# Nanomaterials for Healthcare Biosensing Applications
## 4 Organic Nanomaterial Applications for Healthcare Biosensing
### Polymer Nanocomposites  
Polymer nanocomposites (PNCs) possess a variety of morphologies in addition to smart responsibilities and facile synthesis techniques. These unconventional qualities are responsible for the biocompatibility, environmental stability, superior electronic behaviour, and cost-effective nature of PNCs. PNCs are compatible with a variety of biomolecules, such as ODN, aptamers, proteins, and enzymes to enable biorecognition. Their large surface area and fast electron transfer rate in combination with the aforementioned characteristics make them ideal candidates for signal transduction in biosensing systems [230]. Robby and Park fabricated a colorimetric bacterial biosensor employing a nanocomposite of polymer dots (PDs) intercalated into montmorillonite (MMT) [318]. The PDs were made of carbonised boronic acid conjugated catechol-conjugated polyethylene glycol-grafted poly(dimethylamino)ethyl methacrylate and contained \(\beta\)CD. Fe\({}_{3}\)O\({}_{4}\) and CsWO\({}_{3}\) were also immobilised on the nanocomposite as recyclable metallic nanoparticles. Fluorescence quenching of the p-nitrophenyl phosphate (NPP) subtrate was achieved with alkalinephosphatase (ALPOx). The fluorescence-based biosensor provided a broad detection range for _E. coli_ and _S. aureus_ between 10\({}^{1}\) and 10\({}^{8}\) CFU mL\({}^{-1}\), with respective LODs of 5.25 cfu mL\({}^{-1}\) and 5.45 cfu mL\({}^{-1}\). Another nanocomposite combining polymer with clay was reported by Emre et al. for glucose biosensing [319]. The PNC consisted of poly(methylmethacrylate) (PMMA), 4-(2,3-dihydrothio [3,4-b][1,4]dioxin-5-yl)-7-(2,3-dihydrotio[3,4-b][1,4]dioxin- 7-yl)-2-benzyl-1-H-benzo[d] imidazole polymer (PBIPE), and the synthetic clay laponite (Lap). PBIPE is a conductive polymer with aromatic units that enable the hosting of GOx and PMMA-Lap with high efficacy. It acted as an excellent electron carrier and encouraged charge transfer. The nanocomposite enhanced the enzyme immobilisation and also contributed to signal amplification, leading to a detection range from 51 and a limit of 37.6 \(\upmu\)M. Another study also reported a glucose-based biosensor, using a nanocomposite of poly(brilliant cresyl blue) (pBCB) and MWCNT [320]. The use of ethaline deep eutectic solvent for the electro polymerisation of BCB significantly improved the sensing characteristics. The enzymatic sensor displayed an LOD of 2.9 \(\upmu\)M. The same sensor could also be employed for CAT detection when GOx was substituted with TSA. The LOD for CAT detection was found to be 3.9 \(\upmu\)M.  
Nguyen and co-workers reported a facile strategy to fabricate a glutamate sensor using a nanocomposite ink consisting of the ICP poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT-PSS) with MWCNTs, PtNPs and silicone rubber (SiRb) [321]. Finally, glutamate oxidase (GMTOx) was immobilised on nanocomposite. The ink was ultimately written on a PDMS substrate. The sensor was found to be highly selective, with linear responses between 10 and 600 \(\upmu\)M and an LOD of 0.2 \(\upmu\)M. The biosensing system was also employed to characterise the glutamate release from the spinal cord of a rat. It showed tremendous potential for application in implantable glutamate biosensors for patients with neurotraum. Divya et al. reported a polyindole(Pin)-zerovalent silver nanocomposite for the detection of DA at immiscible liquid/liquid interfaces with nanomolar sensing abilities [322]. Fluorescence measurements provided an extremely wide linear detection response from 40 nM to 12 \(\upmu\)M.  
PNCs are also frequently used for monitoring pharmaceutical drugs. Phukon et al. reported a polyhydroxyalkanoate (PHOA)-gold nanocomposite for artemisinin determination [323]. Artemisinin is a potent antimalarial drug. PHA was extracted from natural sources and the nanocomposite film was mounted on an ITO electrode prior to HRP immobilisation. No cross-linker was required in the fabrication of the biosensor.