Prognostic Factors in Patients with Persistent Full-Thickness Idiopathic Macular Holes Treated with Re-Vitrectomy with Autologous Platelet Concentrate

Purpose: To identify the predictors for anatomical and functional outcome after re-vitrectomy with application of autologous platelet concentrate (APC) in eyes with persistent idiopathic macular hole (MH). Methods: Retrospective study of 103 eyes with persistent MHs after vitrectomy with peeling of internal limiting membrane (ILM) and expansive gas. All patients underwent re-vitrectomy with APC and endotamponade. The anatomical MH closure rate and postoperative best-corrected visual acuity (BCVA) were evaluated. Further, predictive factors influencing the success of the surgery were analyzed. Results: Median BCVA (logMAR) before the surgery was 1.00 (interquartile range [IQR] 0.80–1.30) and the median of minimum diameter between hole edges was 508 μm (IQR 387–631). The final closure rate after re-vitrectomy with APC was 60.2% (62 of 103 eyes). The following predictors were identified to significantly influence the closure rate: tractional hole index (THI), axial length, time between first and second surgery, and the experience of the surgeon (p < 0.05). Conclusions: Re-vitrectomy with APC led to the closure of 60.2% of the persistent MHs. The closure rate negatively correlates with increasing axial length, time between the first and second surgery, and the decreased THI. Further, experienced surgeons (with a history of > 100 pars plana vitrectomies with ILM peeling) had significantly higher closure rates

Digital microfluidic platforms for automated chemical reactions

Microfluidic technology allows the miniaturisation and automation of chemical and biological processes. Specific advantages include the ease of process automation and integration, high analytical throughput, reduced sample and power consumption, increased speed and efficiency of reactions and system portability. Droplet-based microfluidics can be broadly categorised into 'conventional' channel devices or digital microfluidic (DMF) devices. The latter are also known as electrowetting-on-dielectric (EWOD) devices. Both platforms have distinct characteristics, with specific advantages and disadvantages when applied to chemical or biological analysis. High-throughput droplet manipulation is easily achieved with channel microfluidic devices, but it is hard to access individual droplets in this format. On the other hand, DM devices are designed for the manipulation of individual droplets in low-throughput. The bulk of the work in this thesis focuses on developing a complete platform for droplet manipulation using digital microfluidics. Extensive experimentation was undertaken to determine all relevant components of the device, including the composition of the dielectric layer, electrodes and hydrophobic layer. Once the optimum device had been constructed and tested, full automation of device function and droplet manipulation was achieved. Characterisation of on-chip droplet operations was subsequently performed. Special attention was given to droplet 'dispensing' and 'splitting'. Once the fabricated DMF devices had been fully characterised, three proof of principle experiments were developed to investigate the capabilities of DMF devices. To this aim, first a fluorescent dilution series was performed and characterised on-chip, second a peptide bond formation experiment was performed, and finally, iron oxide nanoparticle synthesis was performed on-chip. The integration of DMF devices with a miniaturised spectrometer was used to provide an on-line detection system. Channel microfluidic devices were also investigated with respect to the high-through-put creation of droplet interface bilayers (DIBs). Aqueous droplets containing lipids were formed in an oil carrier medium. As droplets were brought together a lipid bilayer was formed at the interface, creating an artificial membrane. This approach can be used as a platform technology to study trans-membrane proteins and drug-membrane interactions. Although there has been a lot of interest in this area, previous work has focused on the low-throughput formation of DIBs. The method developed here enables the formation of DIBs at rates in excess of 1 DIB per second.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Droplet dispensing in digital microfluidic devices: Assessment of long-term reproducibility

We report an in-depth study of the long-term reproducibility and reliability of droplet dispensing in digital microfluidic devices (DMF). This involved dispensing droplets from a reservoir, measuring the volume of both the droplet and the reservoir droplet and then returning the daughter droplet to the original reservoir. The repetition of this process over the course of several hundred iterations offers, for the first time, a long-term view of droplet dispensing in DMF devices. Results indicate that the ratio between the spacer thickness and the electrode size influences the reliability of droplet dispensing. In addition, when the separation between the plates is large, the volume of the reservoir greatly affects the reproducibility in the volume of the dispensed droplets, creating “reliability regimes.” We conclude that droplet dispensing exhibits superior reliability as inter-plate device spacing is decreased, and the daughter droplet volume is most consistent when the reservoir volume matches that of the reservoir electrode

A microfluidic approach for high-throughput droplet interface bilayer (DIB) formation

We present a simple, automated method for high-throughput formation of droplet interface bilayers (DIBs) in a microfluidic device. We can form complex DIB networks that are able to fill predefined three dimensional architectures. Moreover, we demonstrate the flexibility of the system by using a variety of lipids including 1,2-diphytanoyl-sn-glycero-3-phosphocholine (DPhPC) and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC)

Prognostic Factors in Patients with Persistent Full-Thickness Idiopathic Macular Holes Treated with Re-Vitrectomy with Autologous Platelet Concentrate

Purpose: To identify the predictors for anatomical and functional outcome after re-vitrectomy with application of autologous platelet concentrate (APC) in eyes with persistent idiopathic macular hole (MH). Methods: Retrospective study of 103 eyes with persistent MHs after vitrectomy with peeling of internal limiting membrane (ILM) and expansive gas. All patients underwent re-vitrectomy with APC and endotamponade. The anatomical MH closure rate and postoperative best-corrected visual acuity (BCVA) were evaluated. Further, predictive factors influencing the success of the surgery were analyzed. Results: Median BCVA (logMAR) before the surgery was 1.00 (interquartile range [IQR] 0.80–1.30) and the median of minimum diameter between hole edges was 508 μm (IQR 387–631). The final closure rate after re-vitrectomy with APC was 60.2% (62 of 103 eyes). The following predictors were identified to significantly influence the closure rate: tractional hole index (THI), axial length, time between first and second surgery, and the experience of the surgeon (p < 0.05). Conclusions: Re-vitrectomy with APC led to the closure of 60.2% of the persistent MHs. The closure rate negatively correlates with increasing axial length, time between the first and second surgery, and the decreased THI. Further, experienced surgeons (with a history of > 100 pars plana vitrectomies with ILM peeling) had significantly higher closure rates

Prognostic Factors in Patients with Persistent Full-Thickness Idiopathic Macular Holes Treated with Re-Vitrectomy with Autologous Platelet Concentrate

Purpose: To identify the predictors for anatomical and functional outcome after re-vitrectomy with application of autologous platelet concentrate (APC) in eyes with persistent idiopathic macular hole (MH). Methods: Retrospective study of 103 eyes with persistent MHs after vitrectomy with peeling of internal limiting membrane (ILM) and expansive gas. All patients underwent re-vitrectomy with APC and endotamponade. The anatomical MH closure rate and postoperative best-corrected visual acuity (BCVA) were evaluated. Further, predictive factors influencing the success of the surgery were analyzed. Results: Median BCVA (logMAR) before the surgery was 1.00 (interquartile range [IQR] 0.80–1.30) and the median of minimum diameter between hole edges was 508 μm (IQR 387–631). The final closure rate after re-vitrectomy with APC was 60.2% (62 of 103 eyes). The following predictors were identified to significantly influence the closure rate: tractional hole index (THI), axial length, time between first and second surgery, and the experience of the surgeon (p < 0.05). Conclusions: Re-vitrectomy with APC led to the closure of 60.2% of the persistent MHs. The closure rate negatively correlates with increasing axial length, time between the first and second surgery, and the decreased THI. Further, experienced surgeons (with a history of > 100 pars plana vitrectomies with ILM peeling) had significantly higher closure rates

A droplet-based microfluidic platform for high-throughput, multi-parameter screening of photosensitizer activity

We present a fully integrated droplet-based microfluidic platform for the high-throughput assessment of photodynamic therapy photosensitizer (PDT) efficacy on Escherichia coli. The described platform is able to controllably encapsulate cells and photosensitizer within pL-volume droplets, incubate the droplets over the course of several days, add predetermined concentrations of viability assay agents, expose droplets to varying doses of electromagnetic radiation, and detect both live and dead cells online to score cell viability. The viability of cells after encapsulation and incubation is assessed in a direct fashion, and the viability scoring method is compared to model live/dead systems for calibration. Final results are validated against conventional colony forming unit assays. In addition, we show that the platform can be used to perform concurrent measurements of light and dark toxicity of the PDT agents and that the platform allows simultaneous measurement of experimental parameters that include dark toxicity, photosensitizer concentration, light dose, and oxygenation levels for the development and testing of PDT agent