Wearable and implantable devices for drug delivery: Applications and challenges

Poor adherence to drug dosing schedule is responsible for ∼50% of hospitalization cases. Most patients fail to adhere to a strict dosing schedule due to invasive drug administration, off-target toxicities, or medical conditions like dementia. The emerging concept of wearable devices (WDs), implantable devices (IDs) and combined wearable and implantable devices (WIDs) for drug delivery has created new opportunities for treating patients with chronic diseases needing repeated and long-term medical attention like diabetes, ocular disorders, cancer, wound healing, cardiovascular diseases, and contraception. WDs, worn on the body surface have created appealing non-invasive, self-administrable drug delivery platforms which receive huge patient compliance. Microneedle-skin patches, wound healing patches, drug-eluting contact lenses, mouth guards, intra-vaginal rings, pharmaceutical jewelry, and drug-loaded self-care textiles are popular WDs explored in drug delivery. In contrast, IDs are surgically placed inside body tissue allowing higher payload and enhanced localized effect for an extended duration. Hormone micropumps, hydrogel/nanofibrous depot, coronary stents, intravitreal devices, and intrauterine devices are some representative examples of IDs. In this review, we have described the past 10 years of research progress on drug-delivering WDs and IDs in the context of treating diseases that demand repeated and long-term medication, especially those affecting soft tissues. We highlighted several technical challenges that need to be addressed before considering the translation of such technologies to clinics.