Paper-based genetic assays with bioconjugated gold nanorods and an automated readout pipeline.

Paper-based biosensors featuring immunoconjugated gold nanoparticles have gained extraordinary momentum in recent times as the platform of choice in key cases of field applications, including the so-called rapid antigen tests for SARS-CoV-2. Here, we propose a revision of this format, one that may leverage on the most recent advances in materials science and data processing. In particular, we target an amplifiable DNA rather than a protein analyte, and we replace gold nanospheres with anisotropic nanorods, which are intrinsically brighter by a factor of ~ 10, and multiplexable. By comparison with a gold-standard method for dot-blot readout with digoxigenin, we show that gold nanorods entail much faster and easier processing, at the cost of a higher limit of detection (from below 1 to 10 ppm in the case of plasmid DNA containing a target transgene, in our current setup). In addition, we test a complete workflow to acquire and process photographs of dot-blot membranes with custom-made hardware and regression tools, as a strategy to gain more analytical sensitivity and potential for quantification. A leave-one-out approach for training and validation with as few as 36 sample instances already improves the limit of detection reached by the naked eye by a factor around 2. Taken together, we conjecture that the synergistic combination of new materials and innovative tools for data processing may bring the analytical sensitivity of paper-based biosensors to approach the level of lab-grade molecular tests.

In situ diode laser fenestration: An ex-vivo evaluation of irradiation effects on human aortic tissue.

The in situ laser fenestration is an interesting option for the endovascular treatment of short-necked aneurysms with an intraoperative modification of a standard endograft. According to literature evidence, diode laser emitting in the near-infrared wavelength (810 nm) can be successfully used to fenestrate the endograft fabric. This paper describes a three-dimensional navigation system for the accurate targeting of the fenestration site, then reports results of an ex vivo study to assess whether the laser operative conditions, which ensure the fabric fenestration, are harmless for the biological tissue surrounding the endoprosthesis. Two hundred twenty-five samples of human aorta, including healthy specimens and abdominal aortic aneurysm samples, were irradiated ex vivo using a 810 nm diode laser. Energy and pulse duration were varied. Irradiated tissues were fixed in formaldehyde, sectioned and subjected to histological examination. Only 7.5% of the irradiated samples exhibited a thermal damage, which was always confined to the contact point between the laser fiber tip and the aortic wall. These experiments suggest that the diode laser can be safely used for the proposed surgical application.

Polarization-dependent deformation in light responsive polymers doped by dichroic dyes.

Light represents a very versatile stimulus and its use to control the deformation in shape-changing polymers can take advantage of multiple parameters (such as wavelength, intensity and polarization) to be explored in order to obtain differentiated responses. Polymers with selected color responsiveness are commonly prepared by using different dyes, while a polarization-dependent control can be introduced exploiting trans-cis isomerization of azobenzenes. As shape-changing polymers driven by a photothermal effect are gaining more and more attention in many application fields, exploring polarization to modulate their response could enlarge the tuning parameter space and provide an insight into the material optical properties. In this work, we demonstrate the effect of light polarization on the deformation of liquid crystalline networks doped by a small amount of a push-pull azobenzene. We demonstrate how enhancing the dye alignment in the polymeric matrix leads to different deformations by orthogonal polarizations. These results demonstrate polarization as a convenient further degree of freedom besides wavelength and intensity of the light stimulus.

A multifunctional organosilica cross-linker for the bio-conjugation of gold nanorods.

We report on the use of organosilica shells to couple gold nanorods to functional peptides and modulate their physiochemical and biological profiles. In particular, we focus on the case of cell penetrating peptides, which are used to load tumor-tropic macrophages and implement an innovative drug delivery system for photothermal and photoacoustic applications. The presence of organosilica exerts subtle effects on multiple parameters of the particles, including their size, shape, electrokinetic potential, photostability, kinetics of endocytic uptake and cytotoxicity, which are investigated by the interplay of colorimetric methods and digital holographic microscopy. As a rule of thumb, as the thickness of organosilica increases from none to ∼30nm, we find an improvement of the photophysical performances at the expense of a deterioration of the biological parameters. Therefore, detailed engineering of the particles for a certain application will require a careful trade-off between photophysical and biological specifications.