· Universal Balloon Medical · Articles · 4 min read · Reviewed by the Universal Balloon Medical engineering team
How Drug-Coated Balloons Are Coated: Ultrasonic Spray Coating Explained
Drug-coated balloons live or die by coating uniformity. This guide explains how DCBs are coated, compares the main coating methods, and shows why ultrasonic spray coating is used for consistent drug dose and transfer.
In short
A drug-coated balloon (DCB) carries an antiproliferative drug plus an excipient on its surface; when inflated, the drug transfers to the vessel wall and the balloon is removed — "leave nothing behind." Coating uniformity governs drug dose, transfer efficiency and coating integrity, so most DCB lines move from dip or pipette coating to ultrasonic spray coating, which atomizes the drug solution into fine, even droplets for a thin, repeatable layer.
Drug-coated balloons promise a simple idea: deliver a therapeutic drug to a vessel wall and leave nothing behind. Delivering that reliably, at scale, comes down to one thing above all — how evenly the drug is coated onto the balloon. This guide explains what a DCB is, why coating uniformity is the make-or-break quality attribute, and how the main coating methods compare.
What is a drug-coated balloon?
A drug-coated balloon (DCB) is a balloon catheter whose outer surface carries an antiproliferative drug — commonly paclitaxel, or increasingly a -limus (sirolimus family) — combined with an excipient (a carrier such as a hydrophilic spacer). During a short inflation at the lesion, the drug transfers from the balloon surface into the vessel wall, where it inhibits the cell proliferation that causes restenosis. The balloon is then deflated and withdrawn.
That is the key difference from a drug-eluting stent (DES): a DCB leaves no permanent implant behind — the “leave nothing behind” approach — which is why DCBs are widely used in small vessels, bifurcations and in-stent restenosis.
Why is coating uniformity so important?
Everything clinically meaningful about a DCB traces back to the coating:
- Dose consistency — uneven coating means some units carry too much drug and some too little.
- Transfer efficiency — the fraction of drug that actually reaches the vessel wall depends on an even, intact coating and the right excipient.
- Coating integrity — a coating that cracks or sheds releases particulate downstream, a safety concern; it must adhere through folding, tracking and inflation.
- Material economy — the active drug is expensive, so overspray and waste matter commercially.
In short, coating weight and thickness uniformity is the critical quality attribute a DCB line is built to control.
How are drug-coated balloons coated?
The drug and excipient are formulated into a coating solution, applied to the balloon, and dried. There are three common application methods:
| Method | How it works | Trade-offs |
|---|---|---|
| Dip coating | The balloon is dipped into the coating solution. | Simple, but hard to control thickness and uniformity; more waste. |
| Pipette / metered dispense | A measured volume is dispensed onto the rotating balloon. | Good dose metering per unit; slower; uniformity depends on spreading. |
| Spray coating | The solution is atomized and sprayed onto the rotating balloon. | Even layers, scalable; conventional air spray can overspray. |
| Ultrasonic spray | An ultrasonic nozzle atomizes the solution into fine, uniform droplets. | Best thickness uniformity, low overspray, precise low-flow control. |
Balloons may be coated folded or unfolded depending on the formulation and transfer strategy, and the drying step (temperature, airflow, time) is tuned so the coating sets without cracking.
What is ultrasonic spray coating, and why use it?
An ultrasonic spray nozzle uses a piezo element vibrating at high frequency to break the coating solution into a soft, low-velocity mist of very fine, uniform droplets. Because the droplets are small and consistent and the spray is gentle, the result is a thin, even film with:
- Tight thickness and coating-weight uniformity, critical for dose consistency.
- Low overspray and drug waste — important given the cost of the active ingredient.
- Precise control at low flow rates, so even small, narrow-window doses are repeatable.
This is why ultrasonic spray is the method of choice on most modern DCB lines, and the principle behind the Balloon Ultrasonic Coating System (UBM-USS-1000).
Coating is one step in a chain
Coating does not stand alone. The forming step sets the balloon surface the coating lands on; folding and crimping must not crack or redistribute the coating; and inspection should verify coating presence, coverage and surface integrity. Treating coating as part of a connected, in-line, traceable process — with coating weight logged per unit — is what turns a good coating method into consistent DCB yield.
Building or upgrading a drug-coated balloon line? Talk to our engineering team about coating uniformity, drying and in-line verification.
Key takeaways
- A DCB combines a drug (often paclitaxel or a -limus) with an excipient carrier that helps the drug release and cross into the vessel wall on contact.
- Coating uniformity is the critical quality attribute: it drives dose consistency, transfer efficiency, drying behaviour and coating integrity (minimizing particulate loss).
- The main coating methods are dip coating, metered pipette/dispense coating, and spray coating; ultrasonic spray is the spray variant prized for fine, uniform, low-overspray droplets.
- Ultrasonic spray coating gives tight control of coating weight and thickness at low flow rates, which matters when the active drug is expensive and the dose window is narrow.
- Coating is one step in a chain — forming, folding and inspection all interact with it, so coating weight and surface integrity should be verified in-line and logged for traceability.
Frequently asked questions
What is a drug-coated balloon (DCB)?
A drug-coated balloon is a balloon catheter whose surface carries an antiproliferative drug combined with an excipient. During a short inflation, the drug transfers to the vessel wall to inhibit restenosis, then the balloon is withdrawn — unlike a drug-eluting stent, no implant is left behind.
How are drug-coated balloons coated?
The drug and excipient are formulated into a coating solution and applied to the balloon surface, then dried. Application is done by dip coating, metered pipette/dispense coating, or spray coating. Ultrasonic spray coating is widely used because it produces fine, uniform droplets for a thin, even and repeatable layer.
Why is coating uniformity so important for DCBs?
Because it determines how much drug is delivered and how evenly. Non-uniform coating means inconsistent dose, poor or uneven transfer to the vessel wall, and a higher risk of coating cracking or shedding as particulate. Uniform coating weight and thickness are the key quality attributes a DCB line controls.
What is ultrasonic spray coating and why use it?
An ultrasonic nozzle vibrates at high frequency to atomize the coating solution into a soft, low-velocity mist of very fine, uniform droplets. Compared with air-atomized spray or dip coating, it gives better thickness uniformity, less overspray and waste of expensive drug, and precise control of coating weight at low flow rates.
