Preparation and stability of pegylated poly(S-alkyl-L-homocysteine) coacervate core micelles in aqueous media.

We report development and preparation of synthetic polypeptide based, coacervate core polyelectrolyte complex micelles, PCMs, in aqueous media, which were characterized and evaluated for the encapsulation and in vitro release of a model single-stranded RNA, polyadenylic acid, poly(A). Cationic, α-helical polypeptides pegylated at their N-termini, PEG113-b-5bn and PEG113-b-5cn, were designed to form coacervate core PCMs upon mixing with multivalent anions in aqueous media. Sodium tripolyphosphate (TPP) and poly(A) were used as model multivalent anions that allowed optimization of polypeptide composition and chain length for formation of stable, nanoscale PCMs. PEG113-b-5c27 was selected for preparation of PCMs that were characterized under different environmental conditions using dynamic light scattering, atomic force microscopy and cryoelectron microscopy. The PCMs were found to efficiently encapsulate poly(A), were stable at physiologically relevant pH and solution ionic strength, and were able to release poly(A) in the presence of excess polyvalent anions. These PCMs were found to be a promising model system for further development of polypeptide based therapeutic delivery vehicles.

Poly(dehydroalanine): Synthesis, Properties, and Functional Diversification of a Fluorescent Polypeptide.

Via the design of a new, soluble poly(S-alkyl-l-cysteine) precursor, a route was developed for the successful preparation of long-chain poly(dehydroalanine), ADH, as well as the incorporation of dehydroalanine residues and ADH segments into copolypeptides. Based on experimental and computational data, ADH was found to adopt a previously unobserved "hybrid coil" structure, which combines the elements of 25-helical and 310-helical conformations. Analysis of the spectroscopic properties of ADH revealed that it possesses a strong inherent blue fluorescence, which may be amenable for use in imaging applications. ADH also contains reactive electrophilic groups that allowed its efficient modification to functionalized polypeptides after reactions under mild conditions with thiol and amine nucleophiles. The combined structural, spectroscopic, and reactivity properties of ADH make it a unique reactive and fluorescent polypeptide component for utilization in self-assembled biomaterials.

Active Controlled and Tunable Coacervation Using Side-Chain Functional α-Helical Homopolypeptides.

We report the development of new side-chain amino acid-functionalized α-helical homopolypeptides that reversibly form coacervate phases in aqueous media. The designed multifunctional nature of the side-chains was found to provide a means to actively control coacervation via mild, biomimetic redox chemistry as well as allow response to physiologically relevant environmental changes in pH, temperature, and counterions. These homopolypeptides were found to possess properties that mimic many of those observed in natural coacervate forming intrinsically disordered proteins. Despite ordered α-helical conformations that are thought to disfavor coacervation, molecular dynamics simulations of a polypeptide model revealed a high degree of side-chain conformational disorder and hydration around the ordered backbone, which may explain the ability of these polypeptides to form coacervates. Overall, the modular design, uniform nature, and ordered chain conformations of these polypeptides were found to provide a well-defined platform for deconvolution of molecular elements that influence biopolymer coacervation and tuning of coacervate properties for downstream applications.

Modification of Poly(5,6-epoxy-l-norleucine) Gives Functional Polypeptides with Alternative Side-Chain Linkages.

The preparation and characterization of a new epoxide containing polypeptide, poly(5,6-epoxy-l-norleucine), via postpolymerization modification of poly(l-homoallylglycine) is described. Addition of thiols to the epoxide groups in poly(5,6-epoxy-l-norleucine) was studied as a means to prepare side-chain functional polypeptides. The solution properties of the derivatized polypeptides were studied in water and compared to similar thioether containing functional polypeptides prepared via different routes. Subtle differences in side-chain linkage chemistry were found to influence polypeptide solubility, chain conformation in solution, and thermoresponsive behavior. Poly(5,6-epoxy-l-norleucine) was found to be useful as a readily prepared intermediate that can be reacted with thiols to give a variety of functional polypeptides.

A comparison of venturi and peristaltic based phacoemulsification efficiency in routine femtosecond laser cataract surgery.

OBJECTIVE: To compare the efficiency of venturi and peristaltic pump phacoemulsification systems in patients undergoing routine laser cataract surgery. DESIGN: Single center, nonrandomized clinical study. PARTICIPANTS: The study compared consecutive eyes with moderate nuclear sclerosis undergoing routine laser cataract surgery at the Outpatient Eye Center, Mercy Health System, Springfield, MO, USA. METHODS: Each surgery used the same femtosecond laser settings. Surgeries were performed with either a venturi or peristaltic vacuum system by a single surgeon (WJS). The EFX, percent power, ultrasound time (UST), the total time that the phaco tip was in the eye (phaco tip in/out time, PIOT), and the surgery time (speculum in/out time) were recorded. Exclusions and intraoperative complications were also analyzed. RESULTS: 995 eyes were included in the study. The EFX in the venturi eyes (1.7 ± 1.3; n = 521) compared to peristaltic eyes (2.1 ± 1.4; n = 474) was lower (p < 0.0001). Similarly, the UST in the eyes performed with the venturi system versus the peristaltic system was reduced (32.4 ± 22.3 s vs 40.7± 25.7 s; p < 0.0001). The PIOT in the venturi group compared to the peristaltic group was less (71.1 ± 31.1 sec vs 79.1 ± 36.1 s; p = 0.0002). The case time (speculum in/out time) was lower for the venturi eyes (307.2 ± 68.8 s vs. 311.6 ± 53.6 s; p = 0.268). CONCLUSION: In eyes undergoing routine laser cataract surgery, the use of the venturi pump system was more efficient compared to the peristaltic pump system based on energy use and time, and there was no significant difference in complications.

Outcome of astigmatism correction using femtosecond laser combined with cataract surgery: penetrating vs intrastromal incisions.

PURPOSE: To compare the effectiveness of penetrating vs intrastromal femtosecond laser corneal relaxing incisions (CRIs) in reducing corneal astigmatism during cataract surgery. SETTINGS: Baylor College of Medicine and Mercy Clinic Eye Specialists. DESIGN: Prospective randomized study. METHODS: 248 eyes from 248 patients were included. Patients were randomly assigned to undergo paired penetrating (8 mm optical zone [OZ] at 1 center and 9 mm OZ at the other) or intrastromal CRIs (8 mm OZ at both centers). The lengths of the CRIs were based on published nomograms but modified to take into account posterior corneal astigmatism. Vector analysis was performed, and net corneal changes along the CRI meridian were calculated. Multiple regression analysis was performed to assess factors contributing to net corneal changes. RESULTS: Preoperatively, 9% to 18% of eyes had corneal astigmatism of ≤0.5 diopters (D), and 76% to 93% of eyes had postoperative refractive astigmatism of ≤0.5 D ( P < .05). Both penetrating and intrastromal CRIs produced significant mean net corneal changes along the CRI meridian (-0.49 to -1.21 D), and 71% to 84% of eyes had postoperative astigmatism vector prediction errors of ≤0.50 D. The 8 mm penetrating CRIs induced greater net corneal changes but more eyes with overcorrection than did the intrastromal and 9 mm penetrating CRIs (all P < .05). Greater net corneal changes occurred with longer CRI length, higher preoperative corneal astigmatism magnitude, and preoperative against-the-rule corneal astigmatism. Nomograms based on anterior and total corneal astigmatism are proposed. CONCLUSIONS: Both penetrating and intrastromal CRIs were effective in reducing corneal astigmatism during cataract surgery.

The Latest Evidence with Regards to Femtosecond Laser-Assisted Cataract Surgery and Its Use Post 2020.

Femtosecond laser-assisted cataract surgery (FLACS) was introduced with the hope of making cataract surgery safer and making the refractive result more predictable. It is only in the last four years that level 1 prospective randomised controlled trials (RCT) using current technology have been published. These, along with a meta-analysis of recent studies have shown that there seems to be little long-term visual benefit when using FLACS with monofocal lenses. The promised decrease in ultrasound energy required to remove a cataract has not been consistently demonstrated. There is level one evidence that the rate of posterior capsular rupture is less with FLACS using modern software. The round capsulotomy may be of increasing importance with the uptake of toric, multifocal and extended depth of focus lenses where a predictable capsulotomy size and precise placement of the lens becomes more important.

Povidone iodine treatment is deleterious to human ocular surface conjunctival cells in culture.

OBJECTIVE: To determine the effect of povidone iodine (PI), an antiseptic commonly used prior to ocular surgery, on viability of mixed populations of conjunctival stratified squamous and goblet cells, purified conjunctival goblet cells and purified conjunctival stromal fibroblasts in primary culture. METHODS AND ANALYSIS: Mixed population of epithelial cells (stratified squamous and goblet cells), goblet cells and fibroblasts were grown in culture from pieces of human conjunctiva using either supplemented DMEM/F12 or RPMI. Cell type was evaluated by immunofluorescence microscopy. Cells were treated for 5 min with phosphate-buffered saline (PBS); 0.25%, 2.5%, 5% or 10% PI in PBS; or a positive control of 30% H2O2. Cell viability was determined using Alamar Blue fluorescence and a live/dead kit using calcein/AM and ethidium homodimer-1 (EH-1). RESULTS: Mixed populations of epithelial cells, goblet cells and fibroblasts were characterised by immunofluorescence microscopy. As determined with Alamar Blue fluorescence, all concentrations of PI significantly decreased the number of cells from all three preparation types compared with PBS. As determined by calcein/EH-1 viability test, mixed populations of cells and fibroblasts were less sensitive to PI treatment than goblet cells. All concentrations of PI, except for 0.25% used with goblet cells, substantially increased the number of dead cells for all cell populations. The H2O2 control also significantly decreased the number and viability of all three types of cells in both tests. CONCLUSION: We conclude that PI, which is commonly used prior to ocular surgeries, is detrimental to human conjunctival stratified squamous cells, goblet cells and fibroblasts in culture.

The Clinical Relationship of Anterior Capsular Tears and Vertical Spacing in the Femtosecond Laser Capsulotomy Procedure.

PURPOSE: To evaluate the frequency of anterior capsule tears and capsule edge irregularities in femtosecond laser anterior capsulotomy, including the effect of optimized vertical spacing settings. METHODS: Three thousand eight hundred thirty-four cases were examined and grouped according to the femtosecond laser capsulotomy settings using manufacturer default settings with a vertical spacing of 10, 15, and 20 µm. Capsulotomy edge irregularities and anterior capsule tears were recorded intraoperatively. RESULTS: The anterior capsule tear rates for the 10, 15, and 20 µm groups were 0.79%, 0.35%, and 0.09%, respectively. The capsule edge irregularity rates for the 10, 15, and 20 µm groups were 6.25%, 1.13%, and 1.15%, respectively. The treatment times for the 10, 15, and 20 µm groups were 1.6, 0.7, and 0.8 second, respectively. The risk reduction of anterior capsule tears positively correlated with the 15 and 20 µm group settings. The anterior capsule tear rate difference between the 10 and 20 µm group settings was statistically significant. Capsule edge irregularity rates were reduced in the 15 and 20 µm group settings. Eye movement was monitored in the 20 µm group and was observed in 9 of 13 patients with capsule edge irregularities. CONCLUSIONS: Anterior capsule tear rates are low with femtosecond laser cataract surgery. The rate can be further reduced with optimization of the settings, including an increase in vertical spacing. [J Refract Surg. 2019;35(5):280-284.].

Greater vertical spot spacing to improve femtosecond laser capsulotomy quality.

PURPOSE: To evaluate the effect of adapted capsulotomy laser settings on the cutting quality in femtosecond laser-assisted cataract surgery. SETTING: Ruhr-University Eye Clinic, Bochum, Germany. DESIGN: Prospective randomized case series. METHODS: Eyes were treated with 1 of 2 laser settings. In Group 1, the regular standard settings were used (incisional depth 600 µm, pulse energy 4 µJ, horizontal spot spacing 5 µm, vertical spot spacing 10 µm, treatment time 1.2 seconds). In Group 2, vertical spot spacing was increased to 15 µm and the treatment time was 1.0 seconds. Light microscopy was used to evaluate the cut quality of the capsule edge. The size and number of tags (misplaced laser spots, which form a second cut of the capsule with high tear risk) were evaluated in a blinded manner. Groups were compared using the Mann-Whitney U test. RESULTS: The study comprised 100 eyes (50 eyes in each group). Cataract surgery was successfully completed in all eyes, and no anterior capsule tear occurred during the treatment. Histologically, significant fewer tags were observed with the new capsulotomy laser setting. The mean score for the number and size of free tags was significantly lower in this group than with the standard settings (P < .001). CONCLUSIONS: The new laser settings improved cut quality and reduced the number of tags. The modification has the potential to reduce the risk for radial capsule tears in femtosecond laser-assisted cataract surgery. With the new settings, no tags and no capsule tears were observed under the operating microscope in any eye.

Comparison of vitreous loss rates between manual phacoemulsification and femtosecond laser-assisted cataract surgery.

PURPOSE: To compare the vitreous loss complication rate of manual phacoemulsification cataract surgery with that of femtosecond laser-assisted cataract surgery. SETTING: Mercy Eye Specialists, Springfield, Missouri, USA. DESIGN: Retrospective single-center case series. METHODS: Cataract surgeries from 2010 to 2014 performed by 4 surgeons were audited for rates of vitreous loss. Vitreous loss data were statistically analyzed with and without exclusions. RESULTS: Of the total 7155 cases from 2010 to 2014, 3784 were consecutively performed using manual phacoemulsification from 2010 to 2012 and 3371 were performed using femtosecond laser-assisted cataract surgery from 2013 to 2014. The rate of vitreous loss with exclusions was 1.17% in the manual phacoemulsification group and versus 0.65% femtosecond laser-assisted group; without exclusions, the rate was 1.40% versus 0.77%. In absolute terms, the rate decreased for every surgeon in the study. The chi-square test showed a statistically significant association between the date of surgery, and thus technique, and vitrectomy cases (P < .05). Odds ratio analysis with exclusions versus without exclusions indicated that surgeries performed from 2010 to 2012 using manual phacoemulsification were 1.6 times and 1.8 times, respectively, more likely to have vitreous loss than surgeries performed from 2013 to 2014 using the femtosecond laser-assisted cataract surgery technique. CONCLUSIONS: Conversion from manual phacoemulsification to femtosecond laser-assisted cataract surgery resulted in a statistically significant decrease in vitreous loss. Because vitreous loss increases the risk for other serious complications of cataract surgery, this new finding has important implications for the safety of cataract surgery. FINANCIAL DISCLOSURE: Proprietary or commercial disclosures are listed after the references.

Femtosecond laser-assisted primary posterior capsulotomy for toric intraocular lens fixation and stabilization.

UNLABELLED: We describe 2 cases in which a spontaneously rotated toric intraocular lens (IOL) was fixated and stabilized using the femtosecond laser to create a primary posterior capsulotomy for posterior optic capture. We also review the literature on previous techniques that have been used to prevent or stabilize recurrent toric IOL rotation. The design of toric IOLs must be evaluated further to determine the risk for rotation in myopic eyes. FINANCIAL DISCLOSURE: Dr. Scott is a consultant to Abbott Medical Optics, Inc. Neither author has a financial or proprietary interest in any material or method mentioned.