducing the transmission of respiratory infections and bacterial filtration efficiency, a key parameter of mask performances, requires the use of Staphylococcus aureus and specialised staff. This study aims to develop a novel method for a preliminary screening of masks or materials filtration efficiency by a green, easy and rapid setup based on the use of a riboflavin solution, a safe autofluorescent biomolecule. The proposed setup is composed of a commercial aerosol generator commonly used for aerosol therapy, custom 3D printed aerosol chamber and sample holder, a filter for downstream riboflavin detection and a vacuum pump. The filtration efficiency of four different masks was assessed using the riboflavin-based setup and the bacterial filtration efficiency (BFE). The averaged filtration efficiency values, measured with both methods, were similar but were higher for the riboflavin-based setup (about 2% for all tested samples) than bacterial filtration efficiency. Considering the good correlation, the riboflavin-based setup can be considered validated as an alternative method to bacterial filtration efficiency for masks and related materials fabrics filtration efficiency screening but This study aims to develop a novel method for a preliminary screening of masks or materials filtration efficiency by a green, easy and rapid setup based on the use of a riboflavin solution, a safe autofluorescent biomolecule, but not to replace regulation approaches. The proposed setup can be easily implemented at low price, is more rapid and eco-friendly and can be performed in chemical-physical laboratories without the needing of biosafety laboratory and specialised operators.

Evaluation of visible light and natural photosensitizers against Staphylococcus epidermidis and Staphylococcus saprophyticus planktonic cells and biofilm

Antimicrobial photoinactivation (API) has shown some promise in potentially treating different nosocomial bacterial infections, however, its application on staphylococci, especially other than Staphylococcus aureus or methicillin-resistant S. aureus (MRSA) species is still limited. Although S. aureus is a well-known and important nosocomial pathogen, several other species of the genus, particularly coagulase-negative Staphylococcus (CNS) species such as Staphylococcus epidermidis and Staphylococcus saprophyticus, can also cause healthcare-associated infections and foodborne intoxications. CNS are often involved in resilient biofilm formation on medical devices and can cause infections in patients with compromised immune systems or those undergoing invasive procedures. In this study, the effects of chlorophyllin and riboflavin-mediated API on S. epidermidis and S. saprophyticus planktonic cells and biofilm are demonstrated for the first time. Based on the residual growth determination and metabolic reduction ability changes, higher inactivating efficiency of chlorophyllin-mediated API was determined against the planktonic cells of both tested species of bacteria and against S. saprophyticus biofilm. Some insights on whether aqueous solutions of riboflavin and chlorophyllin, when illuminated with optimal exciting wavelength (440 nm and 402 nm, respectively) generate O2−•, are also provided in this work.

A nanotechnology‐based solution for epi‐on corneal cross‐linking

Keratoconus (KC) is a bilateral progressive corneal ectasia resulting in irregular astigmatism and loss of visual function, in youth and children. Corneal cross‐linking (CXL) is the standard treatment to halt the progression of KC. The conventional protocol consists of removal of the corneal epithelium (epi‐off), followed by soaking of riboflavin and then irradiation with UVA light, leading to stiffening of the cornea. However, postoperative ocular adverse events related to epithelial removal, such as infectious keratitis and delayed visual recovery, have been described. Some alternative methodologies have been tested but pain, no control on corneal permeability, and high investment for set‐up acquisition are drawbacks. Accordingly, the treatment of KC is at an extremely exciting stage, and research on delivering riboflavin into the cornea without removing the epithelium is underway.To address this clinical unmet need, we developed an advanced solution consisting of nanoparticle‐modified commercial soft contact lenses. Safety conditions were determined using ex vivo porcine eyes. The efficacy of our solution on corneal epithelial permeability to riboflavin was tested using in vivo rat eyes. Our nanotechnology‐based solution allows high spatial and temporal precision control of epithelial permeability to riboflavin. We aim to validate this innovative strategy as an epithelium‐on (epi‐on) protocol for the effective treatment of KC, with obvious advantages in terms of safety, patient comfort, and recovery time. Furthermore, our strategy is compatible with current equipment and riboflavin solutions, allowing to capitalize clinicians' expertise and the resources already existing in private clinics and public health services.This project was financially supported by Foundation for Science and Technology (FCT, Portugal): Exploratory Research Project EXPL/BIA‐BQM/0042/2021, Strategic Projects UIDB/04539/2020, UIDP/04539/2020, and UID/NEU/04539/2019; and by COMPETE‐FEDER (POCI‐01‐0145‐FEDER‐007440).

Биоптический подход к эксимерлазерной хирургии при сочетанной патологии роговицы и хрусталика

Purpose. To consider a biooptical approach to excimer laser surgery for combined pathology of the cornea and lens. Material and methods. The work is based on 20-year clinical observations of the results of excimer laser refractive, opto-reconstructive and medical surgery in combined pathology of the cornea and lens based on a biooptical approach (more than 1500 operations). Particular emphasis was placed on the cycloplegic functional test and the use of stromal saturation with 0.25% chilled to +5–7 °C isotonic riboflavin solution during photoablation. The studies used modern diagnostic devices OPD-scan, RTVue XR100 and TMS-5 and excimer ophthalmic lasers from various companies. Results. In case of combined refractive pathology of the cornea and lens, the cycloplegic test made it possible to more accurately determine the degree of ametropia, its accommodative component with compensation of corneal astigmatism, and the presence of lens astigmatism. In all cases, the determination of the volume of photorefractive ablation was calculated taking into account the contribution of the cornea and lens to the formation of ametropia and aberrations of the optical system of the eye. The diameter of the optical and transition zone during photorefractive ablation was calculated depending on the state of the pupil diameter in photopic and mesopic conditions. Obtained in the course of studies on the OPD-Scan device, objective information on the difference between the pupil width in mesopic and photopic conditions made it possible to individualize the sizes of the optical and transition zones during photorefractive ablation, to avoid the «Halo» and «Gler» effects. Photoablation with saturation of tecorneal stroma with riboflavin reduced the response of aseptic inflammatory and regenerative reactions, the severity and duration of the corneal syndrome, and provided earlier stabilization of optical refractive indices. Conclusion. When performing excimer laser refractive, opto-reconstructive and therapeutic operations with combined pathology of the cornea and lens, a biooptical approach is required, taking into account the leading role of the cornea and lens in the formation of the optical system of the eye and visual acuity. Keywords: biooptics, photoablation, excimer laser corneal surgery

Collagen changes in rabbit conjunctiva after conjunctival crosslinking.

This study aims to determine the ultrastructural changes in collagen fibrils in rabbit conjunctiva after conjunctival crosslinking using riboflavin and ultraviolet A (UVA) light at an irradiation intensity of 45 mW/cm2. Conjunctival crosslinking may increase conjunctival stiffness. The supertemporal quadrants of the right eyes of 24 adult rabbits were treated with a topical riboflavin solution (0.25%) before irradiation with UVA light at 45 mW/cm2 for 4 min. After 3 weeks, the collagen fibrils in fibril bundles were examined by electron microscopy. Immunohistochemical staining was used to detect the expression levels of collagen I and collagen III in the rabbits' conjunctiva. The diameter of the collagen fibrils in the fibril bundles varied slightly, ranging from 30 to 60 nm in the conjunctival stroma of the control group. In the treatment group, the diameter of collagen fibrils ranged from 60 to 90 nm. The thickest collagen fibrils were observed in the treatment group (up to 90 nm in diameter). In contrast, those in the conjunctival stroma of the control group were considerably smaller (up to 60 nm in diameter). However, thicknesses of collagen fibrils displayed a unimodal distribution. Both collagen I and collagen III increased after treatment with riboflavin and UVA light irradiation at 45 mW/cm2. The data indicate that in rabbits, conjunctival crosslinking with riboflavin and UVA light at 45 mW/cm2 for 4 min is safe and does not induce ultrastructural alterations of the conjunctival cells. The conjunctival crosslinking with riboflavin and UVA light at 45 mW/cm2 can increase the diameter of collagen fibrils, but the average densities of collagen I and collagen III have no statistical significance.

Comparison of topographic outcomes between HPMC based and vitamin E TPGS based riboflavin solutions after corneal cross-linking.

To compare the visual and topographic results between patients who underwent epithelium-off cross-linking using riboflavin solutions compounds hydroxypropyl methylcellulose (HPMC) 1.1% and D-alpha-tocopheryl polyethylene-glycol 1000 succinate (VE-TPGS). In this study, 37 eyes treated with HPMC and 29 eyes treated with VE-TPGS were evaluated retrospectively. Spherical equivalent (SE), refractive cylinder, corrected distance visual acuity tests (CDVA), corneal topography indices (flat and steep meridians' keratometry (K1 and K2)), maximum keratometry (K max), central, thinnest, and apical corneal thicknesses, the front and back keratoconus vertex index (KVf, KVb), and the surface asymmetry index of the front and back surface (SIf, SIb), and endothelial cell density were compared at baseline and postoperative follow-up visits (1, 3, 6, and 12months). At the end of the 12th-month, K1, K2, and Kmax were decreased in both groups. In comparison to baseline, there was a decline in the HPMC group in the 3rd- month Kmax change, an increase was observed in the VE-TPGS group. In the 12th-month KVb change, an increase was observed in the HPMC group compared to the baseline, while a decrease was observed in the VE-TPGS group. The other parameters did not show a statistically significant difference between the groups (p > 0.05). At the end of 12 months, both riboflavins were effective in stopping the progression of keratoconus and were safe for endothelium. Although both riboflavins provide a decrease in keratometry values, it can be said that VE-TPGS is superior to HPMC in correcting the ectasia on the posterior corneal surface.

Analysis of Biomechanical Response After Corneal Crosslinking with Different Fluence Levels in Porcine Corneas

Purpose To evaluate corneal stiffening of porcine corneas induced by corneal crosslinking (CXL) with constant irradiance as a function of total fluence. Methods Ninety corneas from freshly enucleated porcine eyes were divided into five groups of 18 eyes. Groups 1–4 underwent epi-off CXL using a dextran-based riboflavin solution and an irradiance of 18 mW/cm2, group 5 served as the control group. Groups 1 to 4 were treated with a total fluence of 20, 15, 10.8, and 5.4 J/cm2, respectively. Thereafter, biomechanical measurements were performed on 5 mm wide and 6 mm long strips using an uniaxial material tester. Pachymetry measurements were performed on each cornea. Results At 10% strain, the stress was 76, 56, 52, and 31% higher in groups 1–4, respectively compared to the control group. The Young’s modulus was 2.85 MPa for group 1, 2.53 MPa for group 2, 2.46 MPa for group 3, 2.12 MPa for group 4, and 1.62 MPa for the control group. The difference between groups 1 to 4 and the control group 5 were statistically significant (p = <0.001; p = <0.001; p = <0.001; p = 0.021). In addition, group 1 showed significantly more stiffening than group 4 (p = <0.001), no other significant differences were found. Pachymetry measurements revealed no statistically significant differences among the five groups. Conclusion Additional mechanical stiffening can be achieved by increasing the fluence of the CXL. There was no threshold detected up to 20 J/cm2. A higher fluence could compensate the weaker effect of accelerated or epi-on CXL procedures.

Novel use of riboflavin as a fluorescent tracer in the dissemination of aerosol and splatter in an open operatory dental clinic.

The rapid spread of severe acute respiratory syndrome coronavirus 2 and the ensuing rise of the COVID-19 pandemic have impacted healthcare unprecedentedly. With the scarcity of available resources, including healthcare providers themselves, novel methods for tracking aerosol and splatter in real time are required to alleviate demand and increase safety. This study evaluates the utility of riboflavin (vitamin B2 ) as a tracer for splatter/aerosol distribution from ultrasonic scaling in an open operatory clinic. In two experimental designs, ultrasonic scaling was performed on 18 volunteers or simulated on a manikin. Riboflavin was introduced into the irrigation system, and aerosol and splatter dissemination were evaluated for both experimental designs. Ultrasonic scaling utilizing riboflavin solution, in volunteers and manikins, leads to observable particle fluorescence under UV light. Contamination distribution varied across the different suction methods and between the volunteer and manikin trials. Nearly all observed incidences of contamination occurred within the operatory in use. Riboflavin can be used with minimal risk during dental procedures and allows for the detection of droplet spread in clinical settings in real time.