Phased array ultrasound enhanced delivery of nano drugs for tendon adhesion treatment

Introduction: Over the decades, tendon adhesion has become a major health problem threatening the rehabilitation of patients after tendon surgery. Injury of the flexor tendon leads to rupture of the synovial sheath, which causes tendon exposure and adhesion with subcutaneous tissue. Current conservative therapies can promote chronic healing of tendon adhesion but have mixed success rates. Objectives: To reduce the degree of tendon adhesion, the need for a new non-invasive and accurate treatment method is substantial. Methods: A concave spherical ultrasonic phased array was fabricated by a fast 3D printing method. We generated a set of delayed square wave pulse sequences by Field Programmable Gate Arrays (FPGA) to excite the ultrasonic array, creating an ultrasonic focal area. Then we put flexor tendon phantoms, which were constructed by chitosan hydrogel and fibrous membrane using electrospinning, into the preset focal region and injected nano drugs in them. Finally, we measured the pulling force of tendon phantoms with a tensile tester. Results: The pulling force of three experimental groups were measured by a tensile tester. Compared to the "untreated group" (0.96 N), the phantom pulling force of the ultrasound + drug group" is 0.15 N, which is reduced by 85%. Furthermore, with the driving voltage increased from 5 V to 20 V, the pulling force can be reduced by 60%; with the duty ratio increased from 20% to 60%, the pulling force can be reduced by 50%; with treatment time increased from 1 min to 5 min, the pulling force can be reduced by 64%. Conclusion: Utilizing an ultrasonic array combined with nano drugs, our phase compensation control method can reduce the degree of tendon adhesion and hold a great implication for applications of rehabilitation treatment for postoperative patients. (c) 2023 Elsevier Ltd. All rights reserved.