You are presented with multiple paper abstracts, alongside the associated literature review and chapter titles. Given the provided information, you are going to do a literature review. Please generate a coherent literature review that synthesizes the content, draws connections between different works, highlights major findings, and identifies any gaps in the existing research.

Literature Review Title: Plasmonic Optical Fiber-Grating Immunosensing: A Review 
Chapter Title:  Detection of Cancer Biomarkers 
1. Abstract of Cited Paper (BIB001):  This work presents the development of an innovative plasmonic optical fiber (OF) immunosensor for the detection of cytokeratin 17 (CK17), a biomarker of interest for lung cancer diagnosis. The development of this sensing platform is such that it can be assessed in non-liquid environments, demonstrating that a surface plasmon resonance (SPR) can be excited in this case. For this purpose, detections have been first carried out on CK17 encapsulated in gel matrix in the aim of mimicking tissue samples. Gold-coated OF immunosensors were embedded in a specifically designed packaging providing enough stiffness to penetrate into soft matters. Resulting reflected spectra have revealed, for the first time, the presence of a stable SPR signal recorded in soft matters. Experiments conducted to detect CK17 trapped in a porous polyacrylamide gel matrix have highlighted the specific and selective biosensor response towards the target protein. Finally, the packaged OF immunosensor has been validated by a preliminary test on human lung biopsy, which has confirmed the ex-vivo CK17 detection. Consequently, this work represents an important milestone towards the detection of biomarkers in tissues, which is still a clinical challenge for minimally-invasive in vivo medical diagnosis.

Literature Review:
This subsection summarizes the standard roadmap usually pursued to build plasmonic fiber-grating immunosensors. It shows the generic process, on the one hand, and focuses on a practical example linked to a relevant clinical issue, on the other hand: the minimally invasive detection of cancer biomarkers. In BIB001 BIB002 , the focus was made on cytokeratins (both CK7 and CK17) that are usually used for diagnosis in oncology, especially in the differential diagnosis of lung carcinomas, since primary tumors express CK7 while secondary tumors are deficient. Moreover, it has been demonstrated that cytokeratin fragments can be released from malignant cells and can reach the blood circulation. They are, therefore, easily accessible with an optical fiber that has been properly modified. Sensors prototyped for minimally invasive diagnosis, as those reported in BIB001 BIB002 , can be prepared following the main steps listed in Table 2 below. Table 2 . Main steps required to modify an optical-fiber section into a plasmonic fiber-grating immunosensor.