Person:

Ham, Donhee

Network-wide parallelization of neuronal intracellular recording and quantification of synaptic connections and their strengths is a challenge still open in neuroscience, with a mapping limit of ~300 connections. Here, we report a 4,096 microhole electrode array on a semiconductor chip for parallel intracellular recording and synaptic connectivity mapping of rat neuronal cultures using electroporation. The microholes are etched from a complementary metal-oxide semiconductor chip, and the final surface is coated with platinum black to increase roughness and the neuronal interface. The microhole array allows up to 90% average intracellular coupling rate with high coupling fidelity, generating network-wide intracellular recording data containing synaptic signals, and allows regaining intracellular coupling on the same neurons. We extract 70,000+ plausible synaptic connections amongst 2,000+ neurons, and catalogue them into inhibitory, weak/uneventful excitatory, strong/eventful excitatory chemical synaptic connections, and electrical synaptic connections, with an estimated overall error rate of around 5%. The reported scale of chemical and electrical synaptic mapping combines the advantages of patch clamp and extracellular multi-electrode array recordings, providing valuable insights into large-scale neural connectivity.

Massive parallelization of neuronal intracellular recording, which can measure synaptic signals across a network and thus can enable the mapping and characterization of synaptic connections, is a challenge still open in neuroscience, with the state-of-the-art limited to a mapping of ~300 synaptic connections. Here, we report a 4,096 platinum/platinum-black microhole electrode array fabricated on a complementary metal-oxide semiconductor electronic chip that substantially advances parallel intracellular recording and synaptic connectivity mapping. The microhole-neuron interface, together with current-clamp electronics in the underlying semiconductor chip, allows 90% average intracellular coupling rate with rat neuronal cultures, generating network-wide intracellular recording data that abound with synaptic signals. From these data we extract 70,000+ plausible synaptic connections amongst 2,000+ neurons, and catalogue them into inhibitory, weak/uneventful excitatory, and strong/eventful excitatory chemical synaptic connections, and electrical synaptic connections, with an estimated overall error rate of around 5%. The reported scale of synaptic connection mapping, with the ability to characterize synaptic connections, provides a step toward functional connectivity mapping of a large-scale neuronal network.

Parallelized DNA synthesis across a dense array of sites is crucial to high-throughput synthetic biology and diagnostics, and could potentially be used for DNA-based data storage. Phosphoramidite synthesis can achieve substantial parallelism, but relies on harmful solvents and centralized facilities. Enzymatic DNA synthesis in mild aqueous solution is safer and could be more accessible, but parallel demonstrations remain modest at an early stage. Here, we show that a complementary metal–oxide–semiconductor (CMOS) chip can be used to perform parallel enzymatic DNA synthesis of up to 64 distinct 38–39-nucleotide sequences (10–11-nucleotide feature sequences). The chip controls an array of 256 ring-electrode pairs (each one a programmable synthesis site) that can create an arbitrary pattern of localized acidity to enable DNA deprotection and subsequent enzymatic nucleotide incorporation. We also illustrate this parallel synthesis for data storage by encoding a 169-byte text. Our mechanistic analysis shows that shifting from an indirect to a direct local-acid chemistry route could lead to higher-throughput enzymatic synthesis that can scale with the CMOS chip.