Chang Yeol Lee

A Minimally Invasive Blood-Extraction System: Elastic Self-Recovery Actuator Integrated with an Ultrahigh- Aspect-Ratio Microneedle

A minimally invasive blood-extraction system is fabricated by the integration of an elastic self-recovery actuator and an ultrahigh-aspect-ratio microneedle. The simple elastic self-recovery actuator converts finger force to elastic energy to provide power for blood extraction and transport without requiring an external source of power. This device has potential utility in the biomedical field within the framework of complete micro-electromechanical systems.

Tower microneedle minimizes vitreal reflux in intravitreal injection

Intravitreal injection is widely used for easy control of drug levels in posterior segment of the eye by injecting the drug directly with hypodermic needles. Patients, however, often experience complications from intravitreal injection due to repeated injections, increased intraocular pressure, and infection. In addition, injected drug reflux after intravitreal injection makes it challenging to maintain predetermined drug dose due to the drug loss through backward effusions. Here, we described that the Tower Microneedle can reduce initial reflux and bleb formation due to its smaller outer diameter compared to a traditional hypodermic needle. Furthermore, we use phenylephrine hydrochloride for pupil expansion and demonstrated that Tower Microneedle induced similar pupil expansions using only half the drug volume, in the same period of time, compared to the 31 Gauge hypodermic needle. Consequently, Tower Microneedle achieves the same therapeutic effect in the vitreous body using fewer drugs than a traditional hypodermic needle due to the decreased backward drug effusion. Tower Microneedle described herein holds great promise for intravitreal injection with less reflux and lower drug dosage.

An Arched Micro-Injector (ARCMI) for Innocuous Subretinal Injection

Several critical ocular diseases that can lead to blindness are due to retinal disorders. Subretinal drug delivery has been developed recently for the treatment of retinal disorders such as hemorrhage because of the specific ocular structure, namely, the blood retinal barrier (BRB). In the present study, we developed an Arched Micro-injector (ARCMI) for subretinal drug delivery with minimal retinal tissue damage. ARCMIs were fabricated using three major techniques: reverse drawing lithography, controlled air flow, and electroplating. In order to achieve minimal retinal tissue damage, ARCMIs were fabricated with specific features such as a 0.15 mm−1 curvature, 45° tip bevel, 5 mm length, inner diameter of 40 µm, and an outer diameter of 100 µm. These specific features were optimized via in-vitro experiments in artificial ocular hemispherical structures and subretinal injection of indocyanine green in porcine eye ex-vivo. We confirmed that the ARCMI was capable of delivering ocular drugs by subretinal injection without unusual subretinal tissue damage, including hemorrhage.

Intravitreal injection of anti-vascular endothelial growth factor (anti-VEGF) antibody via Tower Microneedle

Tower Microneedle was developed with minimal ocular tissue damages even reflux, while no study was reported with intravitreal injection of ophthalmic drug via Tower Microneedle into the eye. Intravitreal injection of anti-vascular endothelial growth factor antibodies via the Tower Microneedle or a 30-G hypodermic needle was performed 1 week after argon laser irradiation into the retina of the mouse models. Less bleb formation was occurred with Tower Microneedle than 30-G hypodermic needle, while both needles led to comparable degrees of anti-angiogenesis in the retina after intravitreal injection of anti-vascular endothelial growth factor antibodies over 100 ng/μL concentration. Conclusively, the Tower Microneedle can deliver anti-vascular endothelial growth factor antibody into the posterior segment of the eye with minimal bleb formation after intravitreal injection.