Biomedical microdevices are fabricated on the order of one to hundred µm. These devices are fabricated with critical features and range in complexity from microchannels to microtranslucers and microelectromechanical systems (MEMS). Biomedical microdevices offers key advantages for applications in health i.e. they are extremely small in sizes; provides invasive procedures; have lower power consumption; high reproducibility and the low costs per device. In addition, they also offer better compatibility and multiple functionalities with integrating electronics.
This technology has proliferated the development of variety of microdevices such as micro components of pacemakers, micromedical devices, diagnostic devices, and drug delivery systems. This advent of technology has provided significant improvement over numerous chronic and no chronic illnesses. It has also transformed the way drugs are administered into the patients’ body. These microdevices are based on structural micro parts such as microchannels that stores drugs. In conjunction, MEMS devices incorporated with microacutuators, microsensors, and microtransducers improve the device capabilities.
Drug delivery through MEMS provides improved diagnosis, monitoring, and treatment of illness. It also has the ability to control the rate of drug released to the target area. Programmed with continuous delivery alongside the ability to release drug locally increases the treatment efficacy reducing systematic concentration levels and toxicity.
Drug delivery system can be classified into two types; passive and active.
Passive microdevices used for drug delivery do not rely on actuation mechanism. These devices are reservoir based and rely on mass transfer across permeable membrane to deliver drugs. The release rate of the drug can be controlled by:
- Effective permeability of membranes by fine-tuning material and structural dimensions
- Osmotic pressure
- Rate of degradation of polymer contained in the reservoir
- Diffusivity properties of the drug
One major thing to note here is that the delivery of the drug cannot be modified after implementation. Other passive release devices are based on internal body conditions like the pH or the temperature.
Passive Nanochannel-based Drug Delivery Devices
These devices were created to improve patient adherence towards chemotherapeutics and quality of life, eliminating the need for repeated administration and regular visits to the clinic. These control the release of the drug by physical-electrostatic confinement and are consist of 30 µm wide microchannels that connects the reservoir.
Clinical application- Diabetes, Melanoma, Prostate cancer
Active devices use different mechanisms to release drugs in the body and provide increased level of control. These devices can be customised to treat a wide range of diseases requiring specific drug delivery profiles. When compared, MEMS can be activated and can be stopped at any time after implantation. Common miniature power electronics are required by these active devices, which typically increases the overall form factor.
Electrothermally Actuated MEMS Drug Delivery Microchip
This type of device delivers drugs in a pulsatile manner and because of such, several works on active drug delivery devices based on MEMS have made substantial progress towards treating ailments.
Clinical application – Osteoporosis
Rapid-delivery Microchip for Acute Clinical Conditions
This device consists of a membrane, actuation, and reservoir layer. Membrane layer consists of biocompatible silicon nitrate and the actuation layer of three micro resistors. On passage of current through resistors, heat is generated and increases the inside pressure of the reservoir. This lead to the rupture of silicon nitrate membrane, followed by the release of the drug.
Clinical application- Hemorrhagic Shock
Magnetically Control MEMS Delivery
A magnetic MEMS drug delivery device was developed for the controlled release of chemotherapeutic agent. In this device, pressure in the reservoir is built, enabling the drug to diffuse out.
Clinical application- Cancer
Some other devices are Micropump MEMS-based drug delivery system; Transfermall MEMS; Microneedle Patch Array Delivery System; Electrothermal MEMS drug delivery Device; Microfuluidic Hydraulic MEMS-based devices.
The next generation of delivery models are present in today’s inter-connected world. The current development of such delivery systems is at early stage and even some technologies are still in conception phase. From clinical standpoint, if such clinical needs do exist and is identified, many such applications will demand large payload that cannot be accommodated within the microdevices. Passive and active devices can be a part of invasive procedures and have the ability to enhance the efficacy while reducing the toxicity of the drug. These devices offer a wide range of application with tailored local release and high adherence prerequisites. They also represent a novel technology but also face different regulatory challenges. They also represent the next generation of platforms for more accurate and efficient drug delivery. Such novel platforms promise the patients to increase adherence and overall better treatment outcomes.