**2.3. Biocompatibility of CPs**

Among the effective presentations of organic bioelectronics, ultra-thin electronic systems for surgical, point-of-care [46], diagnostic implants [47], ambient intelligence for daily-life assistance [48], soft robotics [49], conformable and self-sustaining bioelectronic elements for sports and recreation [48], or even disposable (biodegradable) electronics [50] for food packaging [51] or throw-away applications [52] can be listed. The connection of novel electronic elements with biosensing constituents will open the possibility for investigating disposable diagnostic and drug delivery platforms. This topic has been recently reviewed in detail [53, 54]. The organic bioelectronics field may prove to be the satisfactory host for greeting natural and nature-inspired carbon materials and a perfect base for achieving the ambitious purpose of "green" and sustainable electronics future.

charged bilayer polymeric layers for both anionic and cationic charge exclusion of interferes. Moving towards multiplexing, a PEDOT:PSS-based OECT biosensing platform integrated with microfluidics was investigated for contemporary screening of glucose, lactate and cholesterol in human saliva samples [5]. The final tool was tested with human volunteers before and after exercise to present comparative differences in their metabolite profiles under stimuli (**Figure 3B**) [67]. In a similar procedure, contemporary sensing of lactate and glucose was presented by integrating two OECT-based tools, each with a separate microfluidic channel. They created a prototype portable glucose sensor by linking a smartphone with the sensing platform through Bluetooth connection, highlighting the ease of integration of such devices for POC systems [68].

Conducting Polymers as Elements of Miniature Biocompatible Sensor

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Determination of cellular metabolites under different stimuli or environmental conditions can give useful prospects for drug discovery and toxicology. Larsen et al. used PEDOT:tosylate microelectrodes as an all polymer electrochemical chip for the determination of potassiuminduced transmitter release from neuron-like cells, presenting the potential of the procedure

**Figure 3.** Integrated point-of-care systems based on organic electronics. (A) Scheme of the conducting polymer electrochemical sensor for the direct measurement of creatinine from serum, according to [65]. (B) Schematic demonstrating the OECT-based multianalyte system, according to [67]; BSA, bovine serum albumin; ChOx, cholesterol

oxidase; GOx, glucose oxidase; HRP, horseradish peroxidase; lox, lactate oxidase.

**3.2. Metabolite sensing from whole cells**

Conducting polymers of pyrrole and thiophene connected by ester linkages have been considered for the generation of temporary scaffolds for cell attachment and proliferation for tissue engineering applications [22]. Moreover, these scaffolds are biodegradable [55]. The possibility of growing cells on CPs has proven the biocompatibility of these polymers [21, 56]. Additionally, recently the biocompatibility of PPy and PEDOT layers and PPy and PEDOT nanotubes was estimated by utilizing a dorsal root ganglion model [57]. The implantation of CPs *in vivo* for several weeks has led to only minimal inflammation, again pointing to low toxicities and good tissue compatibility [21, 55]. Moreover, Abidian and Martin [18] successfully presented that PEDOT nanotubes could record neuronal spikes about 30% more than control sites with a high signal-to-noise ratio (SNR) for 7 weeks post-implantation *in vivo*. In addition, there have been a number of reviews on CPs with regard to biomedical applications [22, 27, 55, 58–63].
