Abstract

The lives of ~900,000 US citizens have been extended by organ, and more recently, limb transplants from 1988 to 2021. Currently, there are over 250,000 patients in the US with a functioning kidney transplant. Unfortunately, the success of these methods requires lifelong drug treatment that includes immunosuppression drugs, such as tacrolimus. Furthermore, the dosage and regiment must be monitored to ensure that concentrations are sufficient to avoid transplant rejection, yet not lead to toxicity. Patients must constantly visit a hospital or clinic to have the drugs in their blood measured. Unfortunately, this burden has led to non-adherence and consequently, transplant failure in over 20% of patients, most often resulting in death. In an effort to reduce this burden, we have developed a simple to use assay to measure tacrolimus in saliva at home in 10-20 minutes. The assay employs a lateral flow assay cassette to separate tacrolimus from saliva, surface-enhanced Resonance Raman scattering (SERRS) dye probes as reporters to increase sensitivity, and a simple handheld Raman spectrometer to measure the tacrolimus concentration. Using this assay, tacrolimus spiked in saliva was successfully measured from 1 to 25 ng/mL.