Micro-lithography on paper, surface process modifications for biomedical performance enhancement

Controllable self-cleaning FET self-assembled RNA-cleaving DNAzyme based DNA nanotree for culture-free Staphylococcus aureus detection

Staphylococcus aureus (SA) poses a serious risk to human and animal health, necessitating a low-cost and high-performance analytical platform for point-of-care diagnostics. Cellulose paper-based field-effect transistors (FETs) with RNA-cleaving DNAzymes (RCDs) can fulfill the low-cost requirements, however, its high hydrophilicity and lipophilicity hinder biochemical modification and result in low sensitivity, poor mechanical stability and poor fouling performance. Herein, we proposed a controllable self-cleaning FET to simplify biochemical modification and improve mechanical stability and antifouling performance. Then, we constructed an RCD-based DNA nanotree to significantly enhance the sensitivity for SA detection. For controllable self-cleaning FET, 1 H,1 H,2 H,2 H-perfluorodecyltrimethoxysilane based-polymeric nanoparticles were synthesized to decorate cellulose paper and whole carbon nanofilm wires. O2 plasma was applied to regulate to reduce fluorocarbon chain density, and then control the hydrophobic-oleophobic property in sensitive areas. Because negatively charged DNA affected the sensitivity of semiconducting FETs, three Y-shaped branches with low-cost were designed and applied to synthesize an RCD-based DNA-Nanotree based on similar DNA-origami technology, which further improved the sensitivity. The trunk of DNA-Nanotree was composed of RCD, and the canopy was self-assembled using multiple Y-shaped branches. The controllable self-cleaning FET biosensor was applied for SA detection without cultivation, which had a wide linear range from 1 to 105 CFU/mL and could detect a low value of 1 CFU/mL.

Nitrite enhanced detection from saliva by simple geometrical modifications of paper-based micromixers

Dysregulation of nitric oxide (NO) and it's two relatively stable metabolites, nitrite, and nitrate, in SARS-CoV-2, are reported in infected populations, especially for nitrates levels > 68.4 μmol/L. In this paper, we measure the abnormal presence of nitrite in the saliva by developing a cheap μPAD for colorimetric detection through the modified Griess reaction. This includes a diazotization reaction between nitrite and Griess reagent, including Sulfanilamide and N-Naphthyl-ethylenediamine in an acidic medium, causing a pink Azo compound. The modifications are suggested by a numerical method model that couples the mass flux with the porosity medium equations (convection, diffusion and, dispersion) that improves the mixing process. The mixing index was quantified from the concentration deviation method via simulation of a homogeneous two-phase flow in a porous environment. Five μPAD designs were fabricated to verify the simulation results of mixing enhancement on the Griess reactants in saliva samples. The investigated geometries include straight, helical, zig-zag, square wave, and inclined jagged shapes fabricated by direct laser writing, suitable for low cost, mass fabrication. Inclined jagged micromixer exhibited the best performance with up to 40% improvement compared with the simple straight geometry. Deliberate geometrical modifications, exemplified here in a jagged micromixer on paper, cut the limit of detection (LOD) by at least half without impacting the linear detection range.

Plant-Based Structures as an Opportunity to Engineer Optical Functions in Next-Generation Light Management

This review addresses the reconstruction of structural plant components (cellulose, lignin, and hemicelluloses) into materials displaying advanced optical properties. The strategies to isolate the main building blocks are discussed, and the effects of fibrillation, fibril alignment, densification, self-assembly, surface-patterning, and compositing are presented considering their role in engineering optical performance. Then, key elements that enable lignocellulosic to be translated into materials that present optical functionality, such as transparency, haze, reflectance, UV-blocking, luminescence, and structural colors, are described. Mapping the optical landscape that is accessible from lignocellulosics is shown as an essential step toward their utilization in smart devices. Advanced materials built from sustainable resources, including those obtained from industrial or agricultural side streams, demonstrate enormous promise in optoelectronics due to their potentially lower cost, while meeting or even exceeding current demands in performance. The requirements are summarized for the production and application of plant-based optically functional materials in different smart material applications and the review is concluded with a perspective about this active field of knowledge.

Determination of total protein content in biomedical products by the PDMS-assisted lab-in-a-syringe assay using 3D printed scaffolds removal

The aim of our work was to develop a low-cost, portable device for the fast and easy determination of total protein content by using PDMS-based lab-in-a-syringe technology with removal of 3D-printed channels. We proposed two designs with a one-step PDMS curing and a two-step PDMS-curing fabrication procedure. The one-step PDMS microdevices were found to be the best in the view of preparation, repeatability, and stability of the reagent. This design was then applied for the determination of total protein content in biomedical products using the Bradford assay.

Micro and Nanoscale Technologies for Diagnosis of Viral Infections

Viral infection is one of the leading causes of mortality worldwide. The growth of globalization significantly increases the risk of virus spreading, making it a global threat to future public health. In particular, the ongoing coronavirus disease 2019 (COVID-19) pandemic outbreak emphasizes the importance of devices and methods for rapid, sensitive, and cost-effective diagnosis of viral infections in the early stages by which their quick and global spread can be controlled. Micro and nanoscale technologies have attracted tremendous attention in recent years for a variety of medical and biological applications, especially in developing diagnostic platforms for rapid and accurate detection of viral diseases. This review addresses advances of microneedles, microchip-based integrated platforms, and nano- and microparticles for sampling, sample processing, enrichment, amplification, and detection of viral particles and antigens related to the diagnosis of viral diseases. Additionally, methods for the fabrication of microchip-based devices and commercially used devices are described. Finally, challenges and prospects on the development of micro and nanotechnologies for the early diagnosis of viral diseases are highlighted.

Predicting Dimensions in Microfluidic Paper Based Analytical Devices

The main problem for the expansion of the use of microfluidic paper-based analytical devices and, thus, their mass production is their inherent lack of fluid flow control due to its uncontrolled fabrication protocols. To address this issue, the first step is the generation of uniform and reliable microfluidic channels. The most common paper microfluidic fabrication method is wax printing, which consists of two parts, printing and heating, where heating is a critical step for the fabrication of reproducible device dimensions. In order to bring paper-based devices to success, it is essential to optimize the fabrication process in order to always get a reproducible device. Therefore, the optimization of the heating process and the analysis of the parameters that could affect the final dimensions of the device, such as its shape, the width of the wax barrier and the internal area of the device, were performed. Moreover, we present a method to predict reproducible devices with controlled working areas in a simple manner.

Micro-fabrication by wax spraying for rapid smartphone-based quantification of bio-markers

A cheap/rapid technique for the fabrication of μPADs is presented for point of care analysis. Hydrophobic channels were formed across the width of the paper by spraying hot pure wax. This biocompatible novel process yielded uniform 300 ± 5 μm hydrophilic microchannels on paper, without the use of the cleanroom, UV lamp, or organic solvents and was completed in a single step without the need for a hotplate. Hot wax is properly impregnated across paper thickness by spraying under optimized temperature and pressure. Our method is advantageous in the cost and ease of fabrication, process time (<1 min), the feasibility of mass-fabrication, readout, environmental considerations and multiplexing due to the embossed structure of remnant wax. The performance of the resulting μPAD was assessed on a multiplexed Uric acid and Nitride assay, bearing 95% of confidence level in the readout against standardized tests. A novel RGB processing app was developed for smart-phones to quantify colorimetric read-outs through a heuristic normalization equation that converts RGB to integer systems. This combinatorial sensor demonstrates a good linear range (up to 800 μM for Uric acid and 1250 μM for Nitride), low detection limit (100 μM for uric acid and 156 μM for nitride).