Minimally invasive biopsy-based diagnostics in support of precision cancer medicine

Precision cancer medicine (PCM) to support the treatment of solid tumors requires minimally invasive diagnostics. Here, we describe the development of fine-needle aspiration biopsy-based (FNA) molecular cytology which will be increasingly important in diagnostics and adaptive treatment. We provide support for FNA-based molecular cytology having a significant potential to replace core needle biopsy (CNB) as a patient-friendly potent technique for tumor sampling for various tumor types. This is not only because CNB is a more traumatic procedure and may be associated with more complications compared to FNA-based sampling, but also due to the recently developed molecular methods used with FNA. Recent studies show that image-guided FNA in combination with ultrasensitive molecular methods also offers opportunities for characterization of the tumor microenvironment which can aid therapeutic decisions. Here we provide arguments for an increased implementation of molecular FNA-based sampling as a patient-friendly diagnostic method, which may, due to its repeatability, facilitate regular sampling that is needed during different treatment lines, to provide tumor information, supporting treatment decisions, shortening lead times in healthcare, and benefit healthcare economics.

Electropolymerized Receptor Coatings for the Quantitative Detection of Histamine with a Catheter-Based, Diagnostic Sensor

In this article, we report on the development of a catheter-based, biomimetic sensor as a step toward a minimally invasive diagnostic instrument in the context of functional bowel disorders. Histamine is a key mediator in allergic and inflammatory processes in the small intestines; however, it is a challenge to determine histamine levels at the duodenal mucosa, and classical bioreceptors are unsuitable for use in the digestive medium of bowel fluid. Therefore, we have developed molecularly imprinted polypyrrole coatings for impedimetric sensing electrodes, which enable the quantification of histamine in nondiluted, human bowel fluid in a broad concentration range from 25 nM to 1 μM. The electrodes show negligible cross-sensitivity to histidine as a competitor molecule and, for comparison, we also evaluated the response of nonimprinted and taurine-imprinted polypyrrole to histamine. Furthermore, using equivalent-circuit modeling, we found that the molecular recognition of histamine by polypyrrole primarily increases the resistive component of the electrode-liquid interface while capacitive effects are negligible. The sensor, integrated into a catheter, measures differentially to correct for nonspecific adsorption effects in the complex matrix of bowel fluids, and a single triggering frequency is sufficient to determine histamine concentrations. Together, these features are beneficial for real-time diagnostic tests.

Gelatin Methacryloyl Microneedle Patches for Minimally Invasive Extraction of Skin Interstitial Fluid

The extraction of interstitial fluid (ISF) from skin using microneedles (MNs) has attracted growing interest in recent years due to its potential for minimally invasive diagnostics and biosensors. ISF collection by absorption into a hydrogel MN patch is a promising way that requires the materials to have outstanding swelling ability. Here, a gelatin methacryloyl (GelMA) patch is developed with an 11 × 11 array of MNs for minimally invasive sampling of ISF. The properties of the patch can be tuned by altering the concentration of the GelMA prepolymer and the crosslinking time; patches are created with swelling ratios between 293% and 423% and compressive moduli between 3.34 MPa and 7.23 MPa. The optimized GelMA MN patch demonstrates efficient extraction of ISF. Furthermore, it efficiently and quantitatively detects glucose and vancomycin in ISF in an in vivo study. This minimally invasive approach of extracting ISF with a GelMA MN patch has the potential to complement blood sampling for the monitoring of target molecules from patients.

An improved digital polymerase chain reaction protocol to capture low-copy KRAS mutations in plasma cell-free DNA by resolving 'subsampling' issues

Genetic alterations responsible for the initiation of cancer may serve as immediate biomarkers for early diagnosis. Plasma levels of cell‐free DNA (cfDNA) in patients with cancer are higher than those in healthy individuals; however, the major technical challenge for the widespread implementation of cfDNA genotyping as a diagnostic tool is the insufficient sensitivity and specificity of detecting early‐stage tumors that shed low amounts of cfDNA. To establish a protocol for ultrasensitive droplet digital polymerase chain reaction (ddPCR) for quantification of low‐frequency alleles within a limited cfDNA pool, two‐step multiplex ddPCR targeting eight clinically relevant mutant KRAS variants was examined. Plasma samples from patients with colorectal (n = 10) and pancreatic cancer (n = 9) were evaluated, and cfDNA from healthy volunteers (n = 50) was utilized to calculate reference intervals. Limited cfDNA yields in patients with resectable colorectal and pancreatic cancers did not meet the requirement for efficient capture and quantification of rate mutant alleles by ddPCR. Eight preamplification cycles followed by a second‐run ddPCR were sufficient to obtain approximately 5000–10 000 amplified copies per ng of cfDNA, resolving the subsampling issue. Furthermore, the signal‐to‐noise ratio for rare mutant alleles against the extensive background presented by the wild‐type allele was significantly enhanced. The cutoff limit of reference intervals for mutant KRAS was determined to be ~ 0.09% based on samples from healthy individuals. The modification introduced in the ddPCR protocol facilitated the quantification of low‐copy alleles carrying driver mutations, such as oncogenic KRAS, in localized and early‐stage cancers using small blood volumes, thus offering a minimally invasive modality for timely diagnosis.

Multiphoton microscopy and microspectroscopy for diagnostics of inflammatory and neoplastic lung

Limitations of current medical procedures for detecting early lung cancers inspire the need for new diagnostic imaging modalities for the direct microscopic visualization of lung nodules. Multiphoton microscopy (MPM) provides for subcellular resolution imaging of intrinsic fluorescence from unprocessed tissue with minimal optical attenuation and photodamage. We demonstrate that MPM detects morphological and spectral features of lung tissue and differentiates between normal, inflammatory and neoplastic lung. Ex vivo MPM imaging of intrinsic two-photon excited fluorescence was performed on mouse and canine neoplastic, inflammatory and tumor-free lung sites. Results showed that MPM detected microanatomical differences between tumor-free and neoplastic lung tissue similar to standard histopathology but without the need for tissue processing. Furthermore, inflammatory sites displayed a distinct red-shifted fluorescence compared to neoplasms in both mouse and canine lung, and adenocarcinomas displayed a less pronounced fluorescence emission in the 500 to 550 nm region compared to adenomas in mouse models of lung cancer. These spectral distinctions were also confirmed by two-photon excited fluorescence microspectroscopy. We demonstrate the feasibility of applying MPM imaging of intrinsic fluorescence for the differentiation of lung neoplasms, inflammatory and tumor-free lung, which motivates the application of multiphoton endoscopy for the in situ imaging of lung nodules.