Generation of Broad Protection against Influenza with Di-Tyrosine-Cross-Linked M2e Nanoclusters.

Tyrosine cross-linking has recently been used to produce nanoclusters (NCs) from peptides to enhance their immunogenicity. In this study, NCs were generated using the ectodomain of the ion channel Matrix 2 (M2e) protein, a conserved influenza surface antigen. The NCs were administered via intranasal (IN) or intramuscular (IM) routes in a mouse model in a prime-boost regimen in the presence of the adjuvant CpG. After boost, a significant increase in anti-M2e IgG and its subtypes was observed in the serum and lungs of mice vaccinated through the IM and IN routes; however, significant enhancement in anti-M2e IgA in lungs was observed only in the IN group. Analysis of cytokine concentrations in stimulated splenocyte cultures indicated a Th1/Th17-biased response. Mice were challenged with a lethal dose of A/California/07/2009 (H1N1pdm), A/Puerto Rico/08/1934 (H1N1), or A/Hong Kong/08/1968 (H3N2) strains. Mice that received M2e NCs + CpG were significantly protected against these strains and showed decreased lung viral titers compared with the naive mice and M2e NC-alone groups. The IN-vaccinated group showed superior protection against the H3N2 strain as compared to the IM group. This research extends our earlier efforts involving the tyrosine-based cross-linking method and highlights the potential of this technology in enhancing the immunogenicity of short peptide immunogens.

Novel films of pectin extracted from ambarella fruit peel and jackfruit seed slimy sheath: Effect of ionic crosslinking on the properties of pectin film.

Here, we prepared ionically crosslinked films using pectin extracted from agro-wastes, specifically ambarella peels (AFP) and jackfruit seed slimy sheath (JFS). Physiochemical properties of pectins, including moisture content, molecular weight (Mw), degree of esterification (DE), and galacturonic acid (GA), were analyzed. Optimal extraction was determined, i.e., citric acid concentration 0.3 M, time 60 min, solid/liquid ratio 1:25, and temperature 90 °C for AFP or 85 °C for JFS. Pectin yields under these conditions were 29.67 % ± 0.35 % and 29.93 ± 0.49 %, respectively. AFP pectin revealed Mw, DE, and GA values of 533.20 kDa, 67.08 % ± 0.68 %, and 75.39 ± 0.82 %, while JFS pectin exhibited values of 859.94 kDa, 63.04 % ± 0.47 %, and 78.63 % ± 0.71 %, respectively. The pectin films crosslinked with Ca2+, Cu2+, Fe3+, or Zn2+ exhibited enhanced tensile strength and Young's modulus, along with reduced elongation at break, moisture content, water solubility, water vapor permeability, and oxygen permeability. Structural analyses indicated metal ions were effectively crosslinked with carboxyl groups of pectin. Notably, the Cu2+-crosslinked film demonstrated superior water resistance, mechanical properties, and exhibited the highest antioxidant and antibacterial activities among all tested films. Therefore, the pectin films represent a promising avenue to produce eco-friendly food packaging materials with excellent properties.

Immobilized microalgae: principles, processes and its applications in wastewater treatment.

Microalgae have emerged as potential candidates for biomass production and pollutant removal. However, expensive biomass harvesting, insufficient biomass productivity, and low energy intensity limit the large-scale production of microalgae. To break through these bottlenecks, a novel technology of immobilized microalgae culture coupled with wastewater treatment has received increasing attention in recent years. In this review, the characteristics of two immobilized microalgae culture technologies are first presented and then their mechanisms are discussed in terms of biofilm formation theories, including thermodynamic theory, Derjaguin-Landau-Verwei-Overbeek theory (DLVO) and its extended theory (xDLVO), as well as ionic cross-linking mechanisms in the process of microalgae encapsulated in alginate. The main factors (algal strains, carriers, and culture conditions) affecting the growth of microalgae are also discussed. It is also summarized that immobilized microalgae show considerable potential for nitrogen and phosphorus removal, heavy metal removal, pesticide and antibiotic removal in wastewater treatment. The role of bacteria in the cultivation of microalgae by immobilization techniques and their application in wastewater treatment are clarified. This is economically feasible and technically superior. The problems and challenges faced by immobilized microalgae are finally presented.

Development and characterization of films from Campomanesia xanthocarpa and commercial citrus pectins with different degrees of methyl-esterification.

In this study, pectins from commercial citrus and isolated from gabiroba (Campomanesia xanthocarpa) fruits, were obtained with different degrees of methyl-esterification (DM) and applied in the films. The DM ranged from 0 % to 62.5 % and the gradual de-esterification process was confirmed by mono-dimensional analysis (1H NMR). In order to investigate the influence of DM values in pectin film properties, PCP (DM: 62.5 %); PCP-5 (DM: 37.4 %); PCP-15 (DM: 19.1 %), and a fully de-esterified sample PCP-35 (DM: 0 %) were selected. The functional properties of the films clearly showed that the DM and cross-linking process are necessary to obtain a material with water resistance. Furthermore, pectin isolated from the fruits of gabiroba was purified (GW-Na, DM: 51.9 %) and partially de-esterified (GW-Na-5, DM: 37.1 %). These pectins were used, for the first time, in development of films and the physical and mechanical properties were compared with films made with PCP and PCP-5 samples. GW-Na and GW-Na-5 films presented suitable properties, with reduced solubility reduced (57.1 and 26.2 %), high degree of swelling (2.14 and 2.26), low flexibility (18.05 and 6.11 MPa), respectively. High strength and rigidity (99.36 and 1040.9 MPa), for both films (GW-Na and GW-Na-5) were demonstrated, similar to that obtained by analyzed citrus pectin.

Modulating in vitro fecal fermentation behavior of sodium alginate by Ca2+ cross-linking.

Slow fermentable dietary fibers can be utilized by human gut microbiota in the distal region of the colon and thus exert a sufficient short-chain fatty acids (SCFAs) supplement in the distal region of the human colon. Alginate (Alg) based microgels are widely fabricated and used to control their digestion by digestive enzymes releasing active substances site-specifically. Herein, sodium alginate microgels with gradient calcium-ion (Ca2+) cross-linking densities were developed, restricting their degradation by gut microbiota. Alg microgels were prepared using high-speed shearing after Alg was cross-linked with 10, 40, and 60 mmol/L Ca2+, respectively (named 10-Alg, 40-Alg, and 60-Alg). The fluorescence and atomic force microscopic results showed that the 40-Alg particle has the densest structure among the three cross-linked Alg. In vitro human fecal fermentation results revealed that the Ca2+ cross-linking exerted more restricting effects than delaying effects on the fermentation of Alg, and the 40-Alg exhibited the slowest fermentation rate and the least fermentation extent, by characterizing the residual total carbohydrate content, residual monosaccharide content, pH, and total short-chain fatty acids. The 16S rRNA gene sequencing results indicated that cross-linking structures shaped a high specifical Bacteroides-type microbial community and that OTU205 (Bacteroides_xylanisolvens) highly correlated to the cross-linking density (R = 0.65, p = 0.047). In sum, Ca2+ cross-linking generated a dense and compact structure of sodium alginate that facilitated a more restricted fermentation property and specificity-targeting microbial community structure in comparison to the original sodium alginate.

Cross-Linking Characteristics, Morphology, Dynamics, and Mechanical and Thermal Properties of Polychloroprene/Polybutadiene/Nano-Zinc (CR/BR/nZn) Compositions with Reduced Fire Hazard.

The properties of unconventional blends of crystallizable and thermo-cross-linkable polychloroprene (CR) with polybutadiene (BR) were investigated in this study. The compositions were prepared using the method of reactive processing and cross-linking in the presence of nano-sized zinc (nZn). The purpose of the research was to assess the efficacy of nano-zinc as a curing agent of polychloroprene and polybutadiene (CR/BR) composites and to obtain rubber goods characterized by increased flame resistance. The blends were filled with nano-silica (aerosil) and fillers of natural origin (chalcedonite or silitin). The cross-linking process was characterized by determining the kinetics curves, the equilibrium swelling, and the Mooney-Rivlin elasticity constants. The morphology of the vulcanizate surface was specified by scanning electron microscopy (SEM). The dynamic and mechanical properties, flammability, and toxicity of gaseous substances involved in thermal decomposition were determined. Mass changes and thermal effects were studied using simultaneous thermal analysis (STA). It was confirmed that nano-zinc is an efficient curing agent for the polychloroprene and polybutadiene compositions, with a satisfactory degree of cross-linking (αc = 0.10, CRI = 4.11 min-1), good mechanical strength (TSb = 5 MPa), satisfactory tear resistance (Ts = 2.9 N/mm), and very high flame resistance (OI = 30%, HRRmax = 283 kW/m2). Filled products could be used as non-combustible materials, confirming the low fire hazard (1/tflashover = 3.5-6.4 kW/m2∙s). The most effective filler of the tested composites was nano-sized silica.

Accelerated high fluence photoactivated chromophore for infectious keratitis-corneal cross-linking (PACK-CXL) at the slit lamp: a pilot study.

Introduction: Photoactivated Chromophore for Infectious Keratitis-Corneal Cross-Linking (PACK-CXL) has garnered substantial interest among researchers and ophthalmologists due to its high promise as a potential treatment for infectious keratitis. The aim of this study is to evaluate the efficacy and safety of high fluence PACK-CXL, using 10.0 J/cm2 (30 mW/cm2, 5 min, and 33 s) at the slit lamp. Methods: This prospective interventional, nonrandomized cohort study included 20 eyes of 20 patients with bacterial, fungal, or mixed origin keratitis who underwent high fluence PACK-CXL treatment as an adjunct therapy to conventional antimicrobial therapy per American Academy of Ophthalmology treatment guidelines. The re-epithelization time was recorded, and corneal endothelial cell density was counted before and after treatment. Results: The average re-epithelization time was 8.2 ± 2.8 days (range 3-14 days). After PACK-CXL treatment, eight patients (40%) were directly discharged, while the remained patients stayed in the hospital for an average of 5.6 ± 3.5 days. No eyes required keratoplasty. Endothelial cell density counts before and after the PACK-CXL procedure were 2,562.1 ± 397.3, and 2,564.8 ± 404.5 cells/mm2, respectively (p = 0.96). Conclusion: although it was not a randomized control trial, we conclude that high fluence PACK-CXL as an adjuvant therapy is safe with no complications observed, and efficient as time to re-epithelization was less than 14 days for all patients and no patients underwent tectonic keratoplasties. Further research is needed to compare it to the current standard of care.

Facile fabrication of Artemisia sphaerocephala krasch gum hydrogels by radiation induced cross-linking polymerization and enhanced ultrahigh adsorption for methylene blue.

Although Artemisia sphaerocephala krasch gum (ASKG) has attracted growing attention in the field of medical engineering and food industries, however, there are few studies on the gelation of ASKG. In this paper, acrylic acid modified ASKG hydrogels were prepared by radiation induced grafting, cross-linking and polymerization technique for the first time. The semi-IPN structure was prepared by the cross-linked ASKG network and poly-AAc dispersed within the network. The effects of the adsorbed dose on the swelling ratio and gel fraction were investigated. The different acrylic acid content modified ASKG hydrogels (ASKGAAc1 and ASKGAAc2) for methyl blue (MB) adsorption were investigated, and the ASKG hydrogels was also studied for comparison. The influence of pH, contact time, initial concentration, temperature, ion strength on MB adsorption were tested. The results showed that acrylic acid can promote the formation of hydrogel and greatly enhanced the adsorption of ASKG. The adsorption isotherms were well obeyed the Langmuir model, and the maximum adsorption capacity for MB of ASKG, ASKGAAc1 and ASKGAAc2 were 571.43, 1517.8 and 1654.9 mg/g, respectively. Moreover, the MB adsorption by ASKG based hydrogels was exothermic, spontaneous, and more favorable at lower temperature. Furthermore, the adsorption-desorption experiments demonstrated a good reusability of these hydrogels.

Biomacromolecule assembly of soy glycinin-potato starch complexes: Focus on structure, function, and applications.

The effect of the cross-linking mechanism and functional properties of soy glycinin (11S)-potato starch (PS) complexes was investigated in this study. The results showed that the binding effecting and spatial network structure of 11S-PS complexes via heated-induced cross-linking were adjusted by biopolymer ratios. In particular, 11S-PS complexes with the biopolymer ratios of 2:15, had a strongest intermolecular interaction through hydrogen bonds and hydrophobic force. Moreover, 11S-PS complexes at the biopolymer ratios of 2:15 exhibited a finer three-dimensional network structure, which was used as film-forming solution to enhance the barrier performance and mitigate the exposure to the environment. In addition, the 11S-PS complexes coating was effective in moderating the loss of nutrients, thereby extending their storage life in truss tomato preservation experiments. This study provides helpful to insights into the cross-linking mechanism of the 11S-PS complexes and the potential application of food-grade biopolymer composite coatings in food preservation.

Calcification of Various Bioprosthetic Materials in Rats: Is It Really Different?

The causes of heart valve bioprosthetic calcification are still not clear. In this paper, we compared the calcification in the porcine aorta (Ao) and the bovine jugular vein (Ve) walls, as well as the bovine pericardium (Pe). Biomaterials were crosslinked with glutaraldehyde (GA) and diepoxide (DE), after which they were implanted subcutaneously in young rats for 10, 20, and 30 days. Collagen, elastin, and fibrillin were visualized in non-implanted samples. Atomic absorption spectroscopy, histological methods, scanning electron microscopy, and Fourier-transform infrared spectroscopy were used to study the dynamics of calcification. By the 30th day, calcium accumulated most intensively in the collagen fibers of the GA-Pe. In elastin-rich materials, calcium deposits were associated with elastin fibers and localized differences in the walls of Ao and Ve. The DE-Pe did not calcify at all for 30 days. Alkaline phosphatase does not affect calcification since it was not found in the implant tissue. Fibrillin surrounds elastin fibers in the Ao and Ve, but its involvement in calcification is questionable. In the subcutaneous space of young rats, which are used to model the implants' calcification, the content of phosphorus was five times higher than in aging animals. We hypothesize that the centers of calcium phosphate nucleation are the positively charged nitrogen of the pyridinium rings, which is the main one in fresh elastin and appears in collagen as a result of GA preservation. Nucleation can be significantly accelerated at high concentrations of phosphorus in biological fluids. The hypothesis needs further experimental confirmation.

A tyrosine, histidine-selective bifunctional cross-linker for protein structure analysis.

Chemical cross-linking mass spectrometry (XL-MS) significantly contributes to the analysis of protein structures and the elucidation of protein-protein interactions. Currently available cross-linkers mainly target N-terminus, lysine, glutamate, aspartate, and cysteine residues in protein. Herein, a bifunctional cross-linker, named [4,4'-(disulfanediylbis(ethane-2,1-diyl)) bis(1-methyl-1,2,4-triazolidine-3,5-dione)] (DBMT) has been designed and characterized aiming to extremely expand the application of XL-MS approach. DBMT is capable of selectively targeting tyrosine residue in protein via an electrochemical click reaction, and/or targeting histidine residue in protein in the presence of 1O2 generated under photocatalytic reaction. A novel cross-linking strategy based on this cross-linker has been developed and demonstrated using model proteins, which provides a complementary XL-MS tool analyzing protein structure, protein complexes, protein-protein interactions, and even protein dynamics.

In Situ Transformable Nanoplatforms with Supramolecular Cross-Linking Triggered Complementary Function for Enhanced Cancer Photodynamic Therapy.

In vivo cross-linking of nanoparticles is widely used to increase accumulation of therapeutic agents at tumor site for enhanced therapy. However, the components in nanoplatforms usually only play for one role and are independent of each other, unable to amplify their biofunctions. Herein, a complementary functioning tumor microenvironment triggered, supramolecular coordination-induced nanoparticle cross-linking strategy is constructed for enhanced photodynamic therapy. Manganese oxide (MnOx ) and polyhydroxy photosensitizer hypericin (Hyp) are coated and loaded onto lanthanide-doped upconversion nanoparticles (UCNPs) to form transformable UCNP@MnOx -Hyp. In CT26 mouse colon cancer cells and xenograft tumors, UCNP@MnOx -Hyp is reduced by glutathione and H2 O2 , releasing Mn2+ and Hyp for in situ cross-linking to transform to UCNP@Mn2+ -Hyp. Compared to the simple photosensitizer-loaded UCNP@PEI-Hyp, the Mn2+ -Hyp coordination redshifts absorbance of Hyp and improves the energy transfer efficiency from UCNPs to Hyp (5.6-fold). In turn, the supramolecular coordination-induced UCNPs cross-linking exhibits enhanced luminescence recovery and increased intracellular accumulation of both UCNPs and Hyp, thus enhancing the photodynamic therapy efficacy both at cellular level (2.1-fold) and in vivo, realizing the function amplification of each component after responsive transformation and offering a new avenue for enhanced cancer therapy.

Insights into heat-induced molecular-level interactions between wheat and common buckwheat proteins.

This study investigated the heat-induced interactions between wheat and buckwheat proteins by heating wheat proteins, buckwheat albumin, globulin, and mixtures of wheat flour with buckwheat albumin/globulin at 50, 65, 80, 95, and 100 °C. The results showed that the cross-linking reactions of wheat glutenin with buckwheat albumin and globulin initiated at 80 and 95 °C, respectively. Buckwheat albumin decreased the extractability of α-gliadin by 35 % at 95 °C and 5.9 % at 100 °C. The linkage of buckwheat globulin to wheat glutelin prevented part of the wheat gliadin from linking to glutelin, resulting in the extractability of α- and γ-gliadin increased by 8.6 % and 11 % at 95 °C, respectively. The chemical forces results indicated that interactions between wheat and buckwheat proteins were primarily driven by disulfide bonds and hydrophobic interactions. This study provides a theoretical basis for better regulating the wheat-buckwheat protein network to improve the quality of buckwheat-enriched products.

Entirely S-protected thiolated hydroxyethylcellulose: Design of a dual cross-linking approach for hydrogels.

AIM: The aim of this study was the synthesis and evaluation of entirely S-protected thiolated hydroxyethylcellulose (HEC) with low and high viscosity, as well as thiolated poly-L-lysine (poly-L-Lys) used as dual-acting ionic as well as thiol-disulfide exchange mediated cross-linking hydrogel. METHODS: Bis(mercaptosuccinic acid) was covalently attached to low and high viscous HECs via Fisher esterification, obtaining S-protected polymers. Poly-L-Lys-cysteine was synthesized via amidation of poly-L-Lys-HBr with cysteine (Cys). Thiolated polymers were examined in terms of cytotoxicity and rheological behavior of hydrogels containing these thiomers was evaluated with a cone-plate rheometer. RESULTS: Thiomers showed less cytotoxicity compared to the corresponding unmodified polymers. Rheological studies showed that cross-linking occurred between the two polymers via thiol-disulfide exchange reactions facilitated by the complementary charges. Employing poly-L-Lys-Cys in a concentration of either 0.5 or 5% (m/v) resulted in a 34.5-fold or 17.3-fold as well as a 53.6-fold or 29.6-fold improvement in dynamic viscosity within 5 min at 37 °C on S-protected thiolated low and high viscous HEC, compared to the corresponding unmodified HECs, respectively. CONCLUSION: By the combination of anionic S-protected thiolated polymers with a cationic thiolated polymer, dual-acting hydrogels exhibiting a time dependent increase in viscosity can be designed.

Effect of Transglutaminase Post-Treatment on the Stability and Swelling Behavior of Casein Micro-Particles.

Casein microparticles are produced by flocculation of casein micelles due to volume exclusion of pectin and subsequent stabilization by film drying. Transglutaminase post-treatment alters their stability, swelling behavior, and internal structure. Untreated particles sediment due to their size and disintegrate completely after the addition of sodium dodecyl sulfate. The fact that transglutaminase-treated microparticles only sediment at comparable rates under these conditions shows that their structural integrity is not lost due to the detergent. Transglutaminase-treated particles reach an equilibrium final size after swelling instead of decomposing completely. By choosing long treatment times, swelling can also be completely suppressed as experiments at pH 11 show. In addition, deswelling effects also occur within the swelling curves, which enhance with increasing transglutaminase treatment time and are ascribed to the elastic network of cross-linked caseins. We propose a structural model for transglutaminase-treated microparticles consisting of a core of uncross-linked and a shell of cross-linked caseins. A dynamic model describes all swelling curves by considering both casein fractions in parallel. The characteristic correlation length of the internal structure of swollen casein microparticles is pH-independent and decreases with increasing transglutaminase treatment time, as observed also for the equilibrium swelling value of uncross-linked caseins.

Transepithelial Enhanced Fluence Pulsed Light M Accelerated Crosslinking for Early Progressive Keratoconus with Chemically Enhanced Riboflavin Solutions and Air Room Oxygen.

PURPOSE: To assess the 3-year clinical results of the 18 mW 7 J/cm2 transepithelial enhanced fluence pulsed light M accelerated crosslinking in the treatment of progressive keratoconus (KC) with chemically enhanced hyper-concentrated riboflavin solutions without iontophoresis and with air-room oxygenation. SETTING: Siena Crosslinking Center, Siena, Italy. METHODS: Prospective pilot, open non-randomized interventional study including 40 eyes of 30 young adult patients over 21 years old (10 simultaneous bilateral) with early (Stage I and II) progressive KC undergoing TE-EFPL 18 mW/7 J/cm2 ACXL (EFPL M TECXL). The 12 min and 58 s pulsed light (1 s on/1 s off) UV-A exposure treatments were performed with a biphasic corneal soaking using Paracel I 0.25% for 4 min and Paracel II 0.22% for 6 min riboflavin solutions and New KXL I UV-A emitter (Glaukos-Avedro, Waltham, USA) at an air room of 21% oxygenation. All patients completed the 3-year follow-up. RESULTS: CDVA showed a statistically significant improvement in the third postoperative month (Δ + 0.17 d. e.) with a final gain of +0.22 d. eq. AK showed a statistically significant decrease in the sixth postoperative month (Δ - 1.15 diopters). K itmax showed a statistically significant decrease at 1-year follow-up (Δ - 1.3 diopters). The coma value improved significantly by the sixth month (Δ - 0.54 µm). MCT remained stable during the entire follow-up. No adverse events were recorded. Corneal OCT revealed a mean demarcation line depth at 282.6 ± 23.6 µm. CONCLUSIONS: Transepithelial enhanced fluence pulsed light M accelerated crosslinking with chemically enhanced riboflavin solution halted KC progression in young adult patients without iontophoresis and no intraoperative oxygen supplementation addressing the importance of increased fluence.

Theranostic-guided corneal cross-linking: Preclinical evidence on a new treatment paradigm for keratoconus.

Theranostics is an emerging therapeutic paradigm of personalized medicine; the term refers to the simultaneous integration of therapy and diagnostics. In this work, theranostic-guided corneal cross-linking was performed on 10 human sclero-corneal tissues. The samples were soaked with 0.22% riboflavin formulation and underwent 9 minutes UV-A irradiance at 10 mW/cm2 using theranostic device, which provided both a measure of corneal riboflavin concentration and a theranostic score estimating treatment efficacy in real time. A three-element viscoelastic model was developed to fit the deformation response of the cornea to air-puff excitation of dynamic tonometry and to calculate the mean corneal stiffness parameter before and after treatment. Significant correlation was found between the theranostic score and the increase in mean corneal stiffness (R = 0.80; P < .001). Accuracy and precision of the theranostic score in predicting the induced corneal tissue stiffening were both 90%. The riboflavin concentration prior to starting the UV-A photo-therapy phase was the most important variable to allow corneal cross-linking to be effective. Theranostic UV-A light mediated imaging and therapy enables the operator to adopt a precise approach for achieving highly predictable biomechanical strengthening on individual corneas.

Recent Progress on Modified Gum Katira Polysaccharides and Their Various Potential Applications.

Gum katira polysaccharide is biocompatible and non-toxic, and has antioxidant, anti-microbial, and immunomodulatory properties. It is a natural polysaccharide and exudate derived from the stem bark of Cochlospermum reliogosum Linn. Additionally, it has many traditional medicinal uses as a sedative and for the treatment of jaundice, gonorrhea, syphilis, and stomach ailments. This article provides an overview of gum katira, including its extraction, separation, purification, and physiochemical properties and details of its characterization and pharmacognostic features. This paper takes an in-depth look at the synthetic methods used to modify gum katira, such as carboxymethylation and grafting triggered by free radicals. Furthermore, this review provides an overview of its industrial and phytopharmacological applications for drug delivery and heavy metal and dye removal, its biological activities, its use in food, and the potential use of gum katira derivatives and their industrial applications. We believe researchers will find this paper useful for developing techniques to modify gum katira polysaccharides to meet future demands.

Intervention mechanism of self-degradation of ready-to-eat sea cucumber by adding green tea extract and gallic acid.

Gallic acid (GA) and green tea extract (GT) could retard the self-degradation of ready-to-eat sea cucumber (RSC). The physical and chemical properties of RSC were changed after cross-linking. Cross-linkers could retard the conversion of α-helix like structure to random coil. Besides, the peptides of cross-linked RSC were easily broken at the sites of G, E, A, L, S, H, Y, V and I after stored for 30 d. The self-degradation rate of RSC before and after cross-linking was determined by synthetic typical peptides. After cross-linked by GA, the relative peak heights of NQ, NL and GLQ increased by 20.59%, 11.14% and 31.49%, indicating that GA could effectively retard the degradation of the peptides during storage. Moreover, hydrogen bond was confirmed as the main force to maintain the stability of RSC body wall before and after cross-linking.

Assessing corneal cross-linking with reverberant 3D optical coherence elastography.

SIGNIFICANCE: Corneal cross-linking (CXL) is a well-known procedure for treating certain eye disorders such as keratoconus. However, characterization of the biomechanical changes in the cornea as a result of this procedure is still under active research. Specifically, there is a clinical need for high-resolution characterization of individual corneal layers. AIM: A high-resolution elastography method in conjunction with a custom optical coherence tomography system is used to track these biomechanical changes in individual corneal layers. Pre- and post-treatment analysis for both low-dose and high-dose CXL experiments are performed. APPROACH: A recently developed elastography technique that utilizes the theory of reverberant shear wave fields, with optical coherence tomography as the modality, is applied to pig corneas ex vivo to evaluate elasticity changes associated with corneal CXL. Sets of low-dose and high-dose CXL treatments are evaluated before and after treatments with three pairs of pig corneas per experiment. RESULTS: The reverberant three-dimensional (3D) optical coherence elastography (OCE) technique can identify increases in elasticity associated with both low-dose and high-dose CXL treatments. There is a notable graphical difference between low-dose and high-dose treatments. In addition, the technique is able to identify which layers of the cornea are potentially affected by the CXL procedure and provides insight into the nonlinearity of the elasticity changes. CONCLUSIONS: The reverberant 3D OCE technique can identify depth-resolved changes in elasticity of the cornea associated with CXL procedures. This method could be translated to assess and monitor CXL efficacy in various clinical settings.