Kathleen O'Donnell

Hyperthermia-Induced Drug Delivery from Thermosensitive Liposomes Encapsulated in an Injectable Hydrogel for Local Chemotherapy

A novel drug delivery system, enabling an in situ, thermally triggered drug release is described, consisting of an injectable thermoresponsive chitosan hydrogel containing doxorubicin-loaded thermosensitive liposomes. The design, fabrication, characterization, and an assessment of in vitro bioactivity of this formulation is detailed. Combining on-demand drug delivery with in situ gelation results in a promising candidate for local chemotherapy.

A soft exosuit for patients with stroke: Feasibility study with a mobile off-board actuation unit

In this paper, we present the first application of a soft exosuit to assist walking after stroke. The exosuit combines textile garments with cable driven actuators and is lighter and more compliant as compared to traditional rigid exoskeletons. By avoiding the use of rigid elements, exosuits offer greater comfort, facilitate donning/doffing, and do not impose kinematic restrictions on the wearer - all while retaining the ability to generate significant moments at target joints during walking. The stroke-specific exosuit adapted from previous exosuit designs provides unilateral assistance to the paretic limb during walking. This paper describes stroke-specific design considerations, the design of the textile components, the development of a research-focused, mobile off-board actuation unit capable of testing the exosuit in a variety of walking conditions, a real-time gait detection and control algorithm, and proof-of-principle data validating the use of the exosuit in the chronic stroke population. Ultimately, we demonstrate reliable tracking of poststroke gait, appropriate timing of assistive forces, and improvements in key gait metrics. These preliminary results demonstrate the feasibility and promise of exosuits for poststroke gait assistance and training. Future work will involve the creation of a portable, body-worn system based on the specifications obtained from such feasibility studies that will enable community-based rehabilitation.

Reducing Circumduction and Hip Hiking During Hemiparetic Walking Through Targeted Assistance of the Paretic Limb Using a Soft Robotic Exosuit

Objective The aim of the study was to evaluate the effects on common poststroke gait compensations of a soft wearable robot (exosuit) designed to assist the paretic limb during hemiparetic walking. Design A single-session study of eight individuals in the chronic phase of stroke recovery was conducted. Two testing conditions were compared: walking with the exosuit powered versus walking with the exosuit unpowered. Each condition was 8 minutes in duration. Results Compared with walking with the exosuit unpowered, walking with the exosuit powered resulted in reductions in hip hiking (27 [6%], P = 0.004) and circumduction (20 [5%], P = 0.004). A relationship between changes in knee flexion and changes in hip hiking was observed (Pearson r = −0.913, P < 0.001). Similarly, multivariate regression revealed that changes in knee flexion (&bgr; = −0.912, P = 0.007), but not ankle dorsiflexion (&bgr; = −0.194, P = 0.341), independently predicted changes in hip hiking (R2 = 0.87, F(2, 4) = 13.48, P = 0.017). Conclusions Exosuit assistance of the paretic limb during walking produces immediate changes in the kinematic strategy used to advance the paretic limb. Future work is necessary to determine how exosuit-induced reductions in paretic hip hiking and circumduction during gait training could be leveraged to facilitate more normal walking behavior during unassisted walking.

Biomechanical mechanisms underlying exosuit-induced improvements in walking economy after stroke

ABSTRACT Stroke-induced hemiparetic gait is characteristically asymmetric and metabolically expensive. Weakness and impaired control of the paretic ankle contribute to reduced forward propulsion and ground clearance – walking subtasks critical for safe and efficient locomotion. Targeted gait interventions that improve paretic ankle function after stroke are therefore warranted. We have developed textile-based, soft wearable robots that transmit mechanical power generated by off-board or body-worn actuators to the paretic ankle using Bowden cables (soft exosuits) and have demonstrated the exosuits can overcome deficits in paretic limb forward propulsion and ground clearance, ultimately reducing the metabolic cost of hemiparetic walking. This study elucidates the biomechanical mechanisms underlying exosuit-induced reductions in metabolic power. We evaluated the relationships between exosuit-induced changes in the body center of mass (COM) power generated by each limb, individual joint power and metabolic power. Compared with walking with an exosuit unpowered, exosuit assistance produced more symmetrical COM power generation during the critical period of the step-to-step transition (22.4±6.4% more symmetric). Changes in individual limb COM power were related to changes in paretic (R2=0.83, P=0.004) and non-paretic (R2=0.73, P=0.014) ankle power. Interestingly, despite the exosuit providing direct assistance to only the paretic limb, changes in metabolic power were related to changes in non-paretic limb COM power (R2=0.80, P=0.007), not paretic limb COM power (P>0.05). These findings contribute to a fundamental understanding of how individuals post-stroke interact with an exosuit to reduce the metabolic cost of hemiparetic walking. Summary: A soft robotic exosuit designed to assist the paretic limb during walking can induce more symmetrical body center of mass power generation by the paretic and non-paretic limbs and reduce metabolic power consumption during hemiparetic walking.