Electro-addressable conductive alginate hydrogel for bacterial trapping and general toxicity determination

Abstract

In biosensors development, alginate hydrogels are a first choice for enabling stable biomolecules entrapment in biocompatible membranes obtained under soft physiological conditions. Although widely exploited, most alginate membranes are isolating and poorly repetitive, which limit their application in biosensing. Significant steps forward on improving repeatability and conductivity have been performed, but to date there is no single protocol for controlled deposition of live cells in replicable conductive alginate layers. Here, cell electrotrapping in conductive alginate hydrogels is examined in order to overcome these limitations. Conductive alginate-coated electrodes are obtained after potentiostatic electrodeposition of graphite-doped alginate samples (up to 4% graphite). The presence of graphite reduces electrode passivation and improves the electrochemical response of the sensor, although still significantly lower than that recorded with the naked electrode. Bacterial electrotrapping in the conductive matrix is highly efficient (4.4 × 10 cells per gel) and repetitive (CV < 0.5%), and does not compromise bacterial integrity or activity (cell viability = 56%). Biosensing based on ferricyanide respirometry yielded a four times increase in biosensor response with respect to non-conductive alginate membrane, providing toxicity values completely comparable to those reported. Cell electrotrapping in conductive hydrogels represents a step forward towards in high-sensitive cell-based biosensors development with important influence in environmental analysis, food and beverage industry as well as clinical diagnosis.

Behavior of Neural Cells Post Manufacturing and After Prolonged Encapsulation within Conductive Graphene-Laden Alginate Microfibers

“…[7, 32, 34] Alginate features favorable biocompatibility parameters such as cell-safe gelation conditions, high permeability, neutral pH, and low antigenicity. [16] Its structure of M- and G-blocks can be ionically crosslinked in the presence of divalant cations, such as Ca 2+ , Ba 2+ , Sr 2+ , and others; however, calcium crosslinkers are commonly used in biomedical applications because they are readily available and cost effective, and because calcium alginate hydrogels exhibit good swelling properties, which is important to maintain cell viability. [5, 6, 9, 35]…”

“…In this work, alginate was chosen for its cell compatibility, but its low conductivity needed to be addressed. There are a number of synthetic or carbon-based materials that can enhance the naturally low conductivity of alginate; these materials include synthetic polymers such as PEDOT:PSS, [13] silver nanowires, [14] graphite, [15, 16] graphene oxide, [17, 18] and pure graphene. [9, 18, 19] While pure graphene is favorable due to its extraordinary electrical, optical, biomedical, and mechanical properties, incorporating it into a stable aqueous pre-polymer solution for use with cell encapsulation is difficult, as the creation of graphene solutions typically requires the use of toxic or unstable chemicals, such as dimethylformamide (DMF) or N-methylpyyrolidone (NMP).…”

Conductive Hydrogels—A Novel Material: Recent Advances and Future Perspectives

“…To address the challenges of poor separation and repeatability of alginate, Vigués et al constructed conductive hydrogels comprising alginate through electrostatic deposition of graphite-doped alginate samples . Graphite decreases the polarizability of the electrode, improves the electrochemical response of the sensor, and can be used to immobilize stable living bacteria.…”

Microfluidic device for concentration and SERS‐based detection of bacteria in drinking water

“…As the concentration of pathogen microorganisms in drinking water is low (0-10 2 CFU/mL) [44], an efficient enrichment step is required to obtain a detectable signal. Capturing bacteria on porous structures has been reported as an effective way to concentrate microorganisms on a surface [7,45,46]. Even though these methods showed good sensitivities, all of them were time consuming (>60 min) as sample manipulation and preconcentration was carried out off-chip.…”

“…Even though these methods showed good sensitivities, all of them were time consuming (>60 min) as sample manipulation and preconcentration was carried out off-chip. Also, these approaches did not provide any spectral fingerprint information [46] or were limited to the indirect detection of an indicator molecule [45].…”