Current development of saliva/oral fluid-based diagnostics

Abstract

Saliva can be easily obtained in medical and non-medical settings, and contains numerous bio-molecules, including those typically found in serum for disease detection and monitoring. In the past two decades, the achievements of high-throughput approaches afforded by biotechnology and nanotechnology allow for disease-specific salivary biomarker discovery and establishment of rapid, multiplex, and miniaturized analytical assays. These developments have dramatically advanced saliva-based diagnostics. In this review, we discuss the current consensus on development of saliva/oral fluid-based diagnostics and provide a summary of recent research advancements of the Texas-Kentucky Saliva Diagnostics Consortium. In the foreseeable future, current research on saliva based diagnostic methods could revolutionize health care.

Figure 1. Microbead-based reactor systems

Agarose microbeads that serve as single enzyme-linked immunosorbent assay (ELISA) reactor sensors (a) are arrayed in microchips (b) assembled into a disposable microfludic cassette that can be inserted into an analyzer (d) for automated assay execution and processing of image data acquired within this optical sensor (Modified from Jokerst et al. Nanomedicine, 2010 ).

Figure 2. Saliva AMI testing in ambulance

(a) 12 lead EKG used by paramedics to transmit initial findings to emergency room physicians (left). The portable saliva-based diagnostics NBC platform can complement EKG for the identification of AMI cases. (b) Logistic regression and ROC analysis using serum and salivary biomarkers in conjunction with EKG exhibited improvement of diagnosis of AMI. The EKG and AMI biomarkers of 42 healthy controls, 46 AMI (23 NSTEMI and 23 STEMI) are measured and compared. In serum, the ROC curve was improved from 0.81 to 0.92 in triage biomarkers (cTnI, myoglobin and CK-MB) were used as diagnostic indexes (left). However, the combined use of salivary CRP and MPO in conjunction with EKG (right), produced an excellent ROC 0.94 (i.e., >90% specificity and sensitivity of AMI diagnosis). (c) Multiplex lab-on-a-chip (LOC) for AMI biomarker antigens screening. Examples of fluorescence micrographs of a LOC multiplex assay for CRP, IL-1_, MYO and MPO are shown for non-AMI control, (d) NSTEMI and (e) STEMI patients. NEG, negative; CAL, calibrator (Modified from Floriano et al. Clin Chem, 2009 ).

Figure 3. Application of the cell-based NBC sensor system for cytological assessment of healthy and cancerous oral mucosa

(a) Exfoliative cytology specimens were obtained using the OralCDx® cytobrush (http://www.sopreventable.com/How2Use.htm); (b) Next, cells were captured on the membrane filter (panel i) followed by EGFR immunolabeling (panel ii, green) and staining of the cell cytoplasm (red) and nuclei (blue) for morphometric measurement; (c) Representative images of healthy epithelia (panel i) and a cancerous lesion (panel ii) examined using the NBC sensor illustrate the increase in EGFR expression and nuclear-to-cytoplasm ratio associated with disease progression; and (d) Logistic regression and ROC analysis of individual and combined biomarkers (adapted from Weigum et al. Cancer Detect. Prevent, 2010 ).