Beyond the more common chemical delivery strategies, several physical techniques are used to open the lipid bilayers of cellular membranes. These include using electric and magnetic fields, temperature, ultrasound or light to introduce compounds into cells, to release molecular species from cells or to selectively induce programmed cell death (apoptosis) or uncontrolled cell death (necrosis). More recently, molecular motors and switches that can change their conformation in a controlled manner in response to external stimuli have been used to produce mechanical actions on tissue for biomedical applications. Here we show that molecular machines can drill through cellular bilayers using their molecular-scale actuation, specifically nanomechanical action. Upon physical adsorption of the molecular motors onto lipid bilayers and subsequent activation of the motors using ultraviolet light, holes are drilled in the cell membranes. We designed molecular motors and complementary experimental protocols that use nanomechanical action to induce the diffusion of chemical species out of synthetic vesicles, to enhance the diffusion of traceable molecular machines into and within live cells, to induce necrosis and to introduce chemical species into live cells. We also show that, by using molecular machines that bear short peptide addends, nanomechanical action can selectively target specific cell-surface recognition sites. Beyond the in vitro applications demonstrated here, we expect that molecular machines could also be used in vivo, especially as their design progresses to allow two-photon, near-infrared and radio-frequency activation.

Amyloids are a broad class of proteins and peptides that can misfold and assemble into long unbranched fibrils with a cross-β conformation. These misfolding and aggregation events are associated with the onset of a variety of human diseases, among them, Alzheimer’s disease, Parkinson’s disease, and Huntington disease. Our understanding of amyloids has been greatly supported by fluorescent molecular probes, such as thioflavin-T, which shows an increase in fluorescence emission upon binding to fibrillar aggregates. Since the first application of thioflavin-T in amyloid studies nearly 30 years ago, many probes have emerged exhibiting a variety of responses to amyloids, such as intensity changes, shifts in fluorescence maxima, and variations in lifetimes, among many others. These probes have shed light on a variety of topics including the kinetics of amyloid aggregation, the effectiveness of amyloid aggregation inhibitors, the elucidation of binding sites in amyloid structures, and the staining of amyloids aggregates in vitro, ex vivo, and in vivo. In this Review, we discuss the design, properties, and application of photoactive probes used to study amyloid aggregation, as well as the challenges faced by current probes and techniques, and the novel approaches that are emerging to address these challenges.

not limited to solar energy harvesting, thin film transistors, light emitting diodes, sensors, optical limiters, and wearable devices. [1] Materials with enhanced optical limiting properties are of great demand in protecting various optical devices from laser radiations. A good optical limiter is a material which allows the optical radiation to pass through at low fluences but clamps the transmitted intensity as the incident laser fluence increases. This property of materials can be useful to fabricate devices for pulse shaping, [2] passive mode locking, [3] and eye protection against powerful lasers. [4] Typically, optical limiting happens in materials is due to reverse saturable absorption or excited state absorption. When a material is illuminated with a laser beam, it can absorb the laser light even when the incident laser energy is lower than the band gap of the material by two-photon absorption (2PA). However, in a direct band gap material in which the incident laser energy is higher than the band gap, the appreciable linear absorption induces free carrier absorption. [5] In the bulk form, most of the 2D dichalcogenides are indirect-band gap materials with conduction band minimum and valence band maximum located at Q and Γ points, respectively. [6] In the monolayer regime, the dichalcogenides The advancement in high power lasers has urged the requisite of efficient optical limiting materials for both eye and sensor protection. The discovery of atomically thin 2D transition metal dichacogenides with distinctive properties has paved the way for a variety of applications including optical limiting. Until recently, the optical limiting effect exhibited by 2D materials is inferior to the benchmark materials fullerene (C 60 ) and graphene. This article reports the optical limiting activity of the 2D transition metal dichal cogenide, titanium disulfide (TiS 2 ) nanosheets, using optical and photo acoustic zscan techniques. The 77% nonlinear optical limiting exhibited by the TiS 2 sheets with 73% lineartransmittance is superior to that of any other existing 2D dichalcogenide sheets, graphene, and the benchmark optical limiting material, C 60 . The enhanced nonlinear response is attributed to the concerted effect of 2photon and the induced excited state absorp tions. By using photoacoustic zscan, a unique tool developed to determine the nonlinear optical limiting mechanism in materials, it is found that the optical limiting exhibited by TiS 2 2D sheets and graphene are mainly due to nonlinear absorption rather than scattering effects. These results have opened the door for 2Ddichalcogenidematerialsbased highly efficient optical limiters, especially at low fluences.Since the advent of graphene, 2D materials have gained considerable attention owing to their incredible electrical and optical properties. Current efforts to utilize the unique features of these materials have been focused on their integration into a vast array of electrooptical applications. These include but are [+] Present address:

The formation of oligomeric soluble aggregates is related to the toxicity of amyloid peptides and proteins. In this manuscript, we report the use of a ruthenium polypyridyl complex ([Ru(bpy) 2 (dpqp)] 2+ ) to track the formation of amyloid oligomers at different times using photoluminescence anisotropy. This technique is sensitive to the rotational correlation time of the molecule under study, which is consequently related to the size of the molecule.[Ru(bpy) 2 (dpqp)] 2+ presents anisotropy values of zero when free in solution (due to its rapid rotation and long lifetime) but larger values as the size and concentration of amyloid-β (Aβ) oligomers increase. Our assays show that Aβ forms oligomers immediately after the assay is started, reaching a steady state at ∼48 h. SDS−PAGE, DLS, and TEM were used to confirm and characterize the formation of oligomers. Our experiments show that the rate of formation for Aβ oligomers is temperature dependent, with faster rates as the temperature of the assay is increased. The probe was also effective in monitoring the formation of α-synuclein oligomers at different times.