Optofluidic Flow Cytometer with In-Plane Spherical Mirror for Signal Enhancement.

Statistical analysis of the properties of single microparticles, such as cells, bacteria or plastic slivers, has attracted increasing interest in recent years. In this regard, field flow cytometry is considered the gold standard technique, but commercially available instruments are bulky, expensive, and not suitable for use in point-of-care (PoC) testing. Microfluidic flow cytometers, on the other hand, are small, cheap and can be used for on-site analyses. However, in order to detect small particles, they require complex geometries and the aid of external optical components. To overcome these limitations, here, we present an opto-fluidic flow cytometer with an integrated 3D in-plane spherical mirror for enhanced optical signal collection. As a result, the signal-to-noise ratio is increased by a factor of six, enabling the detection of particle sizes down to 1.5 µm. The proposed optofluidic detection scheme enables the simultaneous collection of particle fluorescence and scattering using a single optical fiber, which is crucial to easily distinguishing particle populations with different optical properties. The devices have been fully characterized using fluorescent polystyrene beads of different sizes. As a proof of concept for potential real-world applications, signals from fluorescent HEK cells and Escherichia coli bacteria were analyzed.

Insight on the Intracellular Supramolecular Assembly of DTTO: A Peculiar Example of Cell-Driven Polymorphism.

The assembly of supramolecular structures within living systems is an innovative approach for introducing artificial constructs and developing biomaterials capable of influencing and/or regulating the biological responses of living organisms. By integrating chemical, photophysical, morphological, and structural characterizations, it is shown that the cell-driven assembly of 2,6-diphenyl-3,5-dimethyl-dithieno[3,2-b:2',3'-d]thiophene-4,4-dioxide (DTTO) molecules into fibers results in the formation of a "biologically assisted" polymorphic form, hence the term bio-polymorph. Indeed, X-ray diffraction reveals that cell-grown DTTO fibers present a unique molecular packing leading to specific morphological, optical, and electrical properties. Monitoring the process of fiber formation in cells with time-resolved photoluminescence, it is established that cellular machinery is necessary for fiber production and a non-classical nucleation mechanism for their growth is postulated. These biomaterials may have disruptive applications in the stimulation and sense of living cells, but more crucially, the study of their genesis and properties broadens the understanding of life beyond the native components of cells.