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Electrochemical devices that transform electrical energy to mechanical energy through an electrochemical process have numerous applications ranging from soft robotics and micropumps to autofocus microlenses and bioelectronics. To date, achievement of large deformation strains and fast response times remains a challenge for electrochemical actuator devices operating in liquid wherein drag forces restrict the actuator motion and electrode materials/structures limit the ion transportation and accumulation. We report results for electrochemical actuators, electrochemical mass transfers, and electrochemical dynamics made from organic semiconductors (OSNTs). Our OSNTs electrochemical device exhibits high actuation performance with fast ion transport and accumulation and tunable dynamics in liquid and gel-polymer electrolytes. This device demonstrates an excellent performance, including low power consumption/strain, a large deformation, fast response, and excellent actuation stability. This outstanding performance stems from enormous effective surface area of nanotubular structure that facilitates ion transport and accumulation resulting in high electroactivity and durability. We utilize experimental studies of motion and mass transport along with the theoretical analysis for a variable–mass system to establish the dynamics of the electrochemical device and to introduce a modified form of Euler-Bernoulli’s deflection equation for the OSNTs. Ultimately, we demonstrate a state-of-the-art miniaturized device composed of multiple microactuators for potential biomedical application. This work provides new opportunities for next generation electrochemical devices that can be utilized in artificial muscles and biomedical devices.

Bidirectional vesicle transport along microtubules is necessary for cell viability and function, particularly in neurons. When multiple motors are attached to a vesicle, the distance a vesicle travels before dissociating is determined by the race between detachment of the bound motors and attachment of the unbound motors. Motor detachment rate constants ( k off ) can be measured via single-molecule experiments, but motor reattachment rate constants ( k on ) are generally unknown, as they involve diffusion through the bilayer, geometrical considerations of the motor tether length, and the intrinsic microtubule binding rate of the motor. To understand the attachment dynamics of motors bound to fluid lipid bilayers, we quantified the microtubule accumulation rate of fluorescently labeled kinesin-1 motors in a 2-dimensional (2D) system where motors were linked to a supported lipid bilayer. From the first-order accumulation rate at varying motor densities, we extrapolated a k off that matched single-molecule measurements and measured a 2D k on for membrane-bound kinesin-1 motors binding to the microtubule. This k on is consistent with kinesin-1 being able to reach roughly 20 tubulin subunits when attaching to a microtubule. By incorporating cholesterol to reduce membrane diffusivity, we demonstrate that this k on is not limited by the motor diffusion rate, but instead is determined by the intrinsic motor binding rate. For intracellular vesicle trafficking, this 2D k on predicts that long-range transport of 100-nm-diameter vesicles requires 35 kinesin-1 motors, suggesting that teamwork between different motor classes and motor clustering may play significant roles in long-range vesicle transport.

Functional nerve recovery after the injury is crucial in the field of neural interfaces. Although numerous technologies have already been established to promote nerve regeneration, effective nerve guidance in long distances (over 10 mm) still remains challenging. Herein, we report a novel technique to fabricate long gradients of substrate-bound laminin protein on conducting polymer films of poly(3,4-ethylenedioxythiophene) (PEDOT). The developed methodology allows for creation of various gradient profiles of laminin on PEDOT films to modulate axonal regeneration. These bioactive and conductive platforms can potentially be employed to promote axonal regeneration in the long nerve gaps.

Blood-brain barrier (BBB) imposes a major obstacle for entry of therapeutics to brain. In vitro BBB models that can provide reliable prediction of therapeutics’ ability to cross BBB are thus, critical for the advancement of brain therapeutics. Towards the development of an improved BBB model, here we studied the individual and combinatorial effect of few different culture conditions on the quality of the commonly used trans-well BBB model. Specifically, we investigated how the addition of (i) astrocyte co-culture, (ii) astrocyte-conditioned media (ACM), and (iii) astrocyte co-culture along with ACM, affects the characteristics of BBB. The resultant BBB models were characterized for trans-endothelial electrical resistance (TEER), permeability, and expression of a tight-junction protein ZO-1. We found that addition of ACM and astrocytes, individually, had similar impact on BBB’s TEER, increasing it by ~2 fold. Interestingly, the presence of both astrocytes and ACM had a significantly greater impact on TEER and increased it by ~3 fold. Addition of ACM, with and without astrocyte co-culture, led to a reduction in permeability of this BBB model. Moreover, addition of ACM and astrocyte co-culture, both individually and in combination, led to a noticeable increase in ZO-1 expression in the BBB endothelial cells. These findings provide a new approach for further improvement of the commonly used trans-well BBB system.

The limited effectiveness of current therapeutics against malignant brain gliomas has led to an urgent need for development of new formulations against these tumors. Chelator Dp44mT (di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone) presents a promising candidate to defeat gliomas due to its exceptional anti-tumor activity and its unique ability to overcome multidrug resistance. The goal of this study is to develop a targeted nano-carrier for Dp44mT delivery to glioma tumors and to assess its therapeutic efficacy in vitro and in vivo. Dp44mT is loaded into poly(ethylene glycol) (PEG)ylated poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) decorated with glioma-targeting ligand Interlukin 13 (IL13). IL13-conjugation enhanced the NP uptake by glioma cells and also improved their transport across an in vitro blood-brain-barrier (BBB) model. This targeted formulation showed an outstanding toxicity towards glioma cell lines and patient-derived stem cells in vitro, with IC50 values less than 125 nM, and caused no significant death in healthy brain microvascular endothelial cells. In vivo, when tested on a xenograft mouse model, IL13-conjugated Dp44mT-NPs reduced the glioma tumor growth by ≈62% while their untargeted counterparts reduced the tumor growth by only ≈16%. Notably, this formulation does not cause any significant weight loss or kidney/liver toxicity in mice, demonstrating its great therapeutic potential.

Electrospinning is a straightforward, cost-effective, and versatile technique for fabrication of polymeric micro/nanofibers with tunable structural properties. Controlling the size, shape, and spatial orientation of the electrospun fibers is crucial for utilization in drug delivery and tissue engineering applications. In this study, for the first time, we systematically investigate the effect of processing parameters, including voltage, syringe needle gauge, angular velocity of rotating wheel, syringe-collector distance, and flow rate on the size and alignment of electrospun PLGA fibers. Optimizing these parameters enabled us to produce highly aligned and monodisperse PLGA fibers (spatial orientation> 99% and coefficient of variation< 0.5). To assess the effect of fiber alignment on the release of encapsulated drugs from these fibers, we incorporated dexamethasone, an anti-inflammatory drug, within highly-aligned and randomly-oriented fibers with comparable diameters (~0.87 μm) and compared their release profiles. In-vitro release studies revealed that the aligned fibers had less burst release (~10.8% in 24 hr) and more sustained release (~8.8% average rate of change for 24 days) compared to the random fibers. Finally, the degradation modes of the aligned and random fibers after 25 days incubation were characterized and compared. The findings of this study can be applied for the development of 3D degradable aligned fibers for controlled drug release and tissue engineering applications.

The goal of this study is to apply and optimize the single emulsion technique for encapsulation of an anti-tumor drug, Di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone (Dp44mT), in nanoparticles (NPs) of poly(lactic-co-glycolic acid) (PLGA), as a step towards targeted delivery of this drug. We previously showed that the nanoprecipitation technique can effectively produce PLGA NPs carrying this drug. Here, we aim to examine the single emulsion technique as an alternative for the preparation of these NPs and to compare the resultant NPs to those from nanoprecipitation. We fabricated NPs with variations in (i) injection rate, (ii) the amount of surfactant poly (vinyl alcohol) (PVA) in aqueous phase, and (iii) concentration of PLGA in the organic phase. These NPs were characterized for size, surface potential, and encapsulation efficiency. The results revealed that increasing the injection rate (from manual addition to 90 mL/hr via syringe pump) greatly reduced the size of NPs (by 48%) and decreasing the PVA concentration in the aqueous phase (from 5 to 1% w/v) further reduced the NP size (by 32%) to 329 nm. All tested NP formulations had negative surface potential, suggesting good colloidal stability for these NPs. Focusing on the optimal injection rate and PVA percentage, we found that reducing the concentration of PLGA, from 100 to 1 mg/mL, significantly reduced the NP size to 136 nm, which is close to the optimal range for cancer therapeutic delivery. NPs produced by this method had a high encapsulation efficiency of 77% for Dp44mT and reducing the PLGA concentration slightly lowered this value to 74%. Overall, these NPs were comparable to those produced by nanoprecipitation and can thus, serve as an effective alternative for delivery of Dp44mT to cancer cells.

Membrane phase-separation is a mechanism that biological membranes often use to locally concentrate specific lipid species in order to organize diverse membrane processes. Phase separation has also been explored as a tool for the design of liposomes with heterogeneous and spatially organized surfaces. These “patchy” liposomes are promising platforms for delivery purposes, however their design and optimization through experimentation can be expensive and time-consuming. We developed a computationally efficient method based on the surface Cahn–Hilliard phase-field model to complement experimental investigations in the design of patchy liposomes. The method relies on thermodynamic considerations to set the initial state for numerical simulations. We show that our computational approach delivers not only qualitative pictures, but also accurate quantitative information about the dynamics of the membrane organization. In particular, the computational and experimental results are in excellent agreement in terms of lipid domain area fraction, total lipid domain perimeter over time and total number of lipid domains over time for two different membrane compositions (DOPC:DPPC with a 2:1 M ratio with 20% Chol and DOPC:DPPC with a 3:1 M ratio with 20% Chol). Thus, the computational phase-field model informed by experiments has a considerable potential to assist in the design of liposomes with spatially organized surfaces, thereby containing the cost and time required by the design process.

Conducting polymer (CP) actuators are promising devices for biomedical applications such as artificial muscles and drug delivery systems. Here, we report a tri-layer actuator based on poly(pyrrole) (PPy) microtubes (PPy MTs) doped with poly(sodium-p-styrenesulfonate) (PSS) and constructed on a passive layer of gold-coated poly-propylene (PP) film. The PPy MTs were fabricated using electrochemical deposition of PPy around poly(lactic-co-glycolic acid) (PLGA) fiber templates, followed by template removal. The PPy MTs were subjected to a redox process using cyclic voltammetry in 0.1 M NaPSS electrolyte solution as the potential was swept between -0.8 V and +0.4 V for 5 cycles at the scan rates of 10, 50, 100, and 200 mV/s. The bending behavior of the PPy MTs actuator was investigated by measuring the deflection of actuator tip resulting from the expansion/contraction strain of PPy MTs. The PPy MTs actuator showed a reversible bending movement during each potential cycle. The maximum deflection of actuator decreased by increasing the scan rate that was confirmed by calculating the actuation strain generated during each cycle at various scan rates.

Bidirectional vesicle transport along microtubules is necessary for cell viability and function, particularly in neurons. When multiple motors are attached to a vesicle, the distance a vesicle travels before dissociating is determined by the race between detachment of the bound motors and attachment of the unbound motors. Motor detachment rate constants (koff) can be measured via single-molecule experiments, but motor reattachment rate constants (kon) are generally unknown, as they involve diffusion through the bilayer, geometrical considerations of the motor tether length, and the intrinsic microtubule binding rate of the motor. To understand motor attachment dynamics during vesicle transport, we quantified the microtubule accumulation rate of fluorescently-labeled kinesin-1 motors in a 2D system where motors were linked to a supported lipid bilayer. From the first-order accumulation rate at varying motor densities, we extrapolated a koff that matched single-molecule measurements, and measured a two-dimensional kon for membrane-bound kinesin-1 motors binding to the microtubule. This kon is consistent with kinesin-1 being able to reach roughly 20 tubulin subunits when attaching to a microtubule. By incorporating cholesterol to reduce membrane diffusivity, we demonstrate that this kon is not limited by the motor diffusion rate, but instead is determined by the intrinsic motor binding rate. For intracellular vesicle trafficking, this two-dimensional kon predicts that long-range transport of 100 nm diameter vesicles requires 35 kinesin-1 motors, suggesting that teamwork between different motor classes and motor clustering may play significant roles in long-range vesicle transport.Significance StatementLong-distance transport of membrane-coated vesicles involves coordination of multiple motors such that at least one motor is bound to the microtubule at all times. Microtubule attachment of a membrane-bound motor comprises two steps – diffusing through the lipid bilayer to a binding zone near the microtubule, followed by binding. Using a 2D supported lipid bilayer system, we show that membrane diffusion is not the limiting factor for motor attachment. This result suggests that in cells kinesin-1 binding kinetics are not altered by the membrane composition of vesicle cargos. The intrinsically slow binding properties of kinesin-1 suggest that divergent motor binding kinetics and motor clustering regulate long-range vesicle transport.

Conservative and non-conservative phase-field models are considered for the numerical simulation of lateral phase separation and coarsening in biological membranes. An unfitted finite element method is devised for these models to allow for a flexible treatment of complex shapes in the absence of an explicit surface parametrization. For a set of biologically relevant shapes and parameter values, the paper compares the dynamic coarsening produced by conservative and non-conservative numerical models, its dependence on certain geometric characteristics and convergence to the final equilibrium

This paper describes the modulation of polymeric nanoparticle (NP) preparation to produce an optimal nanocarrier for delivery of the potent anti-tumor iron chelator, Di2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone (Dp44mT) towards application in cancer therapy. We have previously shown the potential of poly (lactic-co-glycolic acid) (PLGA) NPs as a nano-carrier for delivery of Dp44mT to malignant cells. The focus of this study is to alter the fabrication parameters to improve the characteristics of these NPs as a delivery vehicle for Dp44mT. To this end, PLGA NPs encapsulating Dp44mT are fabricated using the nanoprecipitation method with systematic variations in (i) the amount of surfactant poly (vinyl alcohol) (PVA) in aqueous phase, and (ii) the drug to polymer ratio in organic phase. The resultant NPs are characterized for size, surface potential, encapsulation efficiency, and drug release profile. Results of this study showed that increasing the PVA % (within the examined range of 0.5-4% w/v) and decreasing the Dp44mT to PLGA ratio (within the tested range of 0.0375-0.3: 1 mg/mL) both led to an increase in drug encapsulation efficiency. Focusing on the optimal PVA percentage, we found that the changes in drug to polymer ratio did not have a significant impact on the size distribution and surface potential of Dp44mT-NPs and these NPs remained in the desirable range of 80-120 nm. Lastly, the release of Dp44mT from NPs differed for different Dp44mT: PLGA ratios, providing a means to further optimize the NP formulation for future cancer treatment applications.

This paper describes the preparation and characterization of polymeric nanoparticles loaded with a potent anti-tumor metal chelator, Di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone (Dp44mT) for delivery to cancer cells. Metal chelators have been increasingly studied for their anti-cancer properties that rely on the high demand of neoplastic cells for iron. Dp44mT has previously shown great antiproliferative characteristics in several cancers including breast cancer and melanoma. To further expand the application of this highly cytotoxic agent for cancer treatment and to enable its specific delivery to malignant cells, here we apply nano-scale particles (NPs) of biodegradable poly(lactic-co-glycolide) (PLGA) for encapsulation of Dp44mT and evaluate its effectiveness in vitro. The results demonstrated that Dp44mT was efficiently encapsulated in PLGA particles. Resulting NPs were uniform in size and shape and had good colloidal stability. Moreover, Dp44mT encapsulation in PLGA enhanced the water solubility of this agent. Lastly, the present formulation showed high level of cytotoxicity in glioma cells. Together, these results show the potential of PLGA NPs as a nano-carrier for Dp44mT with no apparent impact on the anti-tumor activity of this compound.

A new methodology for selective electropolymerization of conducting polymer films using wet hydrogel stamps is presented. The ability of this simple method to generate patterned films of conducting polymers with multiple surface chemistries in a one-step process and to incorporate fragile biomolecules in these films is demonstrated.

This study aims to develop a new anti-cancer formulation based on the chelator Dp44mT (Di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone). Dp44mT has outstanding anti-tumor activity and the unique ability to overcome multidrug-resistance in cancer cells. This highly toxic compound has thus far only been applied in free form, limiting its therapeutic effectiveness. To reach its full therapeutic potential, however, Dp44mT should be encapsulated in a nano-carrier that would enable its selective and controlled delivery to malignant cells. As the first step towards this goal, here we encapsulate Dp44mT in nanoparticles (NPs) of poly(lactic-co-glycolic acid) (PLGA), characterize this nano-formulation, and evaluate its therapeutic potential against cancer cells in vitro. Our results showed that the Dp44mT-loaded NPs were homogenous in shape and size, and had good colloidal stability. These PLGA NPs also showed high encapsulation efficiency and loading capacity for Dp44mT and enabled the sustained and tunable release of this chelator. Dp44mT-NPs were uptaken by cancer cells, showed a strong and dose-dependent cytotoxicity towards these cells, and significantly increased apoptotic cell death, in both monolayer and spheroid tumor models. This formulation had a low-level of toxicity towards healthy control cells, indicating an inherent selectivity towards malignant cells. These results demonstrate the great potential of this novel Dp44mT-based nano-formulation for the use in cancer therapy.

Synthetic nanopores have been used to study individual biomolecules in high throughput, but their performance as sensors does not match that of biological ion channels. Challenges include control of nanopore diameters and surface chemistry, modification of the translocation times of single-molecule analytes through nanopores, and prevention of non-specific interactions with pore walls. Here, inspired by the olfactory sensilla of insect antennae, we show that coating nanopores with a fluid lipid bilayer tailors their surface chemistry and allows fine-tuning and dynamic variation of pore diameters in subnanometre increments. Incorporation of mobile ligands in the lipid bilayer conferred specificity and slowed the translocation of targeted proteins sufficiently to time-resolve translocation events of individual proteins. 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 their translocation time, volume, charge, shape and ligand affinity, different proteins were identified.

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.

Organic electronic materials are rapidly emerging as superior replacements for a number of conventional electronic materials, such as metals and semiconductors. Conducting polymers, carbon nanotubes, graphenes, organic light-emitting diodes, and diamond films fabricated via chemical vapor deposition are the most popular organic bioelectronic materials that are currently under active research and development. Besides the capability to translate biological signals to electrical signals or vice versa, organic bioelectronic materials entail greater biocompatibility and biodegradability compared to conventional electronic materials, which makes them more suitable for biomedical applications. When patterned, these materials bring about numerous capabilities to perform various tasks in a more-sophisticated and high-throughput manner. Here, we provide an overview of the unique properties of organic bioelectronic materials, different strategies applied to pattern these materials, and finally their applications in the field of biomedical engineering, particularly biosensing, cell and tissue engineering, actuators, and drug delivery.

Bioinspired artificial water channels aim to combine the high permeability and selectivity of biological aquaporin (AQP) water channels with chemical stability. Here, we carefully characterized a class of artificial water channels, peptide-appended pillar[5]arenes (PAPs). The average single-channel osmotic water permeability for PAPs is 1.0(± 0.3) × 10(-14) cm(3)/s or 3.5(± 1.0) × 10(8) water molecules per s, which is in the range of AQPs (3.4 ∼ 40.3 × 10(8) water molecules per s) and their current synthetic analogs, carbon nanotubes (CNTs, 9.0 × 10(8) water molecules per s). This permeability is an order of magnitude higher than first-generation artificial water channels (20 to ∼ 10(7) water molecules per s). Furthermore, within lipid bilayers, PAP channels can self-assemble into 2D arrays. Relevant to permeable membrane design, the pore density of PAP channel arrays (∼ 2.6 × 10(5) pores per μm(2)) is two orders of magnitude higher than that of CNT membranes (0.1 ∼ 2.5 × 10(3) pores per μm(2)). PAP channels thus combine the advantages of biological channels and CNTs and improve upon them through their relatively simple synthesis, chemical stability, and propensity to form arrays.

Gramicidin A is a small and well characterized peptide that forms an ion channel in lipid membranes. An important feature of gramicidin A (gA) pore is that its conductance is affected by the electric charges near the its entrance. This property has led to the application of gramicidin A as a biochemical sensor for monitoring and quantifying a number of chemical and enzymatic reactions. Here, a mathematical model of conductance changes of gramicidin A pores in response to the presence of electrical charges near its entrance, either on membrane surface or attached to gramicidin A itself, is presented. In this numerical simulation, a two dimensional computational domain is set to mimic the structure of a gramicidin A channel in the bilayer surrounded by electrolyte. The transport of ions through the channel is modeled by the Poisson-Nernst-Planck (PNP) equations that are solved by Finite Element Method (FEM). Preliminary numerical simulations of this mathematical model are in qualitative agreement with the experimental results in the literature. In addition to the model and simulations, we also present the analysis of the stability of the solution to the boundary conditions and the convergence of FEM method for the two dimensional PNP equations in our model.

Giant proteoliposomes mimic natural cell membranes and provide excellent models for membrane biophysical studies such as membrane phase separation, lipid-protein interactions, and functional studies of membrane proteins. Here, we present a simple and versatile approach for producing a large number of uniformly-sized giant proteoliposomes in a parallel fashion. This approach that combines the versatile technique of hydrogel-based microcontact printing and the commonly used technique of electroformation is efficient, low-cost, and doesn't require any specialized equipment. The resulting liposomes are attached to the surface in an array format, enabling rapid data collection for statistical analysis of membrane processes. We applied these vesicles for monitoring lipid-protein and protein-protein binding interactions. Alternatively, liposomes can be easily detached from the surface to produce a large number of giant liposomes with functional membrane proteins. We employed these vesicles for studying the channel activity of aquaporin protein and for monitoring material transport across lipid membranes. This approach may further be applicable to produce giant polymerosomes with increased stability compared to liposomes. The presented method can, hence, be useful in biomaterials, biotechnology, and biosensing applications as well as in the biophysical fundamental studies.View Large Image | View Hi-Res Image | Download PowerPoint Slide

A simple and versatile method for the Formation of Arrays of Giant Vesicles with Controlled Size and Composition. The ability of this technique to generate arrays of giant liposomes from a wide range of membrane lipids and protein compositions is demonstrated. The resulting vesicles are utilized for studying protein activity, lipid-protein interactions, and protein-protein interactions.