Albert Swiston

Surface functionalization of living cells with multilayer patches.

We demonstrate that functional polyelectrolyte multilayer (PEM) patches can be attached to a fraction of the surface area of living, individual lymphocytes. Surface-modified cells remain viable at least 48 h following attachment of the functional patch, and patches carrying magnetic nanoparticles allow the cells to be spatially manipulated using a magnetic field. The patch does not completely occlude the cellular surface from the surrounding environment; this approach allows a functional payload to be attached to a cell that is still free to perform its native functions, as suggested by preliminary studies on patch-modified T-cell migration. This approach has potential for broad applications in bioimaging, cellular functionalization, immune system and tissue engineering, and cell-based therapeutics where cell-environment interactions are critical.

Cell-Based Drug Delivery Devices Using Phagocytosis- Resistant Backpacks

Macrophages, ubiquitous phagocytic cells in the human immune system, play a key role in homeostatic, immunological, and infl ammatory processes. [ 1‐2 ] Macrophages are widely distributed in various tissues and play a central role in clearing invading pathogens, dead cells, and foreign entities through phagocytosis. [ 3 ] Their wide presence in various organs and tissues makes them particularly suited to provide an immediate defense against invading threats. Moreover, macrophages are rapidly recruited to the diseased site by signaling molecules such as cytokines. Hence, macrophages are involved in a wide range of pathological conditions including cancer, atherosclerosis, various infl ammatory diseases such as vasculitis and asthma, and many others. Since macrophages play an indispensable role in most pathological conditions, they represent an ideal target for therapeutic applications. Several approaches seeking to use macrophages for targeted therapies involve feeding therapeutic nanoparticles to macrophages ex vivo, followed by re-injection of the macrophages to target the diseased site. This approach has shown promising results for treating HIV infections [ 4 ] , brain disorders, [ 5 ] and solid tumors. [ 6 ] While this strategy is effective for certain conditions, its applications are limited by the fact that the drug carriers are sequestered within the phagosome of macrophages, which reduces the release rates, and in certain cases, degrades the drug. This limitation can be potentially addressed by designing particles that: i) attach to the macrophage surface, ii) avoid internalization, iii) do not interfere with macrophage function, and iv) release the encapsulated drugs in a controlled manner. However, development of materials that simultaneously fulfi ll these requirements is a signifi cant challenge. Herein, we report the ability of cellular backpacks to successfully encapsulate and controllably release drugs and avoid phagocytic internalization while remaining on the macrophage’s surface. These characteristics point to new possibilities in creating cell-based bio-hybrid devices that leverage both the functions of the encapsulated cargo (drugs, nanoparticles, etc.) and the native functions of the cell. Cellular backpacks are fabricated using a standard photolithography lift-off technique of layer-by-layer and spray deposited fi lm. [ 7 ] Briefl y, a positive photoresist is patterned with regularly spaced 7- μ m-diameter holes that extend down to the substrate. Next, a layer-by-layer deposited fi lm consisting of alternating hydrogen bond donor‐acceptor pairs is deposited, and this layer comprises the release region that tethers the rest of the backpack to the substrate. Two hydrogen-bonded regions were used, and details can be found elsewhere. [ 7 ] Next, a Polyelectrolyte multilayer (PEM) of either (FITC-PAH/MNP) or (PDAC/SPS) is deposited to provide suffi cient mechanical rigidity for the backpack to survive the fi nal acetone sonication step [FITC =

Freely Suspended Cellular Backpacks Lead to Cell Aggregate Self-Assembly

Cellular “backpacks” are a new type of anisotropic, nanoscale thickness microparticle that may be attached to the surface of living cells creating a “bio-hybrid” material. Previous work has shown that these backpacks do not impair cell viability or native functions such as migration in a B and T cell line, respectively. In the current work, we show that backpacks, when added to a cell suspension, assemble cells into aggregates of reproducible size. We investigate the efficiency of backpack−cell binding using flow cytometry and laser diffraction, examine the influence of backpack diameter on aggregate size, and show that even when cell−backpack complexes are forced through small pores, backpacks are not removed from the surfaces of cells.

Layer-by-Layer Deposited Chitosan/Silk Fibroin Thin Films with Anisotropic Nanofiber Alignment

Chitosan/silk fibroin multilayer thin films were assembled using layer-by-layer deposition. The resultant multilayer films contained nanofibers aligned parallel to the dipping direction. Fiber deposition and orientation was enabled uniquely by a judicious choice of solvent and drying conditions and layer-by-layer assembly with chitosan. The deposition of oriented nanofibers was found to be the result of a unique combination of layer-by-layer and Langmuir-Blodgett type processing. Fiber orientation was confirmed by fast Fourier transform (FFT) analysis of optical micrographs and atomic force microscopy (AFM). Bidirectional fiber alignment was realized by rotating the substrate between multilayer deposition steps. Infrared spectroscopy revealed that the silk fibroin adopted the silk II secondary structure in the deposited films. We anticipate that these anisotropic films are able to combine the biocompatibility of a natural polymer system with the mechanical strength of SF, two properties useful in many biological applications including scaffolds suitable for guiding cell attachment and spreading.

Bioactive Polyelectrolyte Multilayers: Hyaluronic Acid Mediated B Lymphocyte Adhesion

A strategy was developed to produce thin, biopolymer-based polyelectrolyte multilayer films, based on hyaluronic acid and chitosan, that are able to effectively bind B lymphocytes. These films explore CD44-hyaluronate interactions and provide a method to make surface-bound B cell arrays without the need for nonselective covalent chemistry. The rational design of these films using solution deposition variables, such as ionic strength and pH, allows one to maximize and fine tune this binding efficiency ex vivo. This work suggests two important conditions for successfully attaching B cells to hyaluronate-containing polyelectrolyte multilayer films: (1) hyaluronic acid is required for the proposed CD44-mediated binding mechanism, and (2) hyaluronic acid deposition conditions that favor loops and tails, such as low pH and with added salt, result in more available CD44 binding ligands and higher cell binding efficiency. Chitosan-terminated films prepared without NaCl in the deposition solutions and hyaluronic acid-terminated films prepared with salt, both under pH 3.0 assembly conditions, presented a similar high lymphocyte binding efficiency. In the former case, however, the binding strength was weaker due to a significant electrostatic contribution to the binding. Bioactive polyelectrolyte multilayers for selective binding of lymphocytes hold great promise in fields ranging from cell-based biosensors to immune system engineering.

Ultrasound-mediated gastrointestinal drug delivery.

Ultrasound enables rapid and local delivery of drugs to the gastrointestinal tract for treatment of inflammatory diseases, such as ulcerative colitis. Drugs ride the wave across tissue barriers Macromolecular drugs traveling through the gastrointestinal tract are met by hard-to-breach tissue barriers that limit uptake and, in turn, dilute or prevent the drugs’ effects. Schoellhammer and colleagues repurposed a common technology in the clinic (ultrasound) to temporarily disrupt structural and physiological tissue barriers, allowing drugs to pass through. The initial application of a handheld ultrasonic probe was for rectal delivery of drugs, with a focus on treating a form of inflammatory bowel disease (IBD), called ulcerative colitis (UC). Patients with UC have few efficacious therapies, but drug enemas seem to work the best, as long as the patient isn’t suffering from diarrhea and the drug is absorbed quickly. The authors found that ultrasonic waves drove insulin and mesalamine into pig colonic tissue faster than natural absorption, without any physical or thermal damage to tissue. Ultrasound was also instrumental in encouraging mesalamine into mouse colonic tissues, leading to the resolution of acute colitis. Ultrasound-mediated drug delivery could be used for other drugs, such as hydrocortisone, and even macromolecules, such as insulin, as demonstrated by the authors, thus serving as a simple physical solution to the barrier challenge in gastrointestinal drug delivery. There is a significant clinical need for rapid and efficient delivery of drugs directly to the site of diseased tissues for the treatment of gastrointestinal (GI) pathologies, in particular, Crohn’s and ulcerative colitis. However, complex therapeutic molecules cannot easily be delivered through the GI tract because of physiologic and structural barriers. We report the use of ultrasound as a modality for enhanced drug delivery to the GI tract, with an emphasis on rectal delivery. Ultrasound increased the absorption of model therapeutics inulin, hydrocortisone, and mesalamine two- to tenfold in ex vivo tissue, depending on location in the GI tract. In pigs, ultrasound induced transient cavitation with negligible heating, leading to an order of magnitude enhancement in the delivery of mesalamine, as well as successful systemic delivery of a macromolecule, insulin, with the expected hypoglycemic response. In a rodent model of chemically induced acute colitis, the addition of ultrasound to a daily mesalamine enema (compared to enema alone) resulted in superior clinical and histological scores of disease activity. In both animal models, ultrasound treatment was well tolerated and resulted in minimal tissue disruption, and in mice, there was no significant effect on histology, fecal score, or tissue inflammatory cytokine levels. The use of ultrasound to enhance GI drug delivery is safe in animals and could augment the efficacy of GI therapies and broaden the scope of agents that could be delivered locally and systemically through the GI tract for chronic conditions such as inflammatory bowel disease.

Novel Electrodes for Underwater ECG Monitoring

We have developed hydrophobic electrodes that provide all morphological waveforms without distortion of an ECG signal for both dry and water-immersed conditions. Our electrode is comprised of a mixture of carbon black powder (CB) and polydimethylsiloxane (PDMS). For feasibility testing of the CB/PDMS electrodes, various tests were performed. One of the tests included evaluation of the electrode-to-skin contact impedance for different diameters, thicknesses, and different pressure levels. As expected, the larger the diameter of the electrodes, the lower the impedance and the difference between the large sized CB/PDMS and the similarly-sized Ag/AgCl hydrogel electrodes was at most 200 kΩ, in favor of the latter. Performance comparison of CB/PDMS electrodes to Ag/AgCl hydrogel electrodes was carried out in three different scenarios: a dry surface, water immersion, and postwater immersion conditions. In the dry condition, no statistical differences were found for both the temporal and spectral indices of the heart rate variability analysis between the CB/PDMS and Ag/AgCl hydrogel (p > 0.05) electrodes. During water immersion, there was significant ECG amplitude reduction with CB/PDMS electrodes when compared to wet Ag/AgCl electrodes kept dry by their waterproof adhesive tape, but the reduction was not severe enough to obscure the readability of the recordings, and all morphological waveforms of the ECG signal were discernible even when motion artifacts were introduced. When water did not penetrate tape-wrapped Ag/AgCl electrodes, high fidelity ECG signals were observed. However, when water penetrated the Ag/AgCl electrodes, the signal quality degraded to the point where ECG morphological waveforms were not discernible.

Physiologic Status Monitoring via the Gastrointestinal Tract

Reliable, real-time heart and respiratory rates are key vital signs used in evaluating the physiological status in many clinical and non-clinical settings. Measuring these vital signs generally requires superficial attachment of physically or logistically obtrusive sensors to subjects that may result in skin irritation or adversely influence subject performance. Given the broad acceptance of ingestible electronics, we developed an approach that enables vital sign monitoring internally from the gastrointestinal tract. Here we report initial proof-of-concept large animal (porcine) experiments and a robust processing algorithm that demonstrates the feasibility of this approach. Implementing vital sign monitoring as a stand-alone technology or in conjunction with other ingestible devices has the capacity to significantly aid telemedicine, optimize performance monitoring of athletes, military service members, and first-responders, as well as provide a facile method for rapid clinical evaluation and triage.

Planning Military Drinking Water Needs: Development of a User-Friendly Smart Device Application

Potable water is essential to maintain health and sustain military operations, but carrying and transporting water is a major logistical burden. Planning for group drinking water needs is complex, requiring understanding of sweat losses on the basis of intensity of activity, clothing biophysical parameters, and environmental conditions. Use of existing prediction equations is limited to tabled doctrine (e.g., Technical Bulletin, Medical 507) or to individuals with extensive expertise in thermal biophysics. In the present project, we translated the latest updated equations into a user-friendly Android application (Soldier Water Estimation Tool, SWET) that provides estimated drinking water required from 5 simple inputs based upon a detailed multiparametric sensitivity analysis. Users select from multiple choice inputs for activity level, clothing, and cloud cover, and manually enter exact values for temperature and relative humidity. Total drinking water needs for a unit are estimated in the Mission Planner tool on the basis of mission duration and number of personnel. In preliminary user acceptability testing, responses were overall positive in terms of ease of use and military relevance. Use of SWET for water planning will minimize excessive load (water) carriage in training and mission settings, and will reduce the potential for dehydration and/or hyponatremia to impair Warfighter health and performance.

Building low-power trustworthy systems: Cyber-security considerations for Real-Time Physiological Status Monitoring

Real-time monitoring of physiological data can reduce the likelihood of injury in noncombat military personnel and first-responders. MIT Lincoln Laboratory is developing a tactical Real-Time Physiological Status Monitoring (RT-PSM) system architecture and reference implementation named OBAN (Open Body Area Network), the purpose of which is to provide an open, government-owned framework for integrating multiple wearable sensors and applications. The OBAN implementation accepts data from various sensors enabling calculation of physiological strain information which may be used by squad leaders or medics to assess the teams health and enhance safety and effectiveness of mission execution. Security in terms of measurement integrity, confidentiality, and authenticity is an area of interest because OBAN system components exchange sensitive data in contested environments. In this paper, we analyze potential cyber-security threats and their associated risks to a generalized version of the OBAN architecture and identify directions for future research. The threat analysis is intended to inform the development of secure RT-PSM architectures and implementations.