Owing to their small size, biocompatibility, unique and tunable photoluminescence, and physicochemical properties, graphene quantum dots (GQDs) are an emerging class of zero‐dimensional materials promising a wide spectrum of novel applications in bio‐imaging, optical, and electrochemical sensors, energy devices, and so forth. Their widespread use, however, is largely limited by the current lack of high yield synthesis methods of high‐quality GQDs. In this contribution, a facile method to electrochemically exfoliate GQDs from three‐dimensional graphene grown by chemical vapor deposition (CVD) is reported. Furthermore, the use of such GQDs for sensitive and specific detection of ferric ions is demonstrated.

Self-assembling biological complexes such as viral capsids have been manipulated to function in innovative nanotechnology applications. The E2 component of pyruvate dehydrogenase from Bacillus stearothermophilus forms a dodecahedral complex and potentially provides another platform for these purposes. In this investigation, we show that this protein assembly exhibits unusual stability and can be modified to encapsulate model drug molecules. To distill the E2 protein down to its structural scaffold core, we synthesized a truncated gene optimized for expression in Escherichia coli. The correct assembly and dodecahedral structure of the resulting scaffold was confirmed with dynamic light scattering and transmission electron microscopy. Using circular dichroism and differential scanning calorimetry, we found the thermostability of the complex to be unusually high, with an onset temperature of unfolding at 81.1 +/- 0.9 degrees C and an apparent midpoint unfolding temperature of 91.4 +/- 1.4 degrees C. To evaluate the potential of this scaffold for encapsulation of guest molecules, we made variants at residues 381 and 239 which altered the physicochemical properties of the hollow internal cavity. These mutants, yielding 60 and 120 mutations within this cavity, assembled into the correct architecture and exhibited high thermostability that was comparable to the wild-type scaffold. To show the applicability of this scaffold, two different fluorescent dye molecules were covalently coupled to the cysteine mutant at site 381. We demonstrate that these mutations can introduce non-native functionality and enable molecular encapsulation within the cavity while still retaining the dodecahedral structure. The unusually robust nature of this scaffold and its amenability to internal changes reveal its potential for nanoscale applications.

Protein nanocages have been explored as potential carriers in biomedicine. Formed by the self-assembly of protein subunits, the caged structure has three surfaces that can be engineered: the interior, the exterior and the intersubunit. Therapeutic and diagnostic molecules have been loaded in the interior of nanocages, while their external surfaces have been engineered to enhance their biocompatibility and targeting abilities. Modifications of the intersubunit interactions have been shown to modulate the self-assembly profile with implications for tuning the molecular release. We review natural and synthetic protein nanocages that have been modified using chemical and genetic engineering techniques to impart non-natural functions that are responsive to the complex cellular microenvironment of malignant cells while delivering molecular cargos with improved efficiencies and minimal toxicity.

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The mechanism of long-range charge transport across tunneling junctions with monolayers of ferritin is investigated. It is shown that the mechanism can be switched between coherent tunneling, sequential tunneling, and hopping by changing the iron content inside the ferritin. This study shows that ferritins are an interesting class of biomolecules to control charge transport.

Self-assembling protein cages provide a wide range of possible applications in nanotechnology. We report the first example of an engineered pH-dependent molecular switch in a virus-like particle. By genetically manipulating the subunit-subunit interface of the E2 subunit of pyruvate dehydrogenase, we introduce pH-responsive assembly into a scaffold that is natively stable at both pH 5.0 and 7.4. The redesigned protein module yields an intact, stable particle at pH 7.4 that dissociates at pH 5.0. This triggered behavior is especially relevant for applications in therapeutic delivery.

Misfolding of Amyloid β (Aβ) peptides leads to the formation of extracellular amyloid plaques. Molecular chaperones can facilitate the refolding or degradation of such misfolded proteins. Here, for the first time, we report the unique ability of Lipocalin-type Prostaglandin D synthase (L-PGDS) protein to act as a disaggregase on the pre-formed fibrils of Aβ(1–40), abbreviated as Aβ40, and Aβ(25–35) peptides, in addition to inhibiting the aggregation of Aβ monomers. Furthermore, our proteomics results indicate that L-PGDS can facilitate extraction of several other proteins from the insoluble aggregates extracted from the brain of an Alzheimer’s disease patient. In this study, we have established the mode of binding of L-PGDS with monomeric and fibrillar Aβ using Nuclear Magnetic Resonance (NMR) Spectroscopy, Small Angle X-ray Scattering (SAXS), and Transmission Electron Microscopy (TEM). Our results confirm a direct interaction between L-PGDS and monomeric Aβ40 and Aβ(25–35), thereby inhibiting their spontaneous aggregation. The monomeric unstructured Aβ40 binds to L-PGDS via its C-terminus, while the N-terminus remains free which is observed as a new domain in the L-PGDS-Aβ40 complex model.

A controllable and reproducible bipolar memristive protein nanodevice is fabricated by chemical immobilization of ferritin molecules within on‐wire lithography‐generated nanogaps. Control experiments suggest that programmable resistive switching is due to the electrochemical processes in the active centre of ferritin. Such ferritin‐based nanodevices with reversible resistance can be used for nonvolatile memory based on write‐read‐erase cycles.