On-Demand Drug Release from Click-Refillable Drug Depots

Loading Intracranial Drug-Eluting Reservoirs Across the Blood-Brain Barrier With Focused Ultrasound

OBJECTIVE

Efficient, sustained and long-term delivery of therapeutics to the brain remains an important challenge to treatment of diseases such as brain cancer, stroke and neurodegenerative disease. Focused ultrasound can assist movement of drugs into the brain, but frequent and long-term use has remained impractical. Single-use intracranial drug-eluting depots show promise but are limited for the treatment of chronic diseases as they cannot be refilled non-invasively. Refillable drug-eluting depots could serve as a long-term solution, but refilling is hindered by the blood-brain barrier (BBB), which prevents drug refills from accessing the brain. In this article, we describe how focused ultrasound enables non-invasive loading of intracranial drug depots in mice.

METHODS

Female CD-1 mice (n = 6) were intracranially injected with click-reactive and fluorescent molecules that are capable of anchoring in the brain. After healing, animals were treated with high-intensity focused ultrasound and microbubbles to temporarily increase the permeability of the blood-brain barrier and deliver dibenzocyclooctyne (DBCO)-Cy7. The mice were perfused, and the brains were imaged via ex vivo fluorescence imaging.

RESULTS

Fluorescence imaging indicated small molecule refills are captured by intracranial depots as long as 4 wk after administration and are retained for up to 4 wk based on fluorescence imaging. Efficient loading was dependent on both focused ultrasound and the presence of refillable depots in the brain as absence of either prevented intracranial loading.

CONCLUSION

The ability to target and retain small molecules at predetermined intracranial sites with pinpoint accuracy provides opportunities to continuously deliver drugs to the brain over weeks and months without excessive BBB opening and with minimal off-target side effects.

Reaching new lights: a review on photo-controlled nanomedicines and their in vivo evaluation

The selective and efficient delivery of bioactive molecules to sites of interest remains a formidable challenge in medicine. In recent years, it has been shown that stimuli-responsive drug delivery systems display several advantages over traditional drug administration such as an improved pharmacokinetic profile and the desirable ability to gain control over release. Light emerged as one of the most powerful stimuli due to its high biocompatibility, spatio-temporal control, and non-invasiveness. On the road to clinical translation, various chemical systems of high complexity have been reported with the aim to improve efficacy, safety, and versatility of drug delivery under complex biological conditions. For future research on the chemical design of such photo-controlled nanomedicines, it is essential to gain an understanding of their in vivo translation and efficiency. Here, we discuss photo-controlled nanomedicines that have been evaluated in vivo and provide an overview of the state-of-the-art that should guide future research design.

Biomaterial-targeted precision nanoparticle delivery to the injured spinal cord

Drug delivery requires precision in timing, location, and dosage to achieve therapeutic benefits. Challenges in addressing all three of these critical criteria result in poor temporal dexterity, widespread accumulation and off-target effects, and high doses with the potential for toxicity. To address these challenges, we have developed the BiomatErial Accumulating Carriers for On-demand Nanotherapy (BEACON) platform that utilizes an implantable biomaterial to serve as a target for systemically delivered nanoparticles (NPs). With the BEACON system, administered NPs are conjugated with a ligand that has high affinity for a receptor in the implanted biomaterial. To test BEACON, an in vivo spinal cord injury (SCI) model was used as it provides an injury model where the three identified criteria can be tested as it is a dynamic and complicated injury model with no currently approved therapies. Through our work, we have demonstrated temporal dexterity in NP administration by injecting 6 days post-SCI, decreased off-target accumulation with a significant drop in liver accumulation, and retention of our NPs in the target biomaterial. The BEACON system can be applied broadly, beyond the nervous system, to improve systemically delivered NP accumulation at an implanted biomaterial target. STATEMENT OF SIGNIFICANCE: Targeted drug delivery approaches have the potential to improve therapeutic regimens for patients on a case-by-case basis. Improved localization of a therapeutic to site of interest can result in increased efficacy and limit the need for repeat dosing. Unfortunately, targeted strategies can fall short when receptors on cells or tissues are too widespread or change over the course of disease or injury progression. The BEACON system developed herein eliminates the need to target a cell or tissue receptor by targeting an implantable biomaterial with location-controllable accumulation and sustained presentation over time. The targeting paradigm presented by BEACON is widely applicable throughout tissue engineering and regenerative medicine without the need to retool for each new application.