A Reversible Mechanochromic AIEgen Based on Triphenylamine for the Selective Detection of Vitamin B2 (Riboflavin) in Aqueous Media and Histotoxicity.

(E)-Ethyl 2-cyano-3-(4'-(diphenyl amino)-[1,1'-biphenyl]-4-yl) acrylate (RSJ) is a novel luminogen based on triphenylamine. It has been fully synthesized and characterized, exhibiting an incredible photophysical phenomenon known as aggregation-induced emission (AIE). This work describes a fluorescent sensor that detects vitamin B2 in mixed aqueous media with high selectivity and a low limit of detection as well as a mechanism for reversible mechanochromic luminescence. Moreover, the molecule was validated for its nontoxicity in water using a histotoxicological study. Fish subjected to two different concentrations of the "novel luminogen" that displayed photophysical phenomena during sensing of vitamin B2 (riboflavin) in mixed aqueous media did not exhibit any significant differences in the structural makeup of their liver, kidney, gills, brain, and muscle tissues when compared with the control group.

Riboflavin (vitamin B2) sensitized photooxidation of ascorbic acid (vitamin C): A kinetic study.

Ascorbic acid (AH2) photoxidation sensitized by riboflavin (RF) has been studied between pH 2.0 and 12.0 in ambient air and anaerobic environment using UV and visible irradiation sources. The kinetics of AH2 degradation in aqueous medium along with RF is found to be first-order for its photodegradation. AH2 photolysis rate constants in aerobic and anaerobic conditions with RF (1.0-5.0 × 10-5 M) are 0.14-3.89 × 10-2 and 0.026-0.740 × 10-2 min-1, respectively. The rate constants (k2) of second-order kinetics for AH2 and RF photochemical interaction in aerobic and anaerobic conditions are in the range of 0.24-3.70 to 0.05-0.70 × 10-3 M-1 min-1, respectively, which manifests that increasing the RF concentration also increases the rate of photodegradation (photooxidation) of AH2. The k2 versus pH graph is bell-shaped which indicates that increasing the pH increases photolytic degradation rate of AH2 with RF. Increasing the pH results in the increased ionization of AH2 (ascorbyl anion, AH-) and redox potential which leads to the higher rates of photodegradation of AH2. Two-component spectrophotometric (243 and 266 nm, AH2 and RF, respectively) and high-performance liquid chromatography (HPLC) methods have been used to determine the concentration of AH2 and RF in pure and degraded solutions. The results obtained from these two methods are compared using a student t-test which showed no noteworthy difference between them.

Antioxidant activity of an Mg(II) compound containing ferulic acid as a chelator: potential application for active packaging and riboflavin stabilisation.

Foods rich in riboflavin (Rf) are susceptible to degradation due to oxidative processes with the formation of radicals. Herein, we describe the features and stability of an Mg(II) complex containing ferulic acid (fer) and 1,10-phenanthroline (phen) as chelators: henceforth called Mg(phen)(fer). The electrochemical behavior of Mg(phen)(fer) is pH dependent and results from the stabilisation of the corresponding phenoxyl radical via complexation with Mg(II). This stabilisation enhances the antioxidant activity of Mg(phen)(fer) with respect to free fer and commercial antioxidants. Mg(phen)(fer) scavenges and neutralizes DPPH˙ (IC50 = 15.6 µmol L-1), ABTS˙+ (IC50 = 5.65 µmol L-1), peroxyl radical (IC50 = 5.64 µg L-1) and 1O2 (IC50 = 0.7 µg m-1). Mg(phen)(fer) effectively protects riboflavin (Rf) against photodegradation by quenching the singlet excited states of Rf regardless of the conditions. Also, the complex Mg(phen)(fer) was effectively incorporated into starch films, broadening its applications, as shown by microbiological studies. Thus, Mg(phen)(fer) has high potential for use in Rf-rich foods and to become a new alternative to the synthetic antioxidants currently used.

Riboflavin interactions with the chicken isolated carrier protein.

Riboflavin, a member of the B vitamin family, is a water-soluble vitamin that participates in energy metabolism processes via two coenzymes, flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), in oxidized and reduced forms. Low levels of riboflavin have been associated with growth and developmental problems. In an effort to investigate the role of hydrogen bonding in the interactions between riboflavin and chicken riboflavin binding protein, the solid state geometry characteristics of a riboflavin derivative stripped of hydroxyl groups except the primary one, N-(6'-hydroxyhexyl)isoalloxazine, were investigated and found that π-stacking and hydrogen bonding involving the isoalloxazine rings are the primary intermolecular interactions. Subsequent comparative fluorescence studies showed that at neutral pH, in presence of the protein, quenching of N-(6'-hydroxyhexyl)isoalloxazine and riboflavin occurred similarly suggesting that the hydroxyl groups were not a key component of the vitamin protein interactions in the binding pocket.

Enzymes in riboflavin biosynthesis: Potential antibiotic drug targets.

The rapid resistance of pathogens to antibiotics has emerged as a major threat to global health. Identification of new antibiotic targets is thus needed for developing alternative drugs. Genes encoding enzymes involved in the biosynthesis of riboflavin and flavin cofactors (FMN/FAD) are attractive targets because these enzymatic reactions are necessary for most bacteria to synthesize flavin cofactors for use in their central metabolic reactions. Moreover, humans lack most of these enzymes because we uptake riboflavin from our diet. This review discusses the current knowledge of enzymes involved in bacterial biosynthesis of riboflavin and other flavin cofactors, as well as the functions of the FMN riboswitch. Here, we highlight recent progress in the structural and mechanistic characterization, and inhibition of GTP cyclohydrolase II (GCH II), lumazine synthase (LS), riboflavin synthase (RFS), FAD synthetase (FADS), and FMN riboswitch, which have been identified as plausible antibiotic targets. As the structures and functions of these enzymes and regulatory systems are not completely understood, they are attractive as subjects for future in-depth biochemical and biophysical analysis.

Identification and characterization of archaeal and bacterial F420 -dependent thioredoxin reductases.

The thioredoxin pathway is an antioxidant system present in most organisms. Electrons flow from a thioredoxin reductase to thioredoxin at the expense of a specific electron donor. Most known thioredoxin reductases rely on NADPH as a reducing cofactor. Yet, in 2016, a new type of thioredoxin reductase was discovered in Archaea which utilize instead a reduced deazaflavin cofactor (F420 H2 ). For this reason, the respective enzyme was named deazaflavin-dependent flavin-containing thioredoxin reductase (DFTR). To have a broader understanding of the biochemistry of DFTRs, we identified and characterized two other archaeal representatives. A detailed kinetic study, which included pre-steady state kinetic analyses, revealed that these two DFTRs are highly specific for F420 H2 while displaying marginal activity with NADPH. Nevertheless, they share mechanistic features with the canonical thioredoxin reductases that are dependent on NADPH (NTRs). A detailed structural analysis led to the identification of two key residues that tune cofactor specificity of DFTRs. This allowed us to propose a DFTR-specific sequence motif that enabled for the first time the identification and experimental characterization of a bacterial DFTR.

Mechanistic Insights into Roseoflavin Synthesis by N,N-8-Demethyl-8-aminoriboflavin Dimethyltransferase (RosA): Molecular Dynamics Simulations and Residue Conservation Analysis.

8-Demethyl-8-dimethylaminoriboflavin (Roseoflavin or RoF) is a natural riboflavin analogue found in Streptomyces davaonensis and Streptomyces cinnabarinus. RoF displays potent antibiotic properties because it affects FMN riboswitches and flavoproteins of cellular targets. N,N-8-Demethyl-8-aminoriboflavin dimethyltransferase (RosA) is an enzyme that catalyzes the last step of RoF biosynthesis, a consecutive dimethylation of 8-demethyl-8-aminoriboflavin (AF) to generate RoF. Thus, understanding mechanistic insights into RosA structures and mechanisms could lead to the improvement of the RoF product yield. Herein, mechanistic insights into roseoflavin synthesis by RosA were evaluated using molecular dynamics simulations. The obtained results revealed that RosA possibly catalyzes the reaction by positioning the substrate binding to have proper distance and orientation to the methyl group donor, S-adenosylmethionine. No direct participation of catalytic residues in the reaction was identified. The enzyme's active site structures change drastically to accommodate the ligand binding. On the basis of the MM/GBSA calculations and conservation analysis, the amino acid residues involved in substrate binding were identified. The structural information obtained from this study could be beneficial in designing RosA to efficiently produce roseoflavin.

Lumichrome from the photolytic riboflavin acts as an electron shuttle in microbial photoelectrochemical systems.

Riboflavin has been proposed to serve as an electron shuttle in photoelectrochemical systems. However, riboflavin was also observed for abiotic photolysis under illumination. Such conflicting reports raise the necessity for further investigation. In this study, riboflavin secreted by Rhodopseudomonas palustris was studied to clarify its stability and electron shuttle function under illumination. The data of high-performance liquid chromatography-mass spectrometry showed that the riboflavin was photolyzed to lumichrome in microbial photoelectrochemical systems. In addition, the anodic current increased by 75% after adding lumichrome compared with that of the control; it further demonstrated that lumichrome, not riboflavin, as an electron shuttle could facilitate microbial electron transfer. This study clarifies the mechanism of the interface process in microbial photoelectrochemical systems.

Structures of the sulfite detoxifying F420-dependent enzyme from Methanococcales.

Methanogenic archaea are main actors in the carbon cycle but are sensitive to reactive sulfite. Some methanogens use a sulfite detoxification system that combines an F420H2-oxidase with a sulfite reductase, both of which are proposed precursors of modern enzymes. Here, we present snapshots of this coupled system, named coenzyme F420-dependent sulfite reductase (Group I Fsr), obtained from two marine methanogens. Fsr organizes as a homotetramer, harboring an intertwined six-[4Fe-4S] cluster relay characterized by spectroscopy. The wire, spanning 5.4 nm, electronically connects the flavin to the siroheme center. Despite a structural architecture similar to dissimilatory sulfite reductases, Fsr shows a siroheme coordination and a reaction mechanism identical to assimilatory sulfite reductases. Accordingly, the reaction of Fsr is unidirectional, reducing sulfite or nitrite with F420H2. Our results provide structural insights into this unique fusion, in which a primitive sulfite reductase turns a poison into an elementary block of life.

Microporous Matrimid/PIM-1 Thin Film Composite Membranes with Narrow Pore Size Distribution used for Molecular Separation in Organic Solvents.

Polymers of intrinsic microporosity (PIMs) are a class of microporous organic materials that contain interconnected pores of less than 2 nm in diameter. Such materials are of great potential used in membranes for molecular separation, such as drug fractionation in pharmaceutical industry. However, the PIMs membranes are often susceptible to low separation selectivity toward different molecules due to their wide pore size distribution. Herein, a linear polyimide, Matrimid, is incorporated with PIM-1 (a typical member of PIMs) by solution blending, and the blends are dip-coated onto a polyimide P84 support membrane to prepare thin-film composite (TFC) membranes to control pore size distribution while keep high microporosity. The component miscibility, pore characteristics, and molecular separation performances of the Matrimid/PIM-1 TFC membranes are investigated in detail. The Matrimid and PIM-1 are partially miscible due to their similar Hansen solubility parameters. The Matrimid endows the selective layers (coatings) with narrower pore size distribution due to more compact chain packing. The prepared Matrimid/PIM-1 TFC membranes show high selectivity for separation of riboflavin (80% of retention) and isatin (only 5% of retention). The developed membranes exhibit great potential for separating molecules with different molecular weights.

Catalytic nanozyme Zn/Cl-doped carbon quantum dots as ratiometric fluorescent probe for sequential on-off-on detection of riboflavin, Cu2+ and thiamine.

A novel metal-doped Zn/Cl carbon quantum dots (Zn/Cl-CQDs) was developed successfully as ratiometric fluorescent probes for the sequential on-off-on detection of riboflavin, Cu2+ ion and thiamine. The excellent catalytic performance of the Zn/Cl-CQDs nanozyme serves as an ideal platform for sensitive detection of thiamine. Due to the addition of riboflavin to the Zn/Cl-CQDs, the blue emission peak of Zn/Cl-CQDs at 440 nm remains unaffected and used as an internal reference approach, while the green emission peak of riboflavin at 520 nm appeared and increased remarkably. Following the presence of Cu2+, a quenching blue fluorescence signal of Zn/Cl-CQDs was observed which resulted in consequent fluorescent 'turn-off' response toward Cu2+ ion. Finally, upon the addition of thiamine to the above solution under alkaline condition, the blue emission of Zn/Cl-CQDs was gradually recovered. The prepared Zn/Cl-CQDs could act as a nanozyme catalyst for directly catalyzing the oxidation of non-fluorescent substrate of thiamine to produce highly fluorescent substrate of thiochrome. As a result, the blue fluorescence emission peak at 440 nm was recovered. Eventually, the sequential detection properties of ratiometric probes for riboflavin, Cu2+ ion and thiamine were successfully applied in VB2 tablets, drinking water and VB1 tablet with good recoveries of 96.21%, 98.25% and 98.44%, respectively.

Impact of photosensitizers and light wavelength on photooxidation of phytosterols in soymilk emulsions.

The impact of photosensitizer and wavelength on photooxidation of phytosterols (PS) in soymilk and the oxidative stability of lipid and protein was determined. The oxidation of lipid and the consumption of dissolved oxygen showed a close relationship with PS oxidation. Riboflavin (Rb) leads to extra oxidation of both lipid and protein, and chlorophyll (Chl) prefer to absorb to and change the structure of protein. The influence of Rb and Chl on PS degradation under different wavelengths of light in the range of 365-665 nm was measured. Original soymilk emulsion placed under UVA (365-375 nm) and violet (400-410 nm) light underwent the most PS deterioration, whereas riboflavin was responsible for oxidation around blue (465-475 nm) region and extra formation of 6ß-OH sterols, and chlorophyll enriched emulsion was vulnerable under red (645-665 nm) light. The wavelength of light (UVA > violet > blue > green > red > yellow) showed a great different effect in oxidation of PS and formation of phytosterol oxidation products (POPs). The UVA, violet, blue and red light gives rise to the prior five kind oxides of phytosterol: 6α-OH, 7α-OH, 7ß-OH, 5,6ß-epoxy and 7-keto.

Evidence for the Chemical Mechanism of RibB (3,4-Dihydroxy-2-butanone 4-phosphate Synthase) of Riboflavin Biosynthesis.

RibB (3,4-dihydroxy-2-butanone 4-phosphate synthase) is a magnesium-dependent enzyme that excises the C4 of d-ribulose-5-phosphate (d-Ru5P) as formate. RibB generates the four-carbon substrate for lumazine synthase that is incorporated into the xylene moiety of lumazine and ultimately the riboflavin isoalloxazine. The reaction was first identified by Bacher and co-workers in the 1990s, and their chemical mechanism hypothesis became canonical despite minimal direct evidence. X-ray crystal structures of RibB typically show two metal ions when solved in the presence of non-native metals and/or liganding non-substrate analogues, and the consensus hypothetical mechanism has incorporated this cofactor set. We have used a variety of biochemical approaches to further characterize the chemistry catalyzed by RibB from Vibrio cholera (VcRibB). We show that full activity is achieved at metal ion concentrations equal to the enzyme concentration. This was confirmed by electron paramagnetic resonance of the enzyme reconstituted with manganese and crystal structures liganded with Mn2+ and a variety of sugar phosphates. Two transient species prior to the formation of products were identified using acid quench of single turnover reactions in combination with NMR for singly and fully 13C-labeled d-Ru5P. These data indicate that dehydration of C1 forms the first transient species, which undergoes rearrangement by a 1,2 migration, fusing C5 to C3 and generating a hydrated C4 that is poised for elimination as formate. Structures determined from time-dependent Mn2+ soaks of VcRibB-d-Ru5P crystals show accumulation in crystallo of the same intermediates. Collectively, these data reveal for the first time crucial transient chemical states in the mechanism of RibB.

Uracil-Appended Fluorescent Sensor for Cu2+ and Hg2+ Ions: Real-Life Utilities Including Recognition of Vitamin B2 (Riboflavin) in Milk Products and Invisible Ink Applications.

A simple uracil-appended fluorescent sensor (1) has been developed by one pot reaction and characterized by using common spectroscopic methods such as UV-vis, Fluorescence, HRMS and FT-IR analyses. Upon addition of various metal ions to the CH3CN solution of sensor 1, the fluorescence was quenched in the presence of Cu2+ / Hg2+ ions. The limit of detection for Cu2+ and Hg2+ was calculated to be 3.31 and 0.316 µM, respectively. Further, the sensor was applied for real-life applications in the determination of Vitamin B2 (riboflavin) and its presence in milk products. With the incorporation of different sources of vitamin-B to acetonitrile solution of it, there was discernible fluorescence enhancement only in the presence of vitamin B2. Also, it has been successfully applied for the detection of Vitamin B2 (riboflavin) in milk and curd. Moreover, based on the fluorescent color changes, the sensor was utilized for invisible ink applications.

Photoisomerization of Sulindac and Ozagrel Hydrochloride by Vitamin B2 Catalyst Under Visible Light Irradiation.

PURPOSE: Photoisomerization of the E/Z-alkene structures of drugs is a matter of concern as it could result in potency loss and adverse side effects. This study focused on light-induced isomerization of sulindac and ozagrel hydrochloride catalyzed by concomitant vitamin B2 under light-emitting diode (LED) or fluorescent light. METHODS: In the presence of 0.05/0.03 equivalents of vitamin B2/flavin adenine dinucleotide (FAD), sulindac or ozagrel hydrochloride was irradiated with LED light (405 nm) or fluorescent light. The photoisomerization in CD3OD and D2O was monitored by 1H NMR spectroscopy. RESULTS: Sulindac and ozagrel hydrochloride isomerized in the presence of a catalytic amount of vitamin B2 or FAD under irradiation of 405 nm LED light and fluorescent light. Irradiation with LED light was found to be more effective than fluorescent light irradiation. The rate of photoisomerization was affected by the solvent, and the reaction in CD3OD proceeded faster than in D2O. Furthermore, ozagrel hydrochloride was more prone to isomerization than sulindac. CONCLUSION: The catalytic activity of vitamin B2 or FAD was demonstrated in the photoisomerization reaction of sulindac and ozagrel hydrochloride. Considering that the rate of photoisomerization in D2O is very slow, the possibility of the occurrence of photoisomerization during clinical use is low. However, this study suggests that the interfusion of vitamin B2 or FAD under excessive light exposure should be avoided as a caution during intravenous administration of sulindac or ozagrel hydrochloride.

Biomimetic photooxidation of noscapine sensitized by a riboflavin derivative in water: The combined role of natural dyes and solar light in environmental remediation.

Noscapine (NSC) is a benzyl-isoquinoline alkaloid discovered in 1930 as an antitussive agent. Recently, NSC has also been reported to exhibit antitumor activity and, according to computational studies, it is able to attack the protease enzyme of Coronavirus (COVID-19) and thus could be used as antiviral for COVID-19 pandemic. Therefore, an increasing use of this drug could be envisaged in the coming years. NSC is readily metabolized with a half-life of 4.5 h giving rise to cotarnine, hydrocotarnine, and meconine, arising from the oxidative breaking of the CC bond between isoquinoline and phthalide moieties. Because of its potentially increasing use, high concentrations of NSC but also its metabolites will be delivered in the environment and potentially affect natural ecosystems. Thus, the aim of this work is to investigate the degradation of NSC in the presence of naturally occurring photocatalysts. As a matter of fact, the present contribution has demonstrated that NSC can be efficiently degraded in the presence of a derivative of the natural organic dye Riboflavin (RFTA) upon exposure to visible light. Indeed, a detailed study of the mechanism involved in the photodegradation revealed the similarities between the biomimetic and the photocatalyzed processes. In fact, the main photoproducts of NSC were identified as cotarnine and opianic acid based on a careful UPLC-MS2 analysis compared to the independently synthesized standards. The former is coincident with one of the main metabolites obtained in humans, whereas the latter is related to meconine, a second major metabolite of NSC. Photophysical experiments demonstrated that the observed oxidative cleavage is mediated mainly by singlet oxygen in a medium in which the lifetime of 1O2 is long enough, or by electron transfer to the triplet excited state of RFTA if the photodegradation occurs in aqueous media, where the 1O2 lifetime is very short.

Improved stability of liposome-stabilized emulsions as a co-encapsulation delivery system for vitamin B2, vitamin E and ß-carotene.

To realize the co-encapsulation of multiple nutraceuticals with different solubilities, Pickering emulsions stabilized by freshly-prepared liposome suspension stabilized emulsion (Fre-Lip-Sus-E) and hydrated lyophilized liposome stabilized emulsion (Hyd-Lyo-Lip-E) were prepared, in comparison with the phospholipid stabilized emulsion (Pho-E). The particle size, zeta-potential, emulsification activity (EAI), emulsion stability (ESI), morphology, environmental stability and rheological properties of the three emulsions were compared. In addition, the in vitro digestive stability and bioaccessibility of three emulsions loaded with vitamin B2, vitamin E and ß-carotene were assessed. The results showed that the Fre-Lip-Sus-E and Hyd-Lyo-Lip-E were characterized by smaller particles and higher environmental stability than the Pho-E. The slight difference between the Hyd-Lyo-Lip-E and Fre-Lip-Sus-E might be due to the partial destruction of the phospholipid bilayer during the lyophilization of lyophilized liposomes. Rheological analysis demonstrated that all emulsions had high interfacial viscosity and significant shear thinning characteristics of pseudoplastic fluids. Compared with the Pho-E, the liposome-stabilized emulsions demonstrated good environmental stability and antioxidant properties, and the Fre-Lip-Sus-E and Hyd-Lyo-Lip-E exhibited comparable stabilising effects. Higher bioaccessibility of vitamin B2 and vitamin E in the Fre-Lip-Sus-E and Hyd-Lyo-Lip-E was observed, while ß-carotene had higher bioaccessibility in Pho-E. These results provide valuable insight into the potential for designing emulsion co-encapsulation delivery systems using liposomes as stabilizers.

Riboflavin Stabilizes Abasic, Oxidized G-Quadruplex Structures.

The G-quadruplex is a noncanonical fold of DNA commonly found at telomeres and within gene promoter regions of the genome. These guanine-rich sequences are highly susceptible to damages such as base oxidation and depurination, leading to abasic sites. In the present work, we address whether a vacancy, such as an abasic site, in a G-quadruplex serves as a specific ligand recognition site. When the G-tetrad is all guanines, the vacant (abasic) site is recognized and bound by free guanine nucleobase. However, we aim to understand whether the preference for a specific ligand recognition changes with the presence of a guanine oxidation product 8-oxo-7,8-dihydroguanine (OG) adjacent to the vacancy in the tetrad. Using molecular dynamics simulation, circular dichroism, and nuclear magnetic resonance, we examined the ability for riboflavin to stabilize abasic site-containing G-quadruplex structures. Through structural and free energy binding analysis, we observe riboflavin's ability to stabilize an abasic site-containing G-quadruplex only in the presence of an adjacent OG-modified base. Further, when compared to simulation with the vacancy filled by free guanine, we observe that the free guanine nucleobase is pushed outside of the tetrad by OG to interact with other parts of the structure, including loop residues. These results support the preference of riboflavin over free guanine to fill an OG-adjacent G-quadruplex abasic vacancy.

Photodynamic Effect of Riboflavin on Chitosan Coatings and the Application in Pork Preservation.

Riboflavin (RF) was considered to be possessed of photoactivity to generate reactive oxygen species (ROS) under ultraviolet (UV) light, which is thought to be a favorable antibacterial candidate. Herein, RF was incorporated into chitosan (CS) coatings and treated under UV with different exposure times (2, 4, and 6 h) to improve the physicochemical and antibacterial properties. The results showed that the light transmittance and antibacterial performance of chitosan coatings gradually increased with the extension of the UV irradiation time. The antibacterial ability of chitosan coatings correlated with the generation of ROS: ∙OH and H2O2, which achieved 1549.08 and 95.48 µg/g, respectively, after 6 h irradiation. Furthermore, the chitosan coatings with UV irradiation also reduced the pH value, total volatile basic nitrogen (TVB-N), ΔE, and total viable counts (TVC) and improved sensory attributes of pork. In conclusion, the UV irradiated chitosan coatings could be used as an environmentally friendly antimicrobial packaging material to effectively delay the spoilage of pork, maintain its sensory quality and prolong its shelf life.

Impact of Collagen Crosslinking on Dislocated Human Shoulder Capsules-Effect on Structural and Mechanical Properties.

Classical treatments of shoulder instability are associated with recurrence. To determine whether the modification of the capsule properties may be an alternative procedure, the effect of crosslinking treatment on the structure and mechanical properties of diseased human shoulder capsules was investigated. Joint capsules harvested from patients during shoulder surgery (n = 5) were treated or not with UV and/or riboflavin (0.1%, 1.0% and 2.5%). The structure and the mechanical properties of the capsules were determined by atomic force microscopy. The effect of treatments on cell death was investigated. Collagen fibrils were well-aligned and adjacent to each other with a D-periodicity of 66.9 ± 3.2 nm and a diameter of 71.8 ± 15.4 nm in control untreated capsules. No effect of treatments was observed on the organization of the collagen fibrils nor on their intrinsic characteristics, including D-periodicity or their mean diameter. The treatments also did not induce cell death. In contrast, UV + 2.5% riboflavin induced capsule stiffness, as revealed by the increased Young's modulus values (p < 0.0001 for each patient). Our results showed that the crosslinking procedure changed the biomechanics of diseased capsules, while keeping their structural organisation unchanged at the single fibril level. The UV/riboflavin crosslinking procedure may be a promising way to preserve the functions of collagen-based tissues and tune their elasticity for clinically relevant treatments.