The ability to develop new and sensitive methods of biomolecule detection is crucial to the advancement of pre-clinical disease diagnosis and effective patient specific treatment. Surface enhanced Raman scattering (SERS) is an optical spectroscopy amenable to this goal, as it is capable of extremely sensitive biomolecule detection and multiplexed analysis. This perspective highlights where SERS has been successfully used to detect target biomolecules, specifically DNA and proteins, and where in vivo analysis has been successfully utilised. The future of SERS development is discussed and emphasis is placed on the steps required to transport this novel technique from the research laboratory to a clinical setting for medical diagnostics.

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Therapeutic drug monitoring (TDM) is required for pharmaceutical drugs with dosage limitations or toxicity issues where patients undergoing treatment with these drugs require frequent monitoring. This allows for the concentration of such pharmaceutical drugs in a patient's biofluid to be closely monitored in order to assess the pharmacokinetics, which could result in an adjustment of dosage or in medical intervention if the situation becomes urgent. Biosensors are a class of analytical techniques competent in the rapid quantification of therapeutic drugs and recent developments in instrumental platforms and in sensing schemes, as well as the emergence of nanobiosensors, have greatly contributed to the principal examples of these sensors for therapeutic drug monitoring. Based on initial success stories, it is clear that (nano)biosensors could pave the way for therapeutic drug monitoring of many commonly administered drugs and for new drugs that will be introduced to the market allowing for safe and optimal dosing across a wide range of pharmaceuticals. In this review, we report on the recent developments in biosensing and nanobiosensing techniques and, focussing mainly on anti-cancer agents and antibiotics, we discuss the different classes of molecules upon which therapeutic drug monitoring has already been successfully applied. The potential contributions of (nano)biosensors are also reviewed for the emerging areas of therapeutic response monitoring, where markers are monitored to ensure compliance of a patient to a treatment and in the area of cellular response to therapeutic drugs in order to identify cytotoxic effects of drugs on cells or to identify patients responding to a drug.

Three-dimensional (3D) printing has undergone an exponential growth in popularity due to its revolutionary and near limitless manufacturing capabilities. Recent trends have seen this technology utilized across a variety of scientific disciplines, including the measurement sciences, but precise fabrication of optical components for high-performance biosensing has not yet been demonstrated. We report here 3D printing of high-quality, custom prisms by stereolithography that enable Kretschmann-configured plasmonic sensing of bacterial toxins. Simple benchtop polishing procedures render a smooth surface that supports propagation of surface plasmon polaritons with a deposited gold layer, which exhibit high bulk refractive index sensitivities and are capable of discriminating trace levels of cholera toxin on a supported lipid membrane interface. Further evidence of the flexibility of this manufacturing technique is demonstrated with printed prisms of varied geometries and in situ monitoring of nanoparticle growth by total internal reflection spectroscopy. This work represents the first example of 3D printed light-guiding sensing platforms and demonstrates the versatility and broad perspective of 3D printing in optical detection.