In vitro culture systems for primary neurons have served as useful tools for neuroscience research. However, conventional in vitro culture methods are still plagued by challenging problems with respect to applications to neurodegenerative disease models or neuron-based biosensors and neural chips, which commonly require long-term culture of neural cells. These impediments highlight the necessity of developing a platform capable of sustaining neural activity over months. Here, we designed a series of polymeric bilayers composed of poly(glycidyl methacrylate) (pGMA) and poly(2-(dimethylamino)ethyl methacrylate) (pDMAEMA), designated pGMA:pDMAEMA, using initiated chemical vapor deposition (iCVD). Harnessing the surface-growing characteristics of iCVD polymer films, we were able to precisely engraft acetylcholine-like functionalities (tertiary amine and quaternary ammonium) onto cell culture plates. Notably, pGD3, a pGMA:pDMAEMA preparation with the highest surface composition of quaternary ammonium, fostered the most rapid outgrowth of neural cells. Clear contrasts in neural growth and survival between pGD3 and poly-l-lysine (PLL)-coated surfaces became apparent after 30 days in vitro (DIV). Moreover, brain-derived neurotrophic factor level continuously accumulated in pGD3-cultured neurons, reaching a 3-fold increase at 50 DIV. Electrophysiological measurements at 30 DIV revealed that the pGD3 surface not only promoted healthy maturation of hippocampal neurons but also enhanced the function of hippocampal ionotropic glutamate receptors in response to synaptic glutamate release. Neurons cultured long-term on pGD3 also maintained their characteristic depolarization-induced Ca2+ influx functions. Furthermore, primary hippocampal neurons cultured on pGD3 showed long-term survival in a stable state up to 90 days-far longer than neurons on conventional PLL-coated surfaces. Taken together, our findings indicate that a polymer thin film with optimal acetylcholine-like functionality enables a long-term culture and survival of primary neurons.
Keywords: BDNF; acetylcholine; brain-derived neurotrophic factor; iCVD; initiated chemical vapor deposition; neuron culture; polymer thin films.