Table 1.
Pros and cons of analytical techniques currently used in TDM, compared with SERS.
| Technique | Description | Pros | Cons |
|---|---|---|---|
| Chromatography-based methods | Chromatography separates individual compounds by their physical or chemical interaction with an immobile material. Once separated, combined selective MS techniques provide mass-based identification of the compounds |
Gold standard; Robust methods with superior sensitivity and sensibility; Relatively free from interferences; Multiplexing capabilities; Reduced drug class/metabolites cross reactivity |
Time consuming; Laboratory-developed tests; Interlaboratory variability; Matrix effects; High technical expertise required; High costs for installation, personnel training, and method validation; Need for sample clean-up |
| GC-MS/MS LC-MS/MS | |||
| Immunoassay platforms | Analyte is detected by its binding with a specific binding molecule, which in most cases is an analyte-specific antibody | Small amount of sample (<100 μL); Run on automated, continuous, random access systems; No need for sample clean-up; Multiplexing capabilities |
Several steps to achieve quantification of the analyte; Reduced specificity and sensitivity; Often show significant bias; Antibody cross-reactivity; Interferences from bilirubin, hemoglobin, high lipid content, very high or very low protein content, endogenous antibodies, various drugs and metabolites |
| ACMIA, CEDIA, CMIA, ELISA, EMIT, FPIA, MEIA, PETNIA | |||
| SERS-based methods | Inelastic light scattering on molecule adsorbed on the roughened metal surface is measured | No need for sample preparation; Fast measurement; Multiplexing capabilities; Availability of portable Raman spectrometer |
Very often high RSD of the SERS substrates; method optimization needed for each drug; |
GC-MS/MS, Gas Chromatography-tandem Mass Spectrometry; LC-MS/MS, Liquid Chromatography-tandem Mass Spectrometry; ACMIA, Antibody Conjugated Magnetic Immunoassay; CEDIA, Cloned Enzyme Donor Immunoassay; CMIA, Chemiluminescent Microparticle Immunoassay; ELISA, Enzyme-linked Immunosorbent Assay; EMIT, Enzyme Multiplied Immunoassay Technique; FPIA, Fluorescence Polarization Immunoassay; MEIA, Microparticle Enzyme Immunoassay; PETNIA, Particle-Enhanced Turbidimetric Inhibition Immunoassay; RSD, Relative Standard Deviation.