The ideal in vitro recreation of the micro-tumor niche—although much needed for a better understanding of cancer etiology and development of better anticancer therapies—is highly challenging. Tumors are complex three-dimensional (3D) tissues that establish a dynamic cross-talk with the surrounding tissues through complex chemical signaling. An extensive body of experimental evidence has established that 3D culture systems more closely recapitulate the architecture and the physiology of human solid tumors when compared with traditional 2D systems. Moreover, conventional 3D culture systems fail to recreate the dynamics of the tumor niche. Tumor-on-chip systems, which are microfluidic devices that aim to recreate relevant features of the tumor physiology, have recently emerged as powerful tools in cancer research. In tumor-on-chip systems, the use of microfluidics adds another dimension of physiological mimicry by allowing a continuous feed of nutrients (and pharmaceutical compounds). Here, we discuss recently published literature related to the culture of solid tumor-like tissues in microfluidic systems (tumor-on-chip devices). Our aim is to provide the readers with an overview of the state of the art on this particular theme and to illustrate the toolbox available today for engineering tumor-like structures (and their environments) in microfluidic devices. The suitability of tumor-on-chip devices is increasing in many areas of cancer research, including the study of the physiology of solid tumors, the screening of novel anticancer pharmaceutical compounds before resourcing to animal models, and the development of personalized treatments. In the years to come, additive manufacturing (3D bioprinting and 3D printing), computational fluid dynamics, and medium- to high-throughput omics will become powerful enablers of a new wave of more sophisticated and effective tumor-on-chip devices.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its associated symptoms, named coronavirus disease 2019 (COVID-19), have rapidly spread worldwide, resulting in the declaration of a pandemic. When several countries began enacting quarantine and lockdown policies, the pandemic as it is now known truly began. While most patients have minimal symptoms, approximately 20% of verified subjects are suffering from serious medical consequences. Co-existing diseases, such as cardiovascular disease, cancer, diabetes, and others, have been shown to make patients more vulnerable to severe outcomes from COVID-19 by modulating host–viral interactions and immune responses, causing severe infection and mortality. In this review, we outline the putative signaling pathways at the interface of COVID-19 and several diseases, emphasizing the clinical and molecular implications of concurring diseases in COVID-19 clinical outcomes. As evidence is limited on co-existing diseases and COVID-19, most findings are preliminary, and further research is required for optimal management of patients with comorbidities.

The pH sensing devices can provide important health information with applications in infection detection, disease diagnosis, and personalized medicine. However, these devices are often expensive with modest flexibility and require bulky readout instruments, thus inappropriate for wearable, remote, and continuous health monitoring applications. Herein, an integrated, miniaturized, modular, wearable, battery‐free, biocompatible, flexible, 3D‐printed (WB2F3D) sensor system for on‐demand, continuous, wireless, and real‐time pH monitoring is proposed, developed, and fully characterized. The 3D‐printing of nanomaterials on skin‐like flexible substrates is innovatively applied to enable multimaterial and multilayer printing of the sensors, reusable electronic/communication circuity, and antennas in a tailorable, low‐cost, and time‐efficient manner. The battery‐free and flexible readout system is designed to enable wireless and on‐demand energy and data transmission for continuous and real‐time pH monitoring. This sensor system exhibits high sensitivity (≈|51.76| mV pH−1), specificity, repeatability, reproducibility toward various pH ranges (3.0–10.0), excellent mechanical flexibility, and outstanding biocompatibility (cell viability > = 90%). It successfully demonstrates the pH change monitoring in an ex situ hydrogel‐based wound model. The WB2F3D sensor system is envisioned to provide an integrated platform for accurate, on‐demand, battery‐free, wireless, and real‐time human health monitoring, and another step toward personalized medicine.