Low-Level Light Therapy in Association with Intense Pulsed Light for Meibomian Gland Dysfunction.

Purpose: To study the clinical benefit of low-level light therapy when associated with intense pulsed light for the treatment of meibomian gland dysfunction. Methods: An observational study. Two groups of patients that were treated with IPL were considered: group 1 (31 subjects, 62 eyes), intense pulsed light followed by low-level light therapy and group 2 (31 subjects, 62 eyes) intense pulsed light alone. In both groups, treatments were performed in 3 sessions and subjects were evaluated at baseline and 3 weeks after the last treatment session. Values are shown as mean difference ± standard deviation. Results: We observed a significant improvement in OSDI-12 score and lipid layer thickness, in both groups (-22.7±17.5, p<0.001 in group 1 and -23.6±23.8, p<0.001 in group 2 for OSDI and +18.6 ± 37.0, p<0.001 in group 1 and +19.9 ± 26.4, p<0.001 in group 2 for lipid layer thickness). Despite no differences between groups at baseline (p=0.469), only group 1 had a significant improvement in Schirmer test (+1.6±4.8, p=0.009 in group 1 and +1.7±6.9, p=0.057 in group 2). No significant side effects were noted. No patient in any group felt subjectively "worse" after the treatment. Conclusion: Intense pulsed light seems effective and safe for the treatment of meibomian gland dysfunction, improving symptoms and the tear film lipid layer. This study shows no strong evidence of the benefit of low-level light therapy, but it shows weak evidence that it may further improve aqueous tear production.

PtOEP-PDMS-Based Optical Oxygen Sensor.

The advanced and widespread use of microfluidic devices, which are usually fabricated in polydimethylsiloxane (PDMS), requires the integration of many sensors, always compatible with microfluidic fabrication processes. Moreover, current limitations of the existing optical and electrochemical oxygen sensors regarding long-term stability due to sensor degradation, biofouling, fabrication processes and cost have led to the development of new approaches. Thus, this manuscript reports the development, fabrication and characterization of a low-cost and highly sensitive dissolved oxygen optical sensor based on a membrane of PDMS doped with platinum octaethylporphyrin (PtOEP) film, fabricated using standard microfluidic materials and processes. The excellent mechanical and chemical properties (high permeability to oxygen, anti-biofouling characteristics) of PDMS result in membranes with superior sensitivity compared with other matrix materials. The wide use of PtOEP in sensing applications, due to its advantage of being easily synthesized using microtechnologies, its strong phosphorescence at room temperature with a quantum yield close to 50%, its excellent Strokes Shift as well as its relatively long lifetime (75 µs), provide the suitable conditions for the development of a miniaturized luminescence optical oxygen sensor allowing long-term applications. The influence of the PDMS film thickness (0.1-2.5 mm) and the PtOEP concentration (363, 545, 727 ppm) in luminescent properties are presented. This enables to achieve low detection levels in a gas media range from 0.5% up to 20%, and in liquid media from 0.5 mg/L up to 3.3 mg/L at 1 atm, 25 °C. As a result, we propose a simple and cost-effective system based on a LED membrane photodiode system to detect low oxygen concentrations for in situ applications.

Portable Device for Optical Quantification of Hemozoin in Diluted Blood Samples.

OBJECTIVE: This paper focuses on a novel and portable device prototype with optical detectors to quickly and efficiently detect hemozoin (Hz) in blood, aiming at malaria diagnostics. METHODS: Taking advantage of the particular features of malaria parasite in infected blood, particularly the Hz formation, the main innovation described is a portable device for the optical quantification of parasitic Hz in blood, through optical absorbance spectrophotometry. This device comprises detection chambers for fluidic samples, an optical emission and detection system, and a power supply system to provide autonomy. The working principle is based on colorimetric detection, by absorbance, at six specific wavelengths. A detection algorithm relates the absorbance values at all wavelengths to quantify the Hz concentration, thus working as a biomarker of malaria presence and stage. RESULTS: Under the tested conditions, e.g., in fluidic samples containing synthetic Hz, hemoglobin, and diluted whole blood, the device detected Hz above 1 µg/mL concentrations with 100% sensitivity and 96.3% specificity. CONCLUSION: This paper features an autonomous, portable, 1-min analysis time, and low-cost per test device, without the need for samples, centrifugation, allowing the use of whole blood. SIGNIFICANCE: The presented device is a step ahead for meeting the growing clinical demands for reliable, rapid, portable, and quantitative malaria diagnosis.

Multilayered membranes with tuned well arrays to be used as regenerative patches.

Membranes have been explored as patches in tissue repair and regeneration, most of them presenting a flat geometry or a patterned texture at the nano/micrometer scale. Herein, a new concept of a flexible membrane featuring well arrays forming pore-like environments to accommodate cell culture is proposed. The processing of such membranes using polysaccharides is based on the production of multilayers using the layer-by-layer methodology over a patterned PDMS substrate. The detached multilayered membrane exhibits a layer of open pores at one side and a total thickness of 38±2.2µm. The photolithography technology used to produce the molds allows obtaining wells on the final membranes with a tuned shape and micro-scale precision. The influence of post-processing procedures over chitosan/alginate films with 100 double layers, including crosslinking with genipin or fibronectin immobilization, on the adhesion and proliferation of human osteoblast-like cells is also investigated. The results suggest that the presence of patterned wells affects positively cell adhesion, morphology and proliferation. In particular, it is seen that cells colonized preferentially the well regions. The geometrical features with micro to sub-millimeter patterned wells, together with the nano-scale organization of the polymeric components along the thickness of the film will allow to engineer highly versatile multilayered membranes exhibiting a pore-like microstructure in just one of the sides, that could be adaptable in the regeneration of multiple tissues. STATEMENT OF SIGNIFICANCE: Flexible multilayered membranes containing multiple micro-reservoirs are found as potential regenerative patches. Layer-by-layer (LbL) methodology over a featured PDMS substrate is used to produce patterned membranes, composed only by natural-based polymers, that can be easily detached from the PDMS substrate. The combination of nano-scale control of the polymeric organization along the thickness of the chitosan/alginate (CHT/ALG) membranes, provided by LbL, together with the geometrical micro-scale features of the patterned membranes offers a uniqueness system that allows cells to colonize 3-dimensionally. This study provides a promising strategy to control cellular spatial organization that can face the region of the tissue to regenerate.

A numerical and experimental study of acoustic micromixing in 3D microchannels for lab-on-a-chip devices.

This paper reports a numerical and experimental study of acoustic streaming and micromixing in polydimethylsiloxane microchannels. The mixing between two fluids flowing in microchannels was evaluated through the following conditions: (1) using a 28 µm thick ß-poly(vinylidene fluoride) (ß-PVDF) as a piezoelectric transducer actuated with a 24 Vpp and 40 MHz sinusoidal voltage; (2) using different flow rates. The results suggest that the mixing length increases as the flow rate increases and that the acoustic streaming phenomenon leads to a reduction on the mixing length. The good qualitative agreement between numerical and experimental results is a valuable indicator to predict the mixing performance of microfluidic devices, for improving biological fluid analysis in diagnosis lab-on-a-chip devices.