Advances in cell‐based biosensors using three‐dimensional cell‐encapsulating hydrogels

Abstract

Cell-based biosensors (CBBs) have emerged as promising biotechnical tools whereby various cell types can be used as basic sensing units to detect external stimuli. Specifically, CBBs have been applied in environmental monitoring, drug screening, clinical diagnosis and biosecurity. For these applications, CBBs offer several advantages over conventional molecular-based biosensors or living animal-based approaches, such as the capability to better mimic physiological situations, to enhance detection specificity and sensitivity, and to detect unknown compounds and toxins. On the other hand, existing CBBs suffer from several limitations, such as weak cell-substrate attachment, two-dimensional (2D) cell microenvironment, and limited shelf life. An emerging method for scaffold-free three-dimensional (3D) cell culture uses hydrogels to encapsulate cells. Advances in novel biomaterials and nano/microscale technologies have enabled encapsulation of cells in hydrogels to fabricate 3D CBBs, which hold great potential for addressing the limitation in existing 2D CBBs. Here, we present an overview of the emerging hydrogel-based CBBs, their applications in pathogen/toxin detection, drug screening and screening of cell-biomaterials interaction, and the associated challenges and potential solutions.

Three-Dimensional Cell Culture Systems and Their Applications in Drug Discovery and Cell-Based Biosensors

“…Therefore, 3D models can better replicate intrinsic physiological conditions and in vivo cellular responses to external stimuli compared to the 2D monolayer. 77,78,[80][81][82] As such, 3D-cultured cells can be the ideal sensing element in cell-based sensors to provide the most biologically relevant information and predictive data for in vivo tests. Cells grown in 3D culture can be incorporated into a biosensor either by direct attachment onto a biotic or abiotic substrate surface or by indirect attachment via entrapment in a biocompatible biopolymer.…”

“…78 Cellular responses to anticancer drugs were successfully monitored. Many 3D cell culture-based biosensors use the similar design as Figure 5A using natural or synthetic hydrogels to create 3D cell structures, since such systems can better represent the in vivo distribution of metabolites, nutrients, oxygen, and signaling molecules, 80 and more accurately mimic 3D tissue architecture, cell proliferation, motility, and migration via an artificial extracellular matrix. 86 The wide variety of commercially available hydrogels promotes facile selection of one or more suitable matrices for each cell line and/or biosensor application and helps overcome the disadvantageous features of some polymer matrices, such as variable compositions and properties (animal-based hydrogels) and requisite cytotoxic pretreatment steps (some synthetic hydrogels).…”

“…84 Collagen, collagen-chitosan, Matrigel, and fibrinogen matrices, alginate, Puramatrix scaffolds, and polyethylene glycol matrices have been used to fabricate 3D cell culture biosensors using various cell lines for drug screening, toxicology assays, and cell-biomaterial interaction screening, and for the identification of unknown pathogens and toxins. 80,86,87 An alternative to the hydrogel matrix for cell lines that reach confluence quickly or that naturally have little to no extracellular matrix is a gel-free system that uses an intercellular polymeric linker to create 3D cellular aggregates supported by neighboring cells. 84 Ong et al produced the gel-free 3D system using two carcinoma cell lines and a primary bone marrow mesenchymal stem line.…”

“…96 Another application of 3D biosensors is the rapid screening of cellbiomaterial interactions since biomaterial properties can modify cell behavior by influencing cell proliferation, survival, shape, migration, differentiation, as well as gene expression. 80 Wang et al designed a 3D tricellular composite that more accurately replicates human breast tissue than both co-cultures and monocultures by encapsulating human mammary epithelial cells, human fibroblasts, and adipocytes in a Matrigel-collagen gel. 32 This model is capable of bridging the gap between 2D cell culture models and whole-animal systems by helping clarify the role of cell-cell and cell-substrate interactions in neoplastic transformation and by better understanding how breast epithelium responds to ovarian hormones and induction of specific protein synthesis.…”

Bioinspired engineering of honeycomb structure – Using nature to inspire human innovation

“…Besides tissue engineering and regenerative medicine, honeycomb structures with high specific surface area as electrodes have also been applied in biosensors and bioelectronics fields [394]. Fulati et al [395] found that the nano-honeycomb flake ZnO material provided 1.8 times higher sensitivity than previously used ZnO nanorods under the same conditions.…”