This report describes the fabrication of a low-cost magnetic separator holder combining 3D printing and compact neodymium blocks for allowing magnetic extraction and purification of RNA from samples collected by nasopharyngeal swab from patients infected by SARS-CoV-2. The device was designed to contain 24 entrances for plastic microtubes in an arrangement like a commercial device. The proof of concept of the proposed device was successfully demonstrated through the sample extraction and purification of swab samples collected from eight patients suspected of SARS-CoV-2 infection. The sample preparation protocol was performed using a commercial kit containing magnetic beads and different solutions. The performance of the printed device was compared to a commercial magnetic separator, usually employed in the golden standard techniques. The fabrication of the 3D printed magnetic separator was completed under optimized printing conditions within 6 h at cost of 4 USD per unit. The RNA extracted from samples using both devices was analyzed by reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) and the achieved results have indicated no statistical different at confidence level of 95%. Based on the achievements, the use of 3D printing and neodymium blocks have demonstrated an alternative route to be used in routing analysis associated to COVID-19 diagnosis.

This report describes a rapid and inexpensive colorimetric method based on biuret assay for total serum protein analysis using wax printed microzone plates and a desktop scanner. The colorimetric assay was performed in 96-microzone plates fabricated on polyester films through a wax printing protocol. The image scanning mode and the concentration of the biuret reagents were optimized to achieve the highest detectability levels. The best analytical response was obtained using the slide scanning mode as well as 4% CuSO4 and 150 mmol L-1 potassium sodium tartrate solutions. The proposed method offered linear relationship for the bovine serum albumin concentration range between 25 and 200 µmol L-1 with a limit of detection of 9.7 µmol L-1. The colorimetric approach revealed satisfactory precision (relative standard deviation values between 0.6 and 4.4%). The bioanalytical feasibility was demonstrated through the total protein analysis in serum samples collected from dogs previously diagnosed with kidney disease. The total serum protein concentrations varied from 960 ± 19 to 1661 ± 38 µmol L-1 and the achieved values revealed good accordance with those obtained through a reference method. Based on the reported results, wax printed microzone plates have demonstrated simplicity and potential to be adopted as alternative platforms for bioassays.

Electrophoresis is by far the most popular separation method implemented in microscale, most probably due to its instrumental simplicity, low cost and portability. Due to the increasing use of miniaturized electrophoretic systems, the study of fundamental aspects can improve the development of methodologies for several applications. One of the major challenges related to electrophoresis chips refers to the sample injection mode, in this way, this study presents a review on sample injection methods for microchip electrophoresis covering electrokinetic and hydrodynamic approaches, describing theoretic and instrumental aspects. Since the sample volume affects the analytical performance, the precise and reproducible control of the sample amount to be introduced into the separation channel is highly desirable to ensure reliable chemical analysis. Electrokinetic modes based on floating, pinched and gated protocols are presented and discussed providing an overview about the electrokinetic control of the sample through three methodologies. In the same way, hydrodynamic techniques including the use of microfabricated valves and pumps, syringe pumps, electronic micropipettes, rubber suction bulb and acupuncture needle are approached, thus expanding the view of hydrodynamic injectors based on classical and alternative methods.

This report describes the use of toner-based microzone plates for quantitative determination of glucose in artificial urine and human serum samples using colorimetric detection. The proposed approach has exhibited a linear response for glucose concentration levels from 0 to 10 mmol L-1 with determination coefficient (R2) of 0.996. The achieved values for sensitivity and limit of detection were 5.1 AU (mmol L-1)-1 and 0.6 mmol L-1, respectively. The glucose analysis in artificial serum samples revealed error lower than 5% in comparison with certified values provided by the supplier. Lastly, the proposed approach has also provided suitable accuracy (92-105%) for glucose measurements in artificial urine samples.