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Determining the efficacy of corneal crosslinking in progressive keratoconus
摘要： Objective: To determine the Efficacy of Corneal Crosslinkage (CXL), using Corneal Topography, in eyes with progressive Keratoconus. Methods: This randomized control trial was conducted at Armed Forces Institute of Ophthalmology, Rawalpindi, Pakistan from October 2013 to April 2014. A total of 60 eyes of 30 patients were included who presented with bilateral progressive Keratoconus. Each eye of the patient was randomized either to a treatment group (Group-A) or control untreated group (GroupB) of 30 eyes each. A written informed consent was obtained from each patient, following which corneal crosslinkage (CXL) with topical riboflavin eye drops was performed. Follow up visit was done at three months post operatively, Corneal topography was repeated and recorded. Results: The mean age of the patients was 23.13±7.62 years (range 13 to 39 years). There were 26 males and 34 females patients. The mean simK value at the start of study was 50.94±4.84 diopters in Group-A and 49.73±5.24 diopters in Group-B. At three months follow-up, the mean simK value was significantly lower in Group-A (48.28±4.47) as compared to Group-B (51.11±4.85). Keratoconus improved/ remained stable in 34 (56.7%) eyes while progressive disease was noted in 26 (43.3%) eyes. When compared between the groups, the frequency of efficacy was significantly higher in Group-A (86.7% vs. 26.7%; p=.000) as compared to Group-B. Conclusion: Corneal Crosslinking was found effective in causing regression or halting the progression of disease in patients with progressive Keratoconus at three months follow-up , however, the efficacy of corneal crosslinking was unaffected by patient’s age and gender.
关键词： Corneal Crosslinking,Efficacy,Keratoconus
更新于2025-09-23 15:22:29
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Analysis of Network Structures in Thiol-Ene UV Curing System Using Reworkable Resins
摘要： An analysis of the network structures in thiol-ene UV curing resins was carried out using reworkable resins composed of di(meth)acrylate monomers having tertiary ester linkages. The effect of the functionality of the thiols, the functional ratio of the thiol and ene functions, their conversions and curing atmosphere on the chain lengths was discussed. A mixture of (meth)acrylates, thiol compounds, a photoradical initiator, and a photoacid generator was cured by irradiation at 365 nm. The cured samples were degraded by heating after irradiation at 254 nm. Size exclusion chromatography (SEC) and 1H NMR analyses of the degraded samples were carried out after the methylation. The crosslinking conditions strongly affected the network structures. The degraded samples have molecular weights between 250 and 2700. The molecular weights of the degraded resins increased with the functionality of the thiol compounds. The chain length dependence suggests that thiol compounds with a high functionality have a low reactivity due to steric hindrance. The chain lengths of the degraded networks were nearly proportional to the concentration of the (meth)acrylate monomers. The addition of reactive diluents enhanced the reactivity and increased the chain length.
关键词： thiol-ene reaction,UV curing,crosslinking,chain length,degradation,reworkability
更新于2025-09-23 15:22:29
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Novel Gap Filling BARC with High Chemical Resistance
摘要： In the recent of the semiconductor manufacturing process, variety of properties (narrow gap-filling and planarity etc.) are required to organic BARC in addition to the conventional requirements. Moreover, SC-1 resistance is also needed because BARC is often used as a wet etching mask when TiN processing. But conventional BARC which include crosslinker does not have enough SC-1 resistance, and we found that it is also difficult to obtain good gap-filling and good planarity because of outgassing and film shrinkage derived from the crosslinker. In this study, we have developed the new self-crosslinking BARC. The new crosslinking system shows low outgassing and film shrinkage because of not including crosslinker. So, novel BARC has better gap filling property and planarity and over 3 times higher SC-1 resistance than that of conventional BARC. Moreover, by adding the low molecular weight additive which has high adhesive unit to TiN surface, the novel BARC has over 10 times higher SC-1 resistance than that of conventional BARC. And this novel BARC can be applied both ArF & KrF lithography process because of broad absorbance, high etching rate, chemical resistance (SC-1, SC-2, DHF, and others) and good film thickness uniformity. In this paper, we will discuss the detail of new self-crosslinking BARC in excellent total performance and our approach to achieve high chemical resistance.
关键词： KrF,ArF,Self-crosslinking,Gap filling,Planarity,Chemical resistance,BARC
更新于2025-09-23 15:22:29
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Excimer laser treatment combined with riboflavin ultraviolet-A (UVA) collagen crosslinking (CXL) in keratoconus: a literature review
摘要： Purpose To review the clinical outcome of keratoconus patients after excimer laser treatment with combined riboflavin UV-A collagen crosslinking (CXL) treatment was reviewed in light of the UDVA, CDVA and HOA. Methods Following a PubMed-based literature review of studies on excimer laser treatment with combined riboflavin UV-A CXL published between 2009 and 2018, peer-reviewed English-written studies were evaluated using the GRADE approach (www.gradeworkinggroup.org). The current review focused on the change in the (un)corrected distance visual acuity (UDVA; CDVA) and higher-order aberrations (HOA) as well as the prevalence of postoperative complications. Results Five studies with a total of 573 eyes were included, thereby reporting on 479 eyes were treated with the aforementioned combination therapy. The control group consisted of 94 eyes in total. Changes between pre- and postoperative CDVA and/or UDVA were statistically significant in all five studies after at least a 24-month follow-up period for the combined excimer laser-assisted CXL treatment in comparison with the CXL-only treatment option. Three studies described statistically significant reduction in the number of total HOA, in particular, those related to coma and spherical aberration. Corneal haze was reported in four studies, but the condition was successfully treated in all cases. Conclusion Current studies suggest that CDVA, UDVA and HOA in low-to-moderate keratoconic patients improved in a combined treatment without sacrificing biomechanical stability of the cornea. However, long-term results are needed, as the studies in our review have a follow-up period of 68 months or less.
关键词： Refractive surgery,Keratoconus,Collagen-crosslinking,Photorefractive keratectomy
更新于2025-09-23 15:21:01
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Exploiting Wavelength Orthogonality for Successive Photoinduced Polymerization-Induced Self-Assembly and Photo-Crosslinking
摘要： We report a facile benchtop process for the synthesis of cross-linked polymeric nanoparticles by exploiting wavelength-selective photochemistry to perform orthogonal photoinduced polymerization-induced self-assembly (Photo-PISA) and photo-crosslinking processes. We first established that the water-soluble photocatalyst, zinc meso-tetra(N-methyl-4-pyridyl) porphine tetrachloride (ZnTMPyP) could activate the aqueous PET-RAFT dispersion polymerization of hydroxypropyl methacrylate (HPMA). This photo-PISA process could be conducted under low energy red light (λ max = 595 nm, 10.2 mW/cm2) and without deoxygenation due to the action of the singlet oxygen quencher, biotin (vitamin B7), which allowed for the synthesis of a range of nanoparticle morphologies (spheres, worms, and vesicles) directly in 96-well plates. To perform wavelength selective nanoparticle cross-linking, we added the photoresponsive monomer, 7-[4-(trifluoromethyl)coumarin] methacrylamide (TCMAm) as a comonomer without inhibiting the evolution of the nanoparticle morphology. Importantly, under red light, exclusive activation of the photo-PISA process occurs, with no evidence of TCMAm dimerization under these conditions. Subsequent switching to a UV source (λ max = 365 nm, 10.2 mW/cm2) resulted in rapid cross-linking of the polymer chains, allowing for retention of the nanoparticle morphology in organic solvents. This facile synthesis of cross-linked spheres, worms, and vesicles demonstrates the utility of orthogonal light-mediated chemistry for performing decoupled wavelength selective chemical processes.
关键词： photoinduced polymerization-induced self-assembly,wavelength orthogonality,polymeric nanoparticles,photo-crosslinking,PET-RAFT polymerization
更新于2025-09-23 15:21:01
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Effect of molecular weight on the feature size in organic ice resists
摘要： The feature size of patterns obtained by electron beam lithography (EBL) depends critically on resist properties, beam parameters, development process, and instrument limitations. Frozen layers of simple organic molecules such as n-alkanes behave as negative tone resists for EBL. With the unique advantage of an in-situ thermal treatment replacing chemical development, the entire lithographic process can be performed within a single instrument, thus removing the influence of chemical developers on the feature size. By using an environmental transmission electron microscope, we can also minimize the influence of instrumental limitations and explore the fundamental link between resist characteristics and feature size. Our results reveal that the onset dose of organic ice resists correlates with the inverse molecular weight, and that in the thermal development the role of change in solubility of polymers is mirrored in a shift in the solid/vapour critical temperature of organic ices. With a 0.4 pA beam current we obtained 4.5 nm, 5.5 nm, 8.5 nm, lines with frozen octane, undecane, and tetradecane, respectively, consistent with the predictions of a model we developed that links beam profile and feature size. The knowledge acquired on the response of small organic molecules to electron irradiation, combined with the flexibility and operational advantages of using them as qualified EBL resists, provide us with new opportunities for the design and production of nanodevices, and broadens the reach of EBL especially towards biological applications.
关键词： crosslinking,exposure mechanism,organic ice resist,transmission electron microscopy,E-beam lithography,condensed organic molecules
更新于2025-09-23 15:21:01
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Intermolecular crosslinking of abnormal prion protein is efficiently induced by a primuline-sensitized photoreaction
摘要： In prion diseases, infectious pathogenic particles that are composed of abnormal prion proteins (PrPSc) accumulate in the brain. PrPSc is biochemically characterized by its protease-resistance core (PrPres), but its structural features have not been fully elucidated. Here, we report that primuline, a fluorescent dye with photosensitization activity, dramatically enhances UV-irradiation-induced SDS-resistant PrPSc/res oligomer formation that can be detected by immunoblot analysis of prion-infected materials. This oligomer formation occurs specifically with PrPSc/res but not with normal prion protein, and it was demonstrated using purified PrPSc/res as well as unpurified materials. The oligomer formation proceeded in both primuline-dose- and UV irradiation time-dependent manners. Treatment with urea or formic acid did not break oligomers into monomers. Neither did the presence of aromatic amino acids modify oligomer formation. Analysis with a panel of anti-prion protein antibodies showed that the antibodies against the N-terminal region of PrPres were less reactive in the dimer than the monomer. These findings suggest that the primuline-sensitized photoreaction enhances intermolecular crosslinking of PrPSc/res molecules at a hydrophobic area of the N-terminal region of PrPres. In the screening of other compounds, photoreactive compounds such as luciferin exhibited a similar but lower activity with respect to oligomer formation than primuline. The enhanced photoreaction with these compounds will be useful for evaluating the structural features of PrPSc/res, especially the interactions between PrPSc/res molecules.
关键词： interface,oligomer,fibril,amyloid,crosslinking,prion
更新于2025-09-23 15:21:01
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Development, optimization and structural characterization of an efficient peptide-based photoaffinity crosslinking reaction for generation of homogeneous conjugates from wild-type antibodies
摘要： Site-specific conjugation of small molecules to antibodies represents an attractive goal for the development of more homogeneous targeted therapies and diagnostics. Most site-specific conjugation strategies require modification or removal of antibody glycans or interchain disulfide bonds or engineering of an antibody mutant that bears a reactive handle. While such methods are effective, they complicate the process of preparing antibody conjugates and can negatively impact biological activity. Herein, we report the development and detailed characterization of a robust photoaffinity crosslinking method for site-specific conjugation to fully-glycosylated wild-type antibodies. The method employs a benzoylphenylalanine (Bpa) mutant of a previously-described 13-residue peptide derived from phage display to bind tightly to the Fc domain; upon UV irradiation, the Bpa residue forms a diradical that reacts with the bound antibody. First, we describe the initial discovery of an effective Bpa mutant peptide and optimization of reaction conditions to enable efficient conjugation without concomitant UV-induced photodamage of the antibody. Second, we assessed the scope of the photoconjugation reaction across different human and non-human antibodies and antibody mutants. Third, the specific site of conjugation on a human antibody was characterized in detail by mass spectrometry experiments and at atomic resolution by X-ray crystallography. Finally, we adapted the photoconjugation method to attach a cytotoxic payload site-specifically to a wild-type antibody and show that the resulting conjugate is both stable in plasma and as potent as a conventional antibody drug conjugate in cells, portending well for future biological applications.
关键词： wild-type antibodies,Fc domain,photoaffinity crosslinking,site-specific conjugation,antibody-drug conjugates
更新于2025-09-23 15:19:57
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Riboflavin/ultraviolet A-induced collagen cross-linking in rabbit corneal scar
摘要： ● AIM: To evaluate the biomechanical stability of the corneal scar treating with riboflavin and ultraviolet A (UVA). ● METHODS: Totally 86 New Zeal rabbits were divided into control group (group A, n=8) and trauma groups [group B (n=27), group C (n=24) and group D (n=27)]. Then groups B, C and D were divided into three sub-groups according to the time points of sacrifice, i.e. groups Ba, Ca and Da (4wk, n=8); Bb, Cb and Db (6wk, n=8); Bc (n=11), Cc (n=8) and Dc (8wk, n=11). The right corneas of these 78 rabbits in the trauma groups were penetrated. Group B were only sutured. Group C were treated with corneal cross-linking (CXL) immediately after suturing. Group D were treated with CXL seven days after suturing. The corneal scar strips of 4.0×10.0 mm2 were cut and the stress and Young’s modulus at 10% strain were evaluated. Samples from the three rabbits of group Bc and three of group Dc were used to measure the expression of alpha smooth muscle action (α-SMA). ● RESULTS: The mechanical strength of the corneal scar increased with time, and was strongest at 8wk after the injury. The ultimate stress of corneal scar (group D) were 2.17±0.52 MPa, 2.92±0.63 MPa, and 4.21±0.68 Mpa at 4wk, 6wk and 8wk, respectively; Young’s modulus were 10.94±1.57 MPa, 11.16±2.50 MPa, and 13.36±2.10 Mpa, which were higher than that of other groups except for normal control. The expression of α-SMA in group B and group D were 0.28±0.11 and 0.65±0.20, respectively, and the difference was statistically significant (P=0.048). ● CONCLUSION: CXL with riboflavin/UVA at seven days after suturing improved the biomechanical properties of corneal scars most effectively in the present study.
关键词： corneal penetrating injury,biomechanics,crosslinking,cornea,rabbit
更新于2025-09-19 17:15:36
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Modeling the Optimal Conditions for Improved Efficacy and Crosslink Depth of Photo-Initiated Polymerization
摘要： Optimal conditions for maximum ef?cacy of photoinitiated polymerization are theoretically presented. Analytic formulas are shown for the crosslink time, crosslink depth, and ef?cacy function. The roles of photoinitiator (PI) concentration, diffusion depth, and light intensity on the polymerization spatial and temporal pro?les are presented for both uniform and non-uniform cases. For the type I mechanism, higher intensity may accelerate the polymer action process, but it suffers a lower steady-state ef?cacy. This may be overcome by a controlled re-supply of PI concentration during the light exposure. In challenging the conventional Beer–Lambert law (BLL), a generalized, time-dependent BLL (a Lin-law) is derived. This study, for the ?rst time, presents analytic formulas for curing depth and crosslink time without the assumption of thin-?lm or spatial average. Various optimal conditions are developed for maximum ef?cacy based on a numerically-?t A-factor. Experimental data are analyzed for the role of PI concentration and light intensity on the gelation (crosslink) time and ef?cacy.
关键词： optimal ef?cacy,crosslinking,polymerization modeling,photoinitiator,kinetic
更新于2025-09-19 17:15:36