100 research outputs found
Magnetic micromotors crossing lipid membranes
No full textNano/micromotors are self-propelled particles that show enhanced motion upon being triggered by a stimulus. Their use in nanomedicine has been widely explored, with special focus on imaging or drug delivery. However, a thorough understanding of the requirements for more efficient locomotion is still lacking. In this paper, we assembled magnetically propelled motors of different sizes (i.e., 0.5, 1 and 4 μm) and surface chemistries (positive charge or PEGylated) and assessed their motion in the presence of giant unilamellar lipid vesicles (GUVs) of varying compositions (zwitterionic, negatively charged and saturated lipids). Unexpectedly, the size does not seem to be the dominating characteristics that governs the ability of the motors to cross lipid membranes. Specifically, the 0.5 μm PEGylated motors have very limited ability to cross the lipid membrane of GUVs due to their non-interacting nature compared to their equally sized positively charged counterparts. Furthermore, membranes made of saturated lipids and, in particular, in combination with a weak magnetic field facilitate motors’ crossing, regardless of their size. The results were validated by in-house data-driven statistical analysis that employs experimental data to allow for the identification of individual motor motion in the ensemble when meeting the lipid membranes. Altogether, we provide insight into motor locomotion when they interact with a biological barrier considering both the entire ensemble and the individual motors, which has the potential to support considerations of future motor designs.</p
Disintegrating polymer multilayers to jump-start colloidal micromotors
No full textColloidal systems with autonomous mobility are attractive alternatives to static particles for diverse applications. We present a complementary approach using pH-triggered disintegrating polymer multilayers for self-propulsion of swimmers. It is illustrated both experimentally and theoretically that homogenously coated swimmers exhibit higher velocity in comparison to their Janus-shaped counterparts. These swimmers show directional and random motion in microfluidic channels with a steep and shallow pH gradient, respectively. Further, a higher number of deposited polymer multilayers, steeper pH gradients and lower mass of the swimmers result in higher self-propulsion velocities. This new self-propulsion mechanism opens up unique opportunities to design, for instance, fast and yet biocompatible swimmers using the diverse tools of polymer chemistry to custom-synthesise the polymeric building blocks to assemble multilayers.</p
Recent Advances in Nano‐ and Micromotors
No full textNano- and micromotors are fascinating objects that can navigate in complex fluidic environments. Their active motion can be triggered by external power sources or they can exhibit self-propulsion using fuel extracted from their surroundings. The research field is rapidly evolving and has produced nano/micromotors of different geometrical designs, exploiting a variety of mechanisms of locomotion, being capable of achieving remarkable speeds in diverse environments ranging from simple aqueous solutions to complex media including cell cultures or animal tissue. This review aims to provide an overview of the recent developments with focus on predominantly experimental demonstrations of the various motor designs developed in the past 24 months. First, externally driven motors are discussed followed by considering fuel-driven approaches. Finally, a short future perspective is provided
Locomotion of micromotors due to liposome disintegration
No full textSynthetic micromotors are evaluated extensively in a range of biomedical, microscale transport, and environmental applications. Fundamental insight into micromotors that exhibit locomotion due to triggered disintegration of their associated liposomes is provided. Directed self-propulsion is observed when the lipid vesicles are solubilized using Triton X-100 (TX) and bile at sufficiently high concentrations. Directional motion, initiated by a propagating TX or bile gradient, is found when using a sufficiently high concentration of solubilization agents. On the other hand, a low bile concentration results in short-term reverse directional motion. The experimental and theoretical considerations offer valid fundamental understanding to complement the list of explored locomotion mechanisms for micromotors
Microswimmers with heat delivery capacity for 3D Cell spheroid penetration
No full textMicro- and nanoswimmers are a fast emerging concept that changes how colloidal and biological systems interact. They can support drug delivery vehicles, assist in crossing biological barriers, or improve diagnostics. We report microswimmers that employ collagen, a major extracellular matrix (ECM) constituent, as fuel and that have the ability to deliver heat via incorporated magnetic nanoparticles when exposed to an alternating magnetic field (AMF). Their assembly and heating properties are outlined followed by the assessment of their calcium-triggered mobility in aqueous solution and collagen gels. It is illustrated that the swimmers in collagen gel in the presence of a steep calcium gradient exhibit fast and directed mobility. The experimental data are supported with theoretical considerations. Finally, the successful penetration of the swimmers into 3D cell spheroids is shown, and upon exposure to an AMF, the cell viability is impaired due to the locally delivered heat. This report illustrates an opportunity to employ swimmers to enhance tissue penetration for cargo delivery via controlled interaction with the ECM
pH‐Responsive Motors and their Interaction with RAW 264.7 Macrophages
No full textAbstract Nano/micromotors are self‐propelled particles that use external stimuli to gain locomotion outperforming Brownian motion. Here, three different polymers are employed that are conjugated to silica particles through a pH‐labile linker. At slightly acidic pH, the linkers hydrolyze and release the polymeric chains, resulting in enhanced locomotion. The motors show a maximum velocity of ≈3 µm s−1 in cell media when poly(ethylene glycol) methyl ether methacrylate is asymmetrically distributed on the surface of the particles. Further, the motor internalization by RAW 264.7 macrophages was compared between motors, which have the polymer conjugated via a pH‐labile linker, and the irresponsive particles. Preliminary data indicate enhanced uptake, but further efforts are required to use responsive polymers to propel motors inside mammalian cells
TOWARDS SOFT ROBOTICS: 3D PRINTED HYDROGELS WITH PHOTO-THERMAL ACTUATION
No full textConventional robotics are based on rigid materials, such as stiff plastics, composites, metals, and ceramics. This makes them resilient and efficient at handling high loads and repetitive tasks. However, these robots still struggle with autonomy, as most need to be connected to a power supply. This either makes them static or coupled to a heavy battery, which is not favorable for locomotion. Thus a new field of robotics emerged, one that took inspiration from nature. To achieve this, the hard matter was substituted for soft matter, and by mimicking simple living organisms, i.e. plants and gastropods, the new soft robots could move, grasp and sense. Nevertheless, there are still challenges to overcome. Actuation is still very limited and slow, which makes moving inefficient. This work aims to study possible ways to create soft robots able to move vertically, either by swimming or jumping, by light actuation. To achieve the movement PNIPAM-based hydrogels were embedded with gold nanostars to function as photo-thermal converters. PNIPAM is known for its rapid thermal response, which results in the rapid expulsion of water for temperatures above its lowest critical solubility temperature. Together with 3D printing, this property can be exploited to create hydrogels capable of bending and relaxing. If done in quick succession, it could translate into vertical movement. 3D printed structures resulted in soft actuators capable of going from a flat initial state to a 400° curvature, with a thermal stimulus of 44 °C. With light stimulation, the gold nanostar-embedded hydrogels were able to raise their temperature 3.6 °C per min. In an aqueous environment, a 2 °C rise and a curvature of 26° were obtained after 2 min of light stimulation. It is possible to conclude that the heat generated by the gold nanostars is not sufficient to actuate the soft robots in an aqueous environment due to the heat dissipating into the water.A robótica convencional está fundamentada em materiais rígidos, como plásticos, compósitos, metais e cerâ-micas. O que resulta em robôs resilientes e eficazes para manuseio de cargas pesadas e a realização de tarefas repetitivas. Contudo, estes robôs têm a desvantagem de falta autonomia, pois a maioria precisa de estar conec-tada a uma fonte de alimentação, o que os torna estáticos, ou acoplados a uma bateria pesada, não favorecendo a sua locomoção. Assim, criou-se um campo na robótica inspirado pela natureza, substituindo a matéria dura por matéria mole. Imitando organismos simples, como plantas e gastrópodes, os novos soft robots foram ca-pazes de se deslocar, agarrar e sentir. Apesar disso, ainda há desafios a serem superados. A atuação ainda é muito limitada e lenta, o que torna a movimentação ineficiente. Este trabalho visa estudar possíveis formas de tornar soft robots capazes de se mover verticalmente, seja nadando ou saltando, por acionamento luminoso. Este projeto propõe a incorporação de nanoestrelas de ouro que funcionarão como conversores fototérmicos em hidrogéis à base de PNIPAM, o qual possui uma rápida resposta térmica e para temperaturas acima de sua temperatura crítica de solubilidade inferior resulta numa rápida expulsão de água do seu interior. Esta propri-edade, juntamente com impressão 3D, pode ser explorada para criar hidrogéis capazes de dobrar e relaxar, que em rápida sucessão, poderá traduzir-se em movimento vertical. Os resultados mostram que as estruturas 3D foram capazes de passar de um estado inicial plano para uma curvatura de 400°, com estímulo térmico de 44°C. Com estimulação luminosa, os hidrogéis incorporados com nanoestrelas de ouro foram capazes de au-mentar a sua temperatura 3,6 ° C por minuto. Em meio aquoso, resultou num aumento de 2°C e numa curvatura de 26°, que foi obtida após 2 min de estimulação luminosa, sem alteração mesmo após 10 min. É possível concluir que o calor gerado pelas nanoestrelas de ouro não é suficiente para acionar os soft robots num ambi-ente aquoso devido à dissipação do calor na água
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