Medical practitioners have been using needles to inject medicines into human bodies for decades. But no one likes getting pricked, be it children or adults. In some cases, the fear is so strong, especially in children, that many miss out on vaccinations and other medical treatments. For patients who have diabetes, the stress is even greater as they may require frequent insulin injections.
As a relief to patients, a team of researchers led by Prof. Viren Menezes from the Department of Aerospace Engineering at the Indian Institute of Technology Bombay (IIT Bombay) has now worked a way around to deliver drugs without needles by developing a shock syringe. In their study published in the Journal of Biomedical Materials & Devices, the IIT Bombay researchers compared the effectiveness of drug delivery by a shock syringe versus a regular needle on laboratory rats.
Unlike syringes with needles, the shock syringe doesn’t rely on piercing the skin with a sharp tip. Instead, it uses high-energy pressure waves (shock waves) that can travel faster than the speed of sound to pierce the skin. These waves, when generated, compress the surrounding medium (such as air or liquid) through which they travel. A similar effect happens during a sonic boom; when an aircraft flies faster than the speed of sound, it creates shock waves that push and disturb the air.
The shock syringe, developed earlier in 2021 in Prof. Menezes’ lab, is slightly longer than a regular ballpoint pen. The device has a micro shock tube consisting of three sections: the driver, driven, and drug holder, which work together to create the shockwave-driven microjet for drug delivery. Pressurised nitrogen gas is applied to the shock syringe (driver section of micro shock tube part) filled with liquid drugs to create a microjet of the drug. The microjet travels at a speed nearly twice as fast as a commercial aeroplane at takeoff. This jet stream of liquid drug passes through the nozzle of the syringe before penetrating the skin. The entire process of delivering drugs using a shock syringe is rapid and gentle; most patients wouldn’t feel a thing.
“The shock syringe is designed to deliver the medication rapidly. However, if a regular syringe is inserted too quickly or with excessive force, it can cause unnecessary trauma to the skin or underlying tissues,” remarks Ms. Priyanka Hankare, research scholar and lead author of both studies.
To minimise tissue damage and ensure consistent and precise drug delivery, the pressure in the shock syringe is continuously monitored and
“rigorous testing on tissue simulants (such as synthetic skin) helps to calibrate the force and speed of jet insertion, ensuring safety and comfort,” Ms. Hankare points out.
Additionally, the researchers have optimised the nozzle design to have an opening of just 125 μm (roughly the width of a human hair).
“This ensures it is fine enough to reduce pain during insertion but strong enough to handle the mechanical forces needed for quick deployment of microjet,” adds Ms. Hankare.
To test how efficiently the shock syringe delivers the medication, the researchers conducted three different tests in which they injected three different types of drugs into the rats. Researchers measured the drug levels in the blood and tissues to monitor drug distribution and absorption in the body using the high-performance liquid chromatography (HPLC) method.
When an anaesthetic (Ketamine-Xylazine) was injected through the skin of the rats for the tests, the shock syringe achieved the same effect as needles. In both cases, the anaesthetic effect started three to five minutes after injection and lasted up to 20-30 minutes. This proves the suitability of the shock syringe for drugs that require slow and sustained release. For viscous drug formulations, such as an antifungal (Terbinafine), the shock syringe outperformed regular needles. The rat skin samples showed that the shock syringe deposited more terbinafine deeper into the skin layers than needle delivery. When insulin was administered to diabetic rats, the researchers observed that the blood sugar levels were lowered effectively and maintained at the lower level for a longer time when using a shock syringe compared to needles.
What’s more, when researchers performed tissue analysis on the rats, it revealed that the shock syringe caused less damage to the rat’s skin than syringes. As shock syringes cause less inflammation, they allow the wound at the injection spot to heal much faster.
The development of a shock syringe promises more than pain-free injections. It could make immunization drives quicker and more efficient for both children and adults. It could prevent the occurrence of bloodborne diseases caused by needle-stick injuries due to mishandling or improper disposal.
Furthermore, “Shock syringes are designed to perform multiple drug delivery shots (e.g., over 1000 shots tested), offering reliability and cost-effectiveness over time at the expense of nozzle replacement,” explained Ms. Hankare.
Although the future of shock syringes looks good,
“its potential to transform drug delivery in clinical environments will depend on several factors, such as further innovation for human use, regulatory approval, and affordability and accessibility of the device,” concludes Ms. Hankare.
This project has received funding and support from the HDFC ERGO—IIT Bombay Innovation Lab, a partnership between HDFC ERGO General Insurance Company Ltd. and IIT Bombay.