Cross-linked chitosan biofunctionalized paper-based microfluidic device towards long term stabilization of blood typing antibodies.

Long term stability of antibodies at room temperature is a major challenge in the commercialization of point-of-care devices for diagnostics. Since chitosan has been proven to be an excellent biofunctionalization material, the effects of four different biofunctionalization processes were studied to improve the room temperature stability of antibodies immobilized on chitosan modified paper-based microfluidic devices using blood typing antibodies as candidates. The devices used in this work have a flower-shaped design with 4 test zones at each corner. In three zones Anti-A, Anti-B, and Anti-D (Anti-Rh) antibodies are immobilized and the fouth zone represents the control (no antibodies) after biofunctionalization. The biofunctionalization of the paper devices was done with chitosan and chitosan cross-linked with sodium triphosphate pentabasic, glutaraldehyde, and sodium hydroxide. These devices were used for blood typing assays using real blood samples. A similar assay was also performed on unmodified (non-biofunctionalized) paper devices for comparison. Chitosan based biofunctionalized paper-devices showed better stability, up to 100 days as compared to 14 days on unmodified paper, at room temperature. Such biofunctionalized paper-based devices will be suitable for on-field and remote testing without any technical expertise and requirement for the cold chain.

Surface-Engineered Paper Hanging Drop Chip for 3D Spheroid Culture and Analysis.

Protein corona coated onto the hydrophilic cellulose fiber turns into hydrophobic upon UV irradiation without hindering the porosity of the paper while simultaneously reducing nonspecific adsorption. Taking advantage of the biofouling-resistant, hydrophobic, and fluid transport through property, we demonstrated hanging drop three-dimensional (3D) spheroid culture and in-site analysis, including drug testing, time-dependent detection of secreted protein, and fluorescence staining without disturbing the spheroids. This single hanging drop system can also be extended to a networked hanging drop chip to mimic in vivo microphysiology by combining with wax-patterned microfluidic channels, where well-to-well interaction can be accurately controlled in a passive manner. As a proof of concept, the effects of a concentration gradient of nutrient and variable dosage of anticancer drugs were studied in the 3D spheroids cultured on paper. The experimental results suggested that a complex network device could be fabricated on a large scale on demand at a minimal cost for 3D spheroid culture. Our method demonstrates a future possibility for paper as a low cost, high-throughput 3D spheroid-based "body-on-a-chip" platform material.

Cloaked Exosomes: Biocompatible, Durable, and Degradable Encapsulation.

Exosomes-nanosized extracellular vesicles (EVs) naturally secreted from cells-have emerged as promising biomarkers and potential therapeutic vehicles, but methods to manipulate them for engineering purposes remain elusive. Among the technical obstacles are the small size and surface complexity of exosomes and the complex processing steps required, which reduce the biocompatibility of currently available methods. The encapsulation of exosomes with a nanofilm of supramolecular complexes of ferric ions (Fe3+ ) and tannic acid is demonstrated here. The resulting natural polyphenol, ≈10 nm thick, protects exosomes from external aggressors such as UV-C irradiation or heat and is controllably degraded on demand. Furthermore, gold nanoparticles can be covalently attached for single-exosome level visualization. To fully exploit their therapeutic potential, chemotherapeutic drug-loaded EVs are functionalized to achieve the targeted, selective killing of cancer cells preferentially over normal cells. This nanofilm not only preserves the native size and chemical makeup of the intrinsic exosomes, but also confers new capabilities for efficient tumor targeting and pH-controlled release of drugs. Demonstrating a scalable method to produce biocompatible, durable, on-demand degradable, and chemically controllable shields for exosome modification and functionalization, the methods introduced here are expected to bring the potential of exosome-based nanomedicine applications closer to reality.

Challenges and Opportunities of Centrifugal Microfluidics for Extreme Point-of-Care Testing.

The advantages offered by centrifugal microfluidic systems have encouraged its rapid adaptation in the fields of in vitro diagnostics, clinical chemistry, immunoassays, and nucleic acid tests. Centrifugal microfluidic devices are currently used in both clinical and point-of-care settings. Recent studies have shown that this new diagnostic platform could be potentially used in extreme point-of-care settings like remote villages in the Indian subcontinent and in Africa. Several technological inventions have decentralized diagnostics in developing countries; however, very few microfluidic technologies have been successful in meeting the demand. By identifying the finest difference between the point-of-care testing and extreme point-of-care infrastructure, this review captures the evolving diagnostic needs of developing countries paired with infrastructural challenges with technological hurdles to healthcare delivery in extreme point-of-care settings. In particular, the requirements for making centrifugal diagnostic devices viable in developing countries are discussed based on a detailed analysis of the demands in different clinical settings including the distinctive needs of extreme point-of-care settings.