Opportunities and challenges in translational application of ctDNA along with recent developments in chip-based ctDNA detection technologies have been reviewed.

Hepatitis C virus (HCV) is endemic in Pakistan and its burden is expected to increase in coming decades owing mainly to widespread use of unsafe medical procedures. The prevalence of HCV in Pakistan has previously been reviewed. However, the literature search conducted here revealed that at least 86 relevant studies have been produced since the publication of these systematic reviews. A revised updated analysis was therefore needed in order to integrate the fresh data. A systematic review of data published between 2010 and 2015 showed that HCV seroprevalence among the general adult Pakistani population is 6.8%, while active HCV infection was found in approximately 6% of the population. Studies included in this review have also shown extremely high HCV prevalence in rural and underdeveloped peri-urban areas (up to 25%), highlighting the need for an increased focus on this previously neglected socioeconomic stratum of the population. While a 2.45% seroprevalence among blood donors demands immediate measures to curtail the risk of transfusion transmitted HCV, a very high prevalence in patients attending hospitals with various non-liver disease related complaints (up to 30%) suggests a rise in the incidence of nosocomial HCV spread. HCV genotype 3a continues to be the most prevalent subtype infecting people in Pakistan (61.3%). However, recent years have witnessed an increase in the frequency of subtype 2a in certain geographical sub-regions within Pakistan. In Khyber Pakhtunkhwa and Sindh provinces, 2a was the second most prevalent genotype (17.3% and 11.3% respectively). While the changing frequency distribution of various genotypes demands an increased emphasis on research for novel therapeutic regimens, evidence of high nosocomial transmission calls for immediate measures aimed at ensuring safe medical practices.

Recent evidence suggests that small non-coding RNAs such as microRNA (miRNA) encapsulated in exosomes represent an important mechanism of communication between the cells. Exosomal miRNAs play an important role in carcinogenesis via enhancing the cell to cell communication and targeting the cell growth molecular pathways which in turn facilitate metastasis in cancers. Despite progressive advances, the current methods for the exosomal miRNA detection mostly rely on labor-intensive sequencing approaches which are often prone to amplification bias and require costly and bulky equipment. Herein, we report an electrochemical approach for the detection of cancer-derived exosomal miRNAs in human serum samples by selectively isolating the target miRNA using magnetic beads pre-functionalized with capture probes and then directly adsorbing the targets onto a gold electrode surface. The level of adsorbed miRNA is detected electrochemically in the presence of an [Fe(CN)₆]^4−/3− redox system. This method enabled an excellent detection sensitivity of 1.0 pM with a relative standard deviation (%RSD) of <5.5% in cancer cells and serum samples (n = 8) collected from patients with colorectal adenocarcinoma (CRC). We believe that our approach could be useful in clinical settings for the quantification of exosomal miRNA in cancer patients.

Dermal interstitial fluid (ISF) is a novel source of biomarkers that can be considered as an alternative to blood sampling for disease diagnosis and treatment. Nevertheless, in vivo extraction and analysis of ISF are challenging. On the other hand, microneedle (MN) technology can address most of the challenges associated with dermal ISF extraction and is well suited for long-term, continuous ISF monitoring as well as in situ detection. In this review, we first briefly summarise the different dermal ISF collection methods and compare them with MN methods. Next, we elaborate on the design considerations and biocompatibility of MNs. Subsequently, the fabrication technologies of various MNs used for dermal ISF extraction, including solid MNs, hollow MNs, porous MNs, and hydrogel MNs, are thoroughly explained. In addition, different sensing mechanisms of ISF detection are discussed in detail. Subsequently, we identify the challenges and propose the possible solutions associated with ISF extraction. A detailed investigation is provided for the transport and sampling mechanism of ISF in vivo. Also, the current in vitro skin model integrated with the MN arrays is discussed. Finally, future directions to develop a point-of-care (POC) device to sample ISF are proposed.