The development of electrochemical biosensors for cholesterol

Coronary vascular disease (CVD) is the number one cause of death worldwide. According to a WHO report and global and regional projections of mortality and burden of disease, by 2030, the number of people dying from heart disease and stroke will increase to reach 23.3 million. Non-HDL cholesterol, determined by subtracting the high density lipoprotein cholesterol (HDL-C) concentration from the total cholesterol (TC) content, has been recommended as a target for preliminary CVD prevention. In recent times, single-step homogeneous assays have been developed which allow simple and selective measurement of cholesterol fractions. Electrochemical sensors have also been developed which are based on the electrocatalysis of hydrogen peroxide using low cost printed sensor methodologies and such platforms would have the potential to be used as the basis of fabricating cholesterol biosensors for point of care use.Here, the development of electrochemical biosensors for the selective measurement of HDL-C, TC, and by subtraction non-HDL-C was explored. A spectrophotometric assay for use at room temperature and with minimal sample dilution was first established in order to optimise the assay reagent components for the development of selective cholesterol assays. Assay chemistries based on polyoxyethylene tribenzylphenyl ethers (Emulgen B-66) and Triton X-100 for the selective measurement of HDL-C and TC, respectively, were developed. The impact of these reagents on the electrocatalytic reduction of hydrogen peroxide at silver paste screen printed electrodes was also evaluated and optimised.Electrochemical biosensors for HDL-C and TC using externally added assay reagents were developed by combining the homogeneous assay methodologies with the printed electrocatalytic electrodes. The effects of assay reagents such as surfactants, enzymes, HDL-C sample and delipidated serum on the electrode behaviour were assessed amperometrically in the presence of hydrogen peroxide solutions. The electrodes showed increases in their catalytic activity toward hydrogen peroxide in the presence of both selective and non-selective surfactant and decreases in the presence of cholesterol oxidase and HDL-C samples. Despite the negative effects of cholesterol oxidase and sample matrix on electrode behaviour, the electrode response was linear within the clinically relevant ranges of HDL-C and TC. The modified electrodes were evaluated for their ability to selectively measure HDL-C and TC in clinical serum samples. The resulting HDL-C biosensor yielded a sensitivity of 3.32×10-8 A/mM with a linear range of 0 to 4 mM (r2=0.999), LOD of 0.5 mM and average RSD of 9.5% (n=5) while the TC biosensor had a sensitivity of 2.24×10-8 A/mM and a linear range of 0 to 10 mM r2=0.984), LOD of 2 mM and average RSD of 10.8% (n=3). The correlation between the HDL-C sensor and a commercial laboratory assay in clinical serum samples had a slope of 0.87 and a Pearson correlation coefficient of 0.76 (n=13) while the correlation for TC measurement had a slope of 1.07 and a Pearson correlation coefficient of 0.87.Finally, in order to develop a disposable biosensor suitable for point of care testing, integrated biosensors for HDL-C and TC were fabricated by inkjet-print deposition of assay reagents on the electrode surface. Integrated biosensors for the measurement of HDL-C were optimised and yielded a sensitivity of 4.55×10-8 A/mM with a linear range of 0 to 4 mM (r2=0.993) with an LOD of 0.25 mM and average RSD of 6.6% (n=3). The integrated TC biosensor had a sensitivity of 9.38×10-9 A/mM and linear range of 0 to 9 mM (r2=0.982), LOD of 0.5 mM and average RSD of 9.5% (n=3)

A Comparison between Prophylactic Vitrectomy and Laser Photocoagulation in Treatment of Acute Retinal Necrosis Syndrome

Purpose: To compare the results of prophylactic pars plana vitrectomy with barrier laser photocoagulation in treatment of acute retinal necrosis (ARN). Patients and Methods: Fifteen ARN patients were retrospectively included in this study. At presentation, all patients had severe vitreous involvement without any detectable break or retinal detachment (RD), either in funduscopy or echography exams. All patients received intravenous acyclovir 2 g/daily for two weeks. Eight patients underwent prophylactic vitrectomy and seven patients underwent barrier laser photocoagulation after resolution of vitritis. Visual and structural outcomes were compared between the two groups. Results: In eight vitrectomized patients, one patient (12.5 %) experienced RD. The mean best corrected visual acuity (BCVA) improved significantly in this group (P=  0.027). Among seven patients undergoing barrier laser photocoagulation, 3 patients (43 %) developed RD and BCVA improvement was not significant (P=  0.207). Comparison between the two groups did not show any statistically significant benefit when comparing post treatment BCVA (P=  0.59) or RD prevention (P=  0.282). Conclusion: Early prophylactic vitrectomy, in the course of ARN has been suggested as a useful method in preventing RD and improving the visual outcome, but the results of the present study did not indicate any significant benefit for vitrectomy compared to barrier laser photocoagulation. Further studies with bigger sample size are recommended to compare these two methods of treatment.Keywords: Retinal necrosis syndrome; Acute; Treatment outcome; Vitrectomy; Retinal detachment

A biosensor for the determination of high density lipoprotein cholesterol employing combined surfactant-derived selectivity and sensitivity enhancements

High density lipoprotein cholesterol (HDL-C) is a modifiable risk factor in cardiovascular disease and devices suitable for its determination at the point of care are critical to the future management of hypercholesterolaemia. An electrochemical biosensor for measuring HDL-C was developed. The biosensor was based on a homogeneous assay methodology for selective determination of HDL-C in combination with a printed electrochemical sensor for measuring the reduction of hydrogen peroxide at a silver paste electrode. The polyoxyethylene alkylene tribenzylphenyl ether surfactant (Emulgen B-66) was found to be capable of both the selective dissolution of HDL particles, as well as the enhanced electrocatalytic reduction of hydrogen peroxide. The resulting biosensor was shown to have a linear response to HDL-C from 0.5 to 4 mM (r2=0.998) with an average r.s.d. of 7%. The biosensor was also used to analyse HDL-C in thirteen serum samples and had good agreement with a commercial spectrophotometric precipitation-based assay (r=0.7222; p < 0.058)

A survey of incidental ocular trauma by pencil and pen

AIM: To determine characteristic features of ocular trauma resulted from self-trauma by writing instruments among pediatric population. METHODS: Thirty-six children who suffered from self-inflicted ocular trauma with a writing instrument were included in this prospective cross-sectional study. RESULTS: The mean age was 5.6±2.7y with male: female ratio of 1.77. The right eye was involved two times more than the left eye. The superomedial (55.5%) and inferomedial (30.6%) quadrants were the most common sites of injury. The leading culprit was colored pencils (44.4%). During surgical exploration, no foreign body (FB) was found in 25 (69.4%) patients while an FB was found in 11 (30.5%) patients. Brain injury was present in two patients (5.6%) and only in superomedial quadrant injuries. Zone 1 was the most common site for ocular trauma associated with penetrating injury. The mean ocular trauma score (OTS) in penetrating injuries was 3.8±1.2. The best corrected visual acuity (BCVA) was 0.3±0.6 upon admittance and 0.08±0.21 after one year. The final BCVA was significantly correlated with the entrance site, better final BCVA was found in nasal entrance site (P<0.05). CONCLUSION: The ophthalmologists should keep a high index of suspicion to rule out penetrating eye injuries related to writing instruments in a young uncooperative child. Brain injury is a life-threatening event that should be ruled out by appropriate imaging. Medial canthal area as the most common site needs an especial attention in writing instrument injuries

Biomedical Diagnostics Enabled by Integrated Organic and Printed Electronics

© 2017 American Chemical Society. Organic and printed electronics integration has the potential to revolutionize many technologies, including biomedical diagnostics. This work demonstrates the successful integration of multiple printed electronic functionalities into a single device capable of the measurement of hydrogen peroxide and total cholesterol. The single-use device employed printed electrochemical sensors for hydrogen peroxide electroreduction integrated with printed electrochromic display and battery. The system was driven by a conventional electronic circuit designed to illustrate the complete integration of silicon integrated circuits via pick and place or using organic electronic circuits. The device was capable of measuring 8 μL samples of both hydrogen peroxide (0-5 mM, 2.72 × 10 -6 A·mM -1 ) and total cholesterol in serum from 0 to 9 mM (1.34 × 10 -8 A·mM -1 , r 2 = 0.99, RSD < 10%, n = 3), and the result was output on a semiquantitative linear bar display. The device could operate for 10 min via a printed battery, and display the result for many hours or days. A mobile phone "app" was also capable of reading the test result and transmitting this to a remote health care provider. Such a technology could allow improved management of conditions such as hypercholesterolemia

The evolution of selective analyses of HDL and LDL cholesterol in clinical and point of care testing

Cardiovascular disease is a leading cause of death worldwide and is caused by the build up of atherosclerotic plaques in the vasculature. It is now well established that the formation of these plaques is closely related to levels of both high density lipoprotein (HDL) and low density lipoprotein (LDL) cholesterol. Thus, the importance of the effective measurement of these is critical for the improved diagnosis and management of atherosclerosis. This review discusses the emergence of methodologies for the selective determination of both LDL and HDL cholesterol. It begins with an explanation of the first methodologies based on ultracentrifugation and precipitation techniques, the development of reference methods, through to the emergence of methodologies suitable for routine laboratory use, followed by the development of professional use, point of care technologies. Finally, the current status of selective tests for cholesterol based on biosensor methodologies is reviewed and the potential for application in consumer diagnostics is discussed. © 2013 The Royal Society of Chemistry

Measurement of total cholesterol using an enzyme sensor based on a printed hydrogen peroxide electrocatalyst

© 2016 The Royal Society of Chemistry. Cholesterol is a major modifiable risk factor in cardiovascular disease and can be effectively managed by a combination of medication and monitoring. There continues to be a need for new point-of-care diagnostics to measure lipid panels, including total cholesterol. Enzyme assays based on the generation of hydrogen peroxide have been very effective in this regard. This work demonstrates the application of printed electrochemical sensors to the measurement of total cholesterol in serum. The assay uses the surfactant Triton X-100 to provide electrocatalytic enhancement of a silver paste screen-printed electrode to hydrogen peroxide, while also achieving effective solubilisation of total cholesterol from lipoprotein. The resulting biosensors employed 0.5% (v/v) Triton X-100 in PBS with 156 U mL-1 cholesterol esterase and 60 U mL-1 cholesterol oxidase. Measurement of total cholesterol in serum in the range of 0 to 10 mM had a sensitivity of 2.24 × 10-8 A mM-1, with coefficient of determination of 0.984, detection limit of at least 2 mM and average relative standard deviation of 10.8% (n = 3)

Subfoveal Choroidal Thickness after Panretinal Photocoagulation with Red and Green Laser in Bilateral Proliferative Diabetic Retinopathy Patients: Short Term Results

Purpose. To compare subfoveal choroidal, central retinal, and peripapillary nerve fiber layer (RNFL) thickness after panretinal photocoagulation (PRP) with red and green laser in diabetic patients. Study Design. Randomized clinical trial. Methods. A total of 50 patients with bilateral proliferative diabetic retinopathy and no diabetic macular edema underwent PRP. One eye was randomly assigned to red or green laser. Subfoveal choroidal, central retinal, and RNFL thicknesses were evaluated at baseline and 6 weeks after treatment. Results. The mean subfoveal choroidal, central retinal, and peripapillary nerve fiber layer (RNFL) thickness increased significantly in each eye 6 weeks after PRP (P values in red laser group: <0.01, 0.03, and <0.01, resp., and in green laser group <0.01, <0.01, and <0.01). There was no difference between red and green laser considering subfoveal choroidal, central retinal, and peripapillary nerve fiber layer (RNFL) thickness increase after PRP (P values: 0.184, 0.404, and 0.726, resp.). Conclusion. Both red and green lasers increased mean subfoveal choroidal, central retinal, and peripapillary nerve fiber layer (RNFL) thickness significantly 6 weeks after PRP, but there is no difference between these two modalities in this regard

Removal of subfoveal perfluorocarbon liquid: Report of 3 cases

Purpose: To report removal of retained subfoveal perfluorocarbon liquid (PFCL) after vitrectomy for retinal detachment. Methods: Three patients underwent 3-port 23-gauge vitrectomy in an attempt to remove retained subfoveal PFCL bubble secondary to retinal detachment surgery. In two patients, removal was achieved via a 23-G needle whereas the third patient with multiple small subfoveal droplets, multiple punctures were required and in that case a small 40-G needle was used.We assessed best corrected visual acuity (BCVA), fundus imaging, and spectral domain optical coherence tomography (SD-OCT) of all patients before and after surgery. Results: The subfoveal PFCL was successfully removed in all 3 eyes and although a functional improvement was documented, outer retinal atrophy and photoreceptor loss was observed in all our cases. Conclusions: SD-OCT allows early recognition of retained subfoveal PFCL. Surgical removal may lead to retinal morphologic restoration and functional improvement. While we achieved complete removal of PFCL with both 23-G and 40-G instrumentation, we believe the versatility and ease justifies the universal usage of 40-G retinotomy needles. Keywords: Subfoveal perfluorocarbon, PFCL, PFCL remova