Studying molecular interactions via capillary electrophoresis and microscale thermophoresis: A review

The process of choosing the most proper technique for studying the molecular interactions is based on critical factors such as instrumentation complexity, automation, experimental procedures, analysis time, consumables, and cost-value. This review has tracked the use of affinity capillary electrophoresis (ACE) and microscale thermophoresis (MST) techniques in the evaluation of molecular binding between different molecules during the 5 years 2016-2021. ACE has proved to be an attractive technique for biomolecular characterization with high resolution efficiency where small variations in several controlling factors can much improve such efficiency compared to other analytical techniques. Meanwhile, MST has proved its higher sensitivity for smaller amounts of complex non-purified biosamples without affecting its robustness while providing high through output. However, the main motivation to review both techniques in the proposed review was their capability to carry out all experiments without the need for immobilizing one interacting partner, besides a great flexibility in the use of buffering systems The proposed review demonstrates the importance of both techniques in different areas of life sciences. Moreover, the recent advances in exploiting ACE and MST in other research interests have been discussed. This article is protected by copyright. All rights reserved.

EFFECT OF RANIBIZUMAB AND AFLIBERCEPT ON RETINAL PIGMENT EPITHELIAL DETACHEMENT, SUBRETINAL AND INTRARETINAL FLUID IN AGE-RELATED MACULAR DEGENERATION

PURPOSE

The aim of the study was to compare the effect of three initial doses of the anti-VEGF ranibizumab and aflibercept medication on serous pigment epithelial detachment (PED), subretinal fluid (SRF) and intraretinal fluid (IRF) in the macula of treatment naive neovascular AMD (nvAMD) patients.

MATERIAL AND METHODS

The cohort consists of 148 patients, of which 74 patients were treated with ranibizumab (51 females and 23 males) and 74 with aflibercept (46 females and 28 males). The data was recorded prospectively from the moment of diagnosis and start of treatment for a period of 3 months. At the moment of diagnosis and 3 months later, an OCT examination (Spectralis OCT, Heidelberg Engineering, Heidelberg, Germany) was performed. The OCT examination included a macular scan with 25 scans. Using the OCT instrument software, we measured the maximum anterior-posterior elevation of serous PED, the highest thickness of SRF and the largest diameter of the intraretinal cystic space. The statistical significance of differences between groups was evaluated using the t-test for continuous data and the Fisher exact test for categorical data. Changes in values of continuous variables over time were evaluated using the Wilcoxon paired test. Paired comparisons of binary parameters were determined by the McNemar test.

RESULTS

Full regression of PED, SRF and IRF occurred in 3 (4.1%), 25 (39%) and 20 (51%) patients treated with ranibizumab, and in 5 (7.9%, p = 0.470), 28 (47%, p = 0.470) and 25 (57%, p = 0.827) patients treated with aflibercept, respectively. The average regression of PED, SRF and IRF was -60.4 μm (median -37.5 μm), -84.3 μm (median -85 μm) and -109.3 μm (median -81 μm) in patients treated with ranibizumab, and -46.3 μm (median -30 μm, p = 0.389), -127.7 μm (median -104 μm, p = 0.096) and -204.4 μm (median -163 μm, p = 0.005) in patients treated with aflibercept, respectively. We did not show a statistically significant difference in the regression rates of PED, SRF and IRF between the ranibizumab and aflibercept groups. (in patients with IRF after adjustment of the higher baseline IRF volumes in patients treated with aflibercept, p = 0.891).

CONCLUSION

We are convinced that ranibizumab and aflibercept have the same effect on serous PED, SRF and IRF in the macula in patients with treatment naive nvAMD during the initial loading phase.

Toward an automated workflow for the study of plasma protein-drug interactions based on capillary electrophoresis-frontal analysis combined with in-capillary mixing of interacting partners

Capillary electrophoresis-frontal analysis (CE-FA) together with mobility shift affinity CE is the most frequently used mode of affinity CE for a study of plasma protein-drug interactions, which is a substantial part of the early stage of drug discovery. Whereas in the classic CE-FA setup the sample is prepared by off-line mixing of the interaction partners in the sample vial outside the CE instrument and after a short incubation period loaded into the capillary and analysed, in this work a new methodological approach has been developed that combines CE-FA with the mixing of interacting partners directly inside the capillary. This combination gives rise to a fully automated and versatile methodology for the characterization of these binding interactions besides a substantial reduction in the amounts of sample compounds used. The minimization of possible experimental errors due to the full involving of sophisticated CE instrument in the injection procedure, mixing and separation instead of manual manipulation is another fundamental benefit. The in-capillary mixing is based on the transverse diffusion of laminar flow profile methodology introduced by Krylov et al. using its multi-zone injection modification presented by Řemínek at al.. Actually, after the method optimization, the alternate introduction of six plugs of drug and six plugs of bovine serum protein in BGE, each injected for 3 s at a pressure of -10 mbar (-1 kPa) into the capillary filled by BGE, was found to be the best injection procedure. The method repeatability calculated as RSDs of plateau highs of bovine serum albumin and propranolol as model sample compounds were better than 3.44 %. Its applicability was finally demonstrated on the determination of apparent binding parameters of bovine serum albumin for basic drugs propranolol and lidocaine and acid drug phenylbutazone. The values obtained by a new on-line CE-FA methodology are in agreement with values estimated by classic off-line CE-FA, as well as with literature data obtained using different techniques.

Applicability of capillary electrophoresis-frontal analysis for displacement studies: Effect of several drugs on l-tryptophan and lidocaine binding to human serum albumin

The effective concentration of a drug in the blood, i.e. the concentration of a free drug in the blood, is influenced by the strength of drug binding onto plasma proteins. Besides its efficacy, these interactions subsequently influence the liberation, absorption, distribution, metabolism, excretion, and toxicological properties of the drug. It is important to not only determine the binding strength and stoichiometry, but also the binding site of a drug on the plasma protein molecule, because the co-administration of drugs with the same binding site can affect the above-mentioned concentration and as a result the pharmacological behavior of the drugs and lead to side effects caused by the change in free drug concentration, its toxicity. In this study, the binding characteristics of six drugs with human serum albumin, the most abundant protein in human plasma, were determined by capillary electrophoresis-frontal analysis, and the obtained values of binding parameters were compared with the literature data. The effect of several drugs and site markers on the binding of l-tryptophan and lidocaine to human serum albumin was investigated in subsequent displacement studies which thus demonstrated the usability of capillary electrophoresis as an automated high-throughput screening method for drug-protein binding studies.

Capillary electrophoresis-based immunoassay and aptamer assay: A review

Over the last two decades, the group of techniques called affinity probe CE has been widely used for the detection and the determination of several types of biomolecules with high sensitivity. These techniques combine the low sample consumption and high separation power of CE with the selectivity of the probe to the target molecule. The assays can be defined according to the type of probe used: CE immunoassays, with an antibody as the probe, or aptamer-based CE, with an aptamer as the probe. Immunoassays are generally divided into homogeneous and heterogeneous groups, and homogeneous variant can be further performed in competitive or noncompetitive formats. Interacting partners are free in solution at homogeneous assay, as opposed to heterogeneous analyses, where one of them is immobilized onto a solid support. Highly sensitive fluorescence, chemiluminescence or electrochemical detections were typically used in this type of study. The use of the aptamers as probes has several advantages over antibodies such as shorter generation time, higher thermal stability, lower price, and lower variability. The aptamer-based CE technique was in practice utilized for the determination of proteins in biological fluids and environmentally or clinically important small molecules. Both techniques were also transferred to microchip. This review is focused on theoretical principles of these techniques and a summary of their applications in research.

Capillary electrophoresis-based approaches for the study of affinity interactions combined with various sensitive and nontraditional detection techniques

Nearly all processes in living organisms are controlled and regulated by the synergy of many biomolecule interactions involving proteins, peptides, nucleic acids, nucleotides, saccharides, and small molecular weight ligands. There is growing interest in understanding them, not only for the purposes of interactomics as an essential part of system biology, but also in their further elucidation in disease pathology, diagnostics, and treatment. The necessity of detailed investigation of these interactions leads to the requirement of laboratory methods characterized by high efficiency and sensitivity. As a result, many instrumental approaches differing in their fundamental principles have been developed, including those based on capillary electrophoresis. Although capillary electrophoresis offers numerous advantages for such studies, it still has one serious limitation, its poor concentration sensitivity with the most commonly used detection method-ultraviolet-visible spectrometry. However, coupling capillary electrophoresis with a more sensitive detector fulfils the above-mentioned requirement. In this review, capillary electrophoresis combined with fluorescence, mass spectrometry, and several nontraditional detection techniques in affinity interaction studies are summarized and discussed, together with the possibility of conducting these measurements in microchip format.

Implantation of posterior chamber phakic intraocular lens for myopia and hyperopia - long-term clinical outcomes

PURPOSE

To evaluate long-term refractive outcomes of implantable collamer lens (ICL) implantation and late postoperative complications.

METHODS

We assessed outcomes of patients who underwent ICL implantation (type ICM V4 for myopia, ICH V3 for hyperopia, TICM V4 for astigmatism) in our department between 1998 and 2013. It comprised 62 eyes (40 myopic and 22 hyperopic). The average follow-up period was 10.5 years. We evaluated: uncorrected and best-corrected visual acuity (UCVA and BCVA), spherical equivalent (SE), ICL vault, endothelial cell density and late postoperative complications.

RESULTS

In myopes, the average UCVA was 1.0±0.37 and BCVA 1.18±0.38, in hyperopes 0.78±0.19 and 1.14±0.18, respectively. The average SE in myopes, whose target refraction was emmetropia, was -0.6±0.83 Dsf, in hyperopes +0.73±0.93. Central ICL vault was 206.16μm±105.94, (range 10-427) in myopes, 195.5μm±109.09, (range 20-404) in hyperopes. The most common late postoperative complication was cataract formation. Three myopic eyes (7.5%) developed symptomatic anterior subcapsular opacities with loss of at least two lines of BCVA. Cataract significantly affecting visual acuity occurred in 5 myopic eyes (12.5%) and 2 hyperopic eyes (9.09%). In these eyes, ICL removal and cataract surgery was performed.

CONCLUSIONS

In our experience, ICL implantation in moderate and high ametropia was effective and relatively safe. The most common late complication was cataract formation. This complication can be managed effectively surgically with good refractive outcomes without loss of BCVA.

Incidence of cataract following implantation of a posterior-chamber phakic lens ICL (Implantable Collamer Lens) - long-term results

AIM

To evaluate late postoperative complications, especially cataract occurrence, its morphological type and factors affecting its development in patients implanted with ICL (Implantable Collamer Lens).

METHODS

We analysed the results of ICL implantation in 34 patients (type ICM V4 for myopia, ICH V3 for hyperopia, TICM V4 for astigmatism) in our department between 1998 and 2013. The cohort comprised 62 eyes (40 myopic and 22 hyperopic). Seven eyes with a toric ICL implanted were included in these groups according to spherical equivalent (SE). The average follow-up period was 10.5 ± 3.5 years. We examined uncorrected and best-corrected visual acuity (UCVA and BCVA), SE, ICL vaulting (using anterior segment OCT) and occurrence of late postoperative complications, especially cataract formation in 2 groups of patients - myopes and hyperopes.

RESULTS

Among the most common late postoperative complications were pigment dispersion syndrome in 27 eyes, 43.5% (12 myopic eyes and 15 hyperopic eyes) and cataract formation. Lens opacities, including opacities without loss of BCVA, were observed in 18 eyes (29%). Opacities affecting visual acuity were observed in 10 eyes (16.1%). Cataract significantly affecting visual acuity occurred in 7 eyes, i.e. 11.3% (5 myopic eyes and 2 hyperopic eyes). In these eyes, ICL removal and cataract surgery with implantation of posterior chamber intraocular lens (PC IOL) was performed. The most common morphological type of cataract were anterior subcapsular opacities (83.3%), the average time of onset was 3.4 ± 1.9 years after ICL implantation. We did not prove a statistically significant association either between cataract occurrence and age at the time of surgery, or between cataract occurrence and higher preoperative spherical equivalent. We did not prove a significant association between cataract occurrence and low vault, however in 7 eyes after cataract surgery and ICL removal we do not know the vault values. In one eye uveitis with cystoid macular oedema was observed, in two highly myopic eyes repeated ICL dislocation and cataract occurred. In both of these cases the ICL was removed.

CONCLUSIONS

According to our experience, implantation of ICL in moderate and high ametropia was relatively safe upon assessing the long-term outcomes. Among the most common complications were pigment dispersion syndrome and anterior subcapsular cataract formation. Cataract can be managed effectively surgically with good refractive outcomes without loss of BCVA. However, loss of accommodation after cataract surgery and risk of vitreoretinal complications must be considered.Key words: ICL (Implantable Collamer Lens), posterior chamber phakic intraocular lens, refractive surgery, cataract occurrence.

Study on the interactions of sulfonylurea antidiabetic drugs with normal and glycated human serum albumin by capillary electrophoresis-frontal analysis

Diabetes is one of the most widespread diseases characterized by a deficiency in the production of insulin or its ineffectiveness. As a result, the increased concentrations of glucose in the blood lead not only to damage to many of the body's systems but also cause the nonenzymatic glycation of plasma proteins affecting their drug binding. Since the binding ability influences its pharmacokinetics and pharmacodynamics, this is a very important issue in the development of new drugs and personalized medicine. In this study, capillary electrophoresis-frontal analysis was used to evaluate the affinities between human serum albumin or its glycated form and the first generation of sulfonylurea antidiabetics, since their inadequate concentration may induce hypoglycaemia or on the contrary hyperglycaemia. The binding constants decrease in the sequence acetohexamide > tolbutamide > chlorpropamide > carbutamide both for normal and glycated human serum albumins, with glycated giving lower values. These results provide a more quantitative picture of how these drugs bind with normal and modified human serum albumin and indicate capillary electrophoresis-frontal analysis to be another tool for examining the changes arising from modifications of albumin, or any other protein, with all its benefits like short analysis time, small sample requirement, and automation.

Comparison of various capillary electrophoretic approaches for the study of drug-protein interaction with emphasis on minimal consumption of protein sample and possibility of automation

The binding ability of a drug to plasma proteins influences the pharmacokinetics of a drug. As a result, it is a very important issue in new drug development. In this study, affinity capillary electrophoresis, capillary electrophoresis with frontal analysis, and Hummel Dreyer methods with internal and external calibration were used to study the affinity between bovine serum albumin and salicylic acid. The binding constant was measured by all these approaches including the equilibrium dialysis, which is considered to be a reference method. The comparison of results and other considerations showed the best electrophoretic approach to be capillary electrophoresis-frontal analysis, which is characterized by the high sample throughput with the possibility of automation, very small quantities of biomacromolecules, simplicity, and a short analysis time. The mechanism of complex formation was then examined by capillary electrophoresis with frontal analysis. The binding parameters were determined and the corresponding thermodynamic parameters such as Gibbs free energy ΔG(0), enthalpy ΔH(0), and entropy changes ΔS(0) at various temperatures were calculated. The results showed that the binding of bovine serum albumin and salicylic acid was spontaneous, and that hydrogen bonding and van der Waals forces played a major role in the formation of the complex.

[Diagnostic pitfalls of pseudo-foster kennedy syndrome - a case report]

To the outpatient facility of the Department of Ophthalmology, Faculty Hospital Brno, Czech Republic, E.U., was in June 2013 referred a 24 years old man with the suspicion of Foster Kennedy syndrome. On the fundus examinations, the findings were in correlation with the symptoms of this syndrome: slightly pale optic disc of the right eye and edema with the anterior extension of the optic nerve head of the left eye. The perimetric examination revealed bilateral visual fields defects, mainly in the nasal parts of the visual fields which is not typical for this syndrome. The native magnetic resonance imaging (MRI) examination was negative. Due to the suspicion of pathologic finding in the visual pathway area, the blood levels of pituitary gland hormones were examined and revealed elevated prolactin levels. In the indicated MRI examination with contrast, in the revised reading, a suspicious microadenoma of the pituitary gland was detected. Due to the atypical changes in the perimetric examinations, other possible causes of visual fields defects as coincidence of multiple, each other independent pathologies (neuritis or neuropathy of the optic nerve, neuromyelitis optica (Devic disease), Lebers hereditary optic neuritis (LHON) etc.) to exclude or to confirm the Pseudo-Foster Kennedy syndrome were taken into account. The patient is regularly followed up at our outpatient facility as well as at the outpatient facility of the Department of Neurosurgery, where, until now, the follow up only was recommended. The diagnosis of this case was, until now, set as Pseudo- Foster Kennedy syndrome, with unclarified cause of the clinical findings.

[The effectiveness of corneal cross-linking in stopping the progression of keratoconus]

OBJECTIVE

Objective of the study was to prove the efficiency of corneal cross-linking (CXL) in stopping the progression of keratoconus.

METHODS

In this study were included 58 eyes of patients with progressive keratoconus who underwent CXL according to the Dresden protocol in the years 2007-2009 at the Ophthalmic clinic FN Brno Bohunice. The eyes of patients were divided into four groups according to the change of maximum curvature of the cornea two years after CXL.

RESULTS

Stabilization of maximum curvature of the cornea have been reported in 40 % of eyes, regression in 57 % of eyes by an average of 1,92D and disease progression in 3 % of eyes 2 years after CXL. The eyes with regression over 2D had significantly higher best-corrected visual acuity before and after the procedure compared to the group with stabilization. Spherical equivalent increased significantly in all groups, on average, in the group with stabilization of 0,54D, in the group with mild regression of 0,71D and in the group with a large regression of 2,09D. In the group with a large regression 100 % of eyes had stabilization or increase in SE. Our observations showed that, when a decrease in the patient keratometric values of cornea is present after CXL, it is comprehensive and applies to all parameters.

CONCLUSION

We have confirmed that corneal cross-linking stops the progression of the disease in 97 % of eyes two years after the procedure.

[Supracor, Laser Correction of Presbyopia: One-year Follow-up Outcomes]

PURPOSE

Evaluation of one-year postoperative results after Supracor laser procedure.

METHODS

The study group consisted of 8 hyperopic patients (16 eyes) seeking alternatives to wearing glasses for both distance and near vision. These patients underwent Supracor refractive surgery in the Department of Ophthalmology of The University Hospital Brno in the time period from July 2012 to February 2013. The patient mean age at operation was 57,2 years (±4,6), mean binocular uncorrected near visual acuity was Jaeger No. 13, distance visual acuity 0,5 (±0,19). Average follow-up period was 15,5 months (±2,4). We evaluated binocular uncorrected and best corrected distance visual acuity (UDVA, BCDVA), near visual acuity (UNVA, BCNVA), and intermediate visual acuity (UIVA, BCIVA) 12 months after surgery, further the stability of visual acuity, objective refraction, mesopic contrast sensitivity, occurrence of complications, and patient satisfaction.

RESULTS

In all 8 patients, binocular UDVA of at least 1,0 was achieved. The mean spherical equivalent was +0,25 D (±0,64). UNVA was Jaeger No. 3 or better in 7 patients (68,7 %), 5 of them could read Jaeger No. 1. UIVA Jaeger No. 1 was achieved in 5 patients (62,5 %), Jaeger No. 2 in 2 patients (25 %), and Jaeger No. 4 in 1 patient (12,5 %). In all eyes, preoperative mesopic contrast sensitivity was within the normal range for the given age. Postoperatively it remained within the normal range in 11 eyes (68,7 %). In 5 eyes (31,3 %) we found adecrease below the lower limit in higher spatial frequencies (12 and 18 cycles/degree) during the entire follow-up period. According to the patient questionnaire, 7 patients (87,5 %) were fully satisfied with the outcome of the surgery and they felt independent of wearing glasses, 1 patient was dissatisfied. 7 patients (87,5 %) did not report the presence of photic phenomena (halo, glare), 1 patient suffered from these problems. We did not encounter any intraoperative or postoperative complications.Conlusion: According to our first experience, good distance, near, and intermediate visual acuity and arather high patient satisfaction can be achieved with the use of the Supracor procedure. Supracor seems to be asuitable method of presbyopia correction in motivated, adaptable patients who meet strict indication criteria. With regard to the small number of patients in our study group, agreater number of patient evaluations will be required in the future, and long-term results will be of interest as well.Key words: Supracor, presbyopia, LASIK, refractive surgery.