be introduced, which is mainly achieved by adding synthetic DNA barcode primers to beads. For these applications, the beads are mostly made of biocompatible polymers, for example, polyacrylamide beads in inDrop, [2] hydroxylated methacrylic polymer beads used in Drop-seq, [3] and polyacrylamide beads used in 10X Genomics. [8] Each of these chemically different beads has their own advantages and shortcomings. The inDrop polyacrylamide bead can be closely packed in a microfluidic device channel to achieve more than 95% loading of single bead per drop. [2] However, in the inDrop system, UV light is necessary to release primers from the bead, which somewhat complicates bead fabrication and makes it less cost effective. [9] Another shortcoming is that UV light may introduce damage to DNA or RNA and skew the results. [10,11] The Drop-seq system does not release primers from the bead and the reaction efficiency is low as reactions happen only near the surface of beads. [3] In the 10X Genomics platform, gel beads can be efficiently delivered into drops, but the comparably high cost and lack of flexibility in designing Droplet-based single cell sequencing technologies, such as inDrop, Dropseq, and 10X Genomics, are catalyzing a revolution in the understanding of biology. Barcoding beads are key components for these technologies. What is limiting today are barcoding beads that are easy to fabricate, can efficiently deliver primers into drops, and thus achieve high detection efficiency. Here, this work reports an approach to fabricate dissolvable polyacrylamide beads, by crosslinking acrylamide with disulfide bridges that can be cleaved with dithiothreitol. The beads can be rapidly dissolved in drops and release DNA barcode primers. The dissolvable beads are easy to synthesize, and the primer cost for the beads is significantly lower than that for the previous barcoding beads. Furthermore, the dissolvable beads can be loaded into drops with >95% loading efficiency of a single bead per drop and the dissolution of beads does not influence reverse transcription or the polymerase chain reaction (PCR) in drops. Based on this approach, the dissolvable beads are used for single cell RNA and protein analysis.
Formalin-fixed paraffin-embedded (FFPE) tissues constitute a vast and valuable patient material bank for clinical history and follow-up data. It is still challenging to achieve single cell/nucleus RNA (sc/snRNA) profile in FFPE tissues. Here, we develop a droplet-based snRNA sequencing technology (snRandom-seq) for FFPE tissues by capturing full-length total RNAs with random primers. snRandom-seq shows a minor doublet rate (0.3%), a much higher RNA coverage, and detects more non-coding RNAs and nascent RNAs, compared with state-of-art high-throughput scRNA-seq technologies. snRandom-seq detects a median of >3000 genes per nucleus and identifies 25 typical cell types. Moreover, we apply snRandom-seq on a clinical FFPE human liver cancer specimen and reveal an interesting subpopulation of nuclei with high proliferative activity. Our method provides a powerful snRNA-seq platform for clinical FFPE specimens and promises enormous applications in biomedical research.
Utilizing renewable energy to produce green hydrogen from saline water electrolysis is becoming increasingly important yet is largely challenged by the sluggish oxygen evolution reaction kinetics, the competitive anodic chlorine evolution reaction, and the resultant electrode corrosion. Here, we report an electrochemically activated Ni-Fe oxyhydroxide catalyst that delivers an early onset potential of 1.51 V at 100 mA cm −2 within mimic saline water of 0.5 M NaCl + 1 M NaOH. During the electrochemical activation, ex situ X-ray radiation and in situ Raman characterizations reveal the structural reconstruction of amorphous Ni (oxy)hydroxide generation and electronic structure modulation from Fe intercalation. Headspace gas chromatography and iodine titration results confirm the ∼100% Faradaic efficiency toward O 2 evolution on activated NiFeO x H y , whereas the long-term stability is assessed by an anion exchange membrane electrolyzer, demonstrating only 350 mV voltage decay during the 100 h continuous electrolysis at 500 mA cm −2 .
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