A Multichannel Microfluidic Sensing Cartridge for Bioanalytical Applications of Monolithic Quartz Crystal Microbalance

Integrating acoustic wave sensors into lab-on-a-chip (LoC) devices is a well-known challenge. We address this challenge by designing a microfluidic device housing a monolithic array of 24 high-fundamental frequency quartz crystal microbalance with dissipation (HFF-QCMD) sensors. The device features six 6-µL channels of four sensors each for low-volume parallel measurements, a sealing mechanism that provides appropriate pressure control while assuring liquid confinement and maintaining good stability, and provides a mechanical, electrical, and thermal interface with the characterization electronics. We validate the device by measuring the response of the HFF-QCMD sensors to the air-to-liquid transition, for which the robust Kanazawa–Gordon–Mason theory exists, and then by studying the adsorption of model bioanalytes (neutravidin and biotinylated albumin). With these experiments, we show how the effects of the protein–surface interactions propagate within adsorbed protein multilayers, offering essentially new insight into the design of affinity-based bioanalytical sensors.

3D-printed Point-of-Care Platform for Genetic Testing of Infectious Diseases Directly in Human Samples Using Acoustic Sensors and a Smartphone

The objective of this work is to develop a methodology and associated platform for nucleic acid detection at the point-of-care (POC) that is sensitive, user-friendly, affordable, rapid, and robust. The heart of this system is an acoustic wave sensor, based on a Surface Acoustic Wave (SAW) or Quartz Crystal Microbalance (QCM) device, which is employed for the label-free detection of isothermally amplified target DNA. Nucleic acids amplification and detection is demonstrated inside three crude human samples, i.e., whole blood, saliva, and nasal swab, spiked in with 10-100 Salmonella cells. To qualify for POC applications, a portable platform was developed based on 3D printing, integrating inside a single box: (i) simple fluidics based on plastic tubing and a mini peristaltic pump, (ii) a heating plate combined with disposable reaction tubes for isothermal amplification; (iii) a mini antenna analyzer operated through a tablet; and (iv) an acoustic wave device housing unit. The simplicity of the method combined with smartphone operation and detection, rapid sample-to-answer analysis time (30 min), and high performance (detection limit 4 × 10³ CFU/ml) in three of the most important human samples in diagnostics suggest that the methodology could become a tool of choice for nucleic acid detection at the POC. In addition, the low cost of the platform and assay holds promise for its adoption in resource limited areas. The acoustic detection method is shown to give similar results with a standard colorimetric assay carried out in saliva and nasal swab but can also be used to detect nucleic acids inside whole blood, where a colorimetric assay failed to perform.