**5. Pathogen detection**

SAW devices have seen applications in biology and medicine in the past. Unfortunately, strong radiation losses are observed for Rayleigh surface waves and most Lamb-mode surface waves. These types of devices have surface displacement for propagation modes have displacements normal on the surface. In liquid environments, we need to use surface waves that have the particle displacement parallel to the device surface and normal to the Love-mode SAW biosensors that have also been developed for the detection of microbial species. A series of devices have been developed by Sandia National Laboratory in collaboration with the University of New Mexico's Health Science Center. Researchers Branch and Brozik at Sandia National Laboratory reported Low-level detection of endospores from *Bacillus Antracis* simulants using a love mode biosensor based on a 36o YX LiTaO3 substrate. When using a polyimide

#### *Development of Simple and Portable Surface Acoustic Wave Biosensors for Applications… DOI: http://dx.doi.org/10.5772/intechopen.106630*

guiding layer, this system was capable of detecting *Bacillus thuringiensis* B8 endospores at a level between 1 and 2 ng/cm2 . Larson and Baca from the University of New Mexico reported the benefits of using a Love-mode SAW device for viral and bacterial detection for clinical applications. **Figure 4** shows unpublished data from measurement of human cardiac troponin complex from serum samples. The values were measured on a lithium tantalate biosensor and coated with monoclonal antibodies from Hytest, Finland, as seen in **Figure 4**. In this report, they disused their findings on SAW devices that were in commercial development. In another report, Bisoffi et al. at the University of New Mexico reported using a Love-mode SAW device to detect a series of different viral particles and viral particles complex solution. In one experiment, the authors compare the detection of solutions containing sewage and other waste material. Bisoffi et al. reported developing the detection of HIV virus type 1 and type 2 using a Love-mode SAW device. In this study, three commonly occurring viral particles were detected from a complex matrix; river and sewage effluent. The SAW sensors were first treated with an organo-silane, 10% 3-glycidyloxypropyl trimethoxysilane (GPTMS), and then functionalized with an antibody. The device allowed multiplexed detection that was specific for HIV-1 and HIV-2 were introduced. The report not only confirm that the SAW could detect viral particles at a level below the standard ELISA and PCR methods but also demonstrated that the Love-mode SAW device could distinguish between HIV type 1 and type 2. Branch and Thayne reported the development of a Love-mode acoustic array biosensor platform that allowed autonomous detection of pathogenic microbes that are critical for human health and safety. Branch and Thayne reported antigen-capture of the targeted pathogens with a mass sensitivity of 7.19 ± 0.74 mm2 /ng with a detection limit of 6.7 ± 0.40 pg./mm2 . In yet another report, Baca et al. report the detection of fragmented *Ebola* antigens at the point of care without the need for added reagents, sample processing, or specialized personnel to run the test. The test could be performed by first responders. The limit of detection for this methodology was below the average level of viremia detected on the first day of symptoms by PCR. Baca and colleagues from the University of New Mexico observed a semi-log sensor response for highly fragmented Ebola viral particles with

#### **Figure 4.**

*The plot of injected mass versus phase shift. This investigation of rapid human cardiac troponin ITC complex (cTn-ITC) detected from human blood, which is an indication of heart muscle damage following a myocardial infarction, using a SAW biosensor. The region in green represents the clinically relevant region.*

a detection limit of 1.9 x 104 PFU/ml. The devices used by both the researchers at Fisk University are fabricated at Sandia National Laboratory and are similar to devices used at the University of New Mexico.
