Functionality and stability of heparin immobilized onto poly(dimethylsiloxane)

A Pumpless Microfluidic Neonatal Lung Assist Device for Support of Preterm Neonates in Respiratory Distress

Premature neonates suffer from respiratory morbidity as their lungs are immature, and current supportive treatment such as mechanical ventilation or extracorporeal membrane oxygenation causes iatrogenic injuries. A non-invasive and biomimetic concept known as the "artificial placenta" (AP) would be beneficial to overcome complications associated with the current respiratory support of preterm infants. Here, a pumpless oxygenator connected to the systemic circulation supports the lung function to relieve respiratory distress. In this paper, the first successful operation of a microfluidic, artificial placenta type neonatal lung assist device (LAD) on a newborn piglet model, which is the closest representation of preterm human infants, is demonstrated. This LAD has high oxygenation capability in both pure oxygen and room air as the sweep gas. The respiratory distress that the newborn piglet is put under during experimentation, repeatedly and over a significant duration of time, is able to be relieved. These findings indicate that this LAD has a potential application as a biomimetic artificial placenta to support the respiratory needs of preterm neonates.

Surface modification on polydimethylsiloxane-based microchannels with fragmented poly(l-lactic acid) nanosheets

Surface modification is a critical issue in various applications of polydimethylsiloxane (PDMS)-based microfluidic devices. Here, we describe a novel method through which PDMS-based microchannels were successfully modified with fragmented poly(l-lactic acid) (PLLA) nanosheets through a simple patchwork technique that exploited the high level of adhesiveness of PLLA nanosheets. Compared with other surface modification methods, our method required neither complicated chemical modifications nor the use of organic solvents that tend to cause PDMS swelling. The experimental results indicated that the modified PDMS exhibited excellent capacity for preventing the adhesion and activation of platelets. This simple yet efficient method can be used to fabricate the special PDMS microfluidic devices for biological, medical, and even hematological purposes.

In vitro evaluation and in vivo demonstration of a biomimetic, hemocompatible, microfluidic artificial lung

Despite the promising potential of microfluidic artificial lungs, current designs suffer from short functional lifetimes due to surface chemistry and blood flow patterns that act to reduce hemocompatibility. Here, we present the first microfluidic artificial lung featuring a hemocompatible surface coating and a biomimetic blood path. The polyethylene-glycol (PEG) coated microfluidic lung exhibited a significantly improved in vitro lifetime compared to uncoated controls as well as consistent and significantly improved gas exchange over the entire testing period. Enabled by our hemocompatible PEG coating, we additionally describe the first extended (3 h) in vivo demonstration of a microfluidic artificial lung.

Determination of the size distribution of blood microparticles directly in plasma using atomic force microscopy and microfluidics

Microparticles, also known as microvesicles, found in blood plasma, urine, and most other body fluids, may serve as valuable biomarkers of diseases such as cardiovascular diseases, systemic inflammatory disease, thrombosis, and cancer. Unfortunately, the detection and quantification of microparticles are hampered by the microscopic size of these particles and their relatively low abundance in blood plasma. The use of a combination of microfluidics and atomic force microscopy to detect microparticles in blood plasma circumvents both problems. In this study, capture of a specific subset of microparticles directly from blood plasma on antibody-coated mica surface is demonstrated. The described method excludes isolation and washing steps to prepare microparticles, improves the detection sensitivity, and yields the size distribution of the captured particles. The majority of the captured particles have a size ranging from 30 to 90 nm, which is in good agreement with prior results obtained with microparticles immediately isolated from fresh plasma. Furthermore, the qualitative shape of the size distribution of microparticles is shown not to be affected by high-speed centrifugation or the use of the microfluidic circuit, demonstrating the relative stable nature of microparticles ex vivo.

Surface modification on polyurethanes by using bioactive carboxymethylated fungal glucan from Poria cocos

In this work, a water-insoluble β-D-glucan (PCSG), isolated from Poria cocos, was carboxymethylated to create a water-soluble derivative named as CP. After free amino groups have been introduced, CP was covalently immobilized onto PU surface. The hydrophilicity and the concentration of carboxyl group on the modified PU surface were determined. The fibrinogen and albumin adsorption to the surface, in vitro blood compatibility, and antibacterial activity of the surface against Pseudomonas aeruginosa were evaluated. The water contact angle measurement indicated that the hydrophilicity of PU surface increased after modification. The fibrinogen adsorption of the modified PU surface decreased 51.5%, compared with control PU. CP immobilization could prolong the blood coagulation time was suggested by APTT experiment. Antibacterial activity experiments indicated that CP modified surface obviously suppressed the growth of P. aeruginosa. Thereby, CP immobilization improves blood compatibility of PU surface and introduces special antibacterial bioactivity.

A Niche for Microfluidics in Portable Hematology Analyzers

The complete blood count (CBC) has by and large remained confined to the traditional laboratory setting since its inception. Used in a variety of diagnostic assessments, the CBC has essentially become limited to clinical laboratories because of reliance on large automated hematology devices. With many potential uses at the point of care and clinical settings, as well as the research laboratory, a portable low-cost hematology analyzer could aid in earlier detection of a wide variety of medical conditions. Using smaller sample volumes, inexpensive polymers, and low power consumption, microfluidic devices present one such route toward miniaturization of the traditional flow cytometer-based hematology analyzers. This review focuses on challenges for development of cost-effective portable analyzers, potential areas for point-of-care clinical usage, current commercial systems with increasing portability, and recent research in improved miniaturization and automation, including developments in acoustic and inertial focusing techniques and novel detection methodologies.

Bioactive heparin immobilized onto microfluidic channels in poly(dimethylsiloxane) results in hydrophilic surface properties

A new composition of heparin coating for microfluidic systems made out of poly(dimethylsiloxane) (PDMS) was developed and evaluated. The coating that consists of a conditioning polyamine layer followed by two heparin/glutaraldehyde layers, resulted in channel surfaces with sufficient wettability to obtain flow of human normal plasma by capillary force alone. Hydrophilic channel walls are a desirable characteristic in microfluidic devices, since alternative pumping mechanisms must otherwise be included into the system. The immobilized heparin showed high antithrombin-binding capacity and a low degree of blood-material interaction. Plasma in contact with heparin-coated PDMS formed no detectable fibrin in a spectrophotometric assay by which plasma in contact with non-treated PDMS showed complete coagulation. The quartz crystal microbalance technique with energy dissipation monitoring (QCM-D) was utilized to obtain detailed information regarding adsorption kinetics and structural properties of the different layers composing the heparin coating.