Synthetic nanopores have been used to study individual biomolecules in high thoroughput but their performance as sensors does not match biological ion channels. Controlling the translocation times of single-molecule analytes and their non-specific interaction with pore walls remain a challenge. Inspired by the olfactory sensilla of the insect antenna, here we show that coating nanopores with fluid bilayer lipids allows the pore diameters to be fine-tuned in sub-nanometre increments. Incorporation of mobile ligands in the lipid conferred specificity and slowed down the translocation of targeted proteins sufficiently to time-resolve translocation events of individual proteins. The lipid coatings also prevented pores from clogging, eliminated non-specific binding and enabled the translocation of amyloid-beta (Aβ) oligomers and fibrils. Through combined analysis of translocation time, volume, charge, shape and ligand affinity, different proteins were identified.

Progress towards the integration of technology into living organisms requires electrical power sources that are biocompatible, mechanically flexible, and able to harness the chemical energy available inside biological systems. Conventional batteries were not designed with these criteria in mind. The electric organ of the knifefish Electrophorus electricus (commonly known as the electric eel) is, however, an example of an electrical power source that operates within biological constraints while featuring power characteristics that include peak potential differences of 600 volts and currents of 1 ampere. Here we introduce an electric-eel-inspired power concept that uses gradients of ions between miniature polyacrylamide hydrogel compartments bounded by a repeating sequence of cation- and anion-selective hydrogel membranes. The system uses a scalable stacking or folding geometry that generates 110 volts at open circuit or 27 milliwatts per square metre per gel cell upon simultaneous, self-registered mechanical contact activation of thousands of gel compartments in series while circumventing power dissipation before contact. Unlike typical batteries, these systems are soft, flexible, transparent, and potentially biocompatible. These characteristics suggest that artificial electric organs could be used to power next-generation implant materials such as pacemakers, implantable sensors, or prosthetic devices in hybrids of living and non-living systems.

Biological protein pores and pore-forming peptides can generate a pathway for the flux of ions and other charged or polar molecules across cellular membranes. In nature, these nanopores have diverse and essential functions that range from maintaining cell homeostasis and participating in cell signaling to activating or killing cells. The combination of the nanoscale dimensions and sophisticated – often regulated – functionality of these biological pores make them particularly attractive for the growing field of nanobiotechnology. Applications range from single-molecule sensing to drug delivery and targeted killing of malignant cells. Potential future applications may include the use of nanopores for single strand DNA sequencing and for generating bio-inspired, and possibly, biocompatible visual detection systems and batteries. This article reviews the current state of applications of pore-forming peptides and proteins in nanomedicine, sensing, and nanoelectronics.

The redox behavior of cytochrome c (cyt c) adsorbed to gold electrodes modified with self-assembled monolayers (SAMs) depends on the SAM. This paper examines SAMs generated from alkanethiols terminating in trimethylammonium (1), sulfonate (2), methyl (3), amine (4), and carboxylic acid (5) groups and from an aromatic thiol (6). The redox potentials of cyt c adsorbed on SAMs of 1 and 5 are relatively close to the formal potential of native cyt c measured in solution. The redox potentials of cyt c adsorbed on SAMs of 3, 4, and 6 are significantly shifted from the formal potential, and a reduction peak at about 0.5 V more negative than the formal potential (that is, a value corresponding to a more difficult reduction) was observed in all three cases. These observations suggest that cyt c changes its conformation significantly on adsorption on these surfaces. No redox peaks were observed for cyt c adsorbed on SAMs of 2, although surface plasmon resonance (SPR) studies indicate that the SAMs of 2 irreversibly adsorbed approximately a double layer of cyt c. Mixed SAMs were also studied. Most interestingly, cyt c adsorbed on mixed SAMs formed from the combinations of 1 and 2 exhibited significantly slower electron transfer (0.3-1.2 s -1 ) than cyt c adsorbed on a homogeneous SAM of 1 (45 s -1 ). These observations suggest changes in protein orientation due to the presence of the sulfonate groups at the interface. This study suggests that electrochemical measurement can be a useful probe for the conformation and orientation of protein adsorbed on surfaces.

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