Micromolding Is Shaping the Future of Drug Delivery

An important movement within the medical device industry is poised to revolutionize the point-of-care (POC) drug delivery market. The goal at hand—making drug delivery devices more convenient, painless, and effective for patients—is one that micromolding companies are helping companies to achieve.

New advances in medical micromolding are creating solutions for a variety of drug delivery applications. As a result, many medical device companies are working with suppliers to help set the new standard for manufacturing drug delivery components. It’s a development that could transform the market.

The advantages of micromolding drug delivery components include:

Improved dimensional stability
Sharply reduced production costs
Elimination of timely, costly, and inaccurate assembly steps

Advanced micromolding can help forward-thinking medical device companies get their innovative products to market, forging a new path that competitors will likely follow.

Eliminating High-Risk, Cumbersome Assembly Steps

An injectable drug delivery systems company was struggling with the traditional manufacturing methods for its drug delivery device. The process included a series of high-risk, cumbersome steps to manually assemble four micro components to combine the cannula and housing. Cost concerns were also a factor, as these steps required having an entire room of people assembling components at one time.

Fig. 1 – An example of a polypropylene, thin-walled, micromolded part in the form of a micro-pipette tip. The micro-sized tip creates micro droplets dispensed from the nozzle, ideal for numerous applications in laboratory analytics, pharmaceuticals, drug delivery, and miniature surgical devices. The key feature is a 60- micron diameter (0.0024

In this case, MTD Micro Molding worked with the company to define a possible solution: micromolding all the components together at once. Results of an initial mold flow analysis showed this was a feasible approach. Surprised at the results, MTD performed a second analysis to be sure. In parallel, the customer had an analysis performed as well. Sure enough, micromolding success was deemed possible.

The successful micromolding of this device eliminated three assembly steps (which had been assumed to be required as the industry norm) and created huge cost savings for the customer. The geometry-rich cannula was micromolded at $0.10 a unit, in contrast with making four separate components at a cost of over $1.50 for the set (excluding assembly costs). In addition, with the assembly steps largely contributing to the main failure mode in the final device, molding the device as a single unit removed all possibilities for functional failures. (See Figure 1)

Most manufacturers of similar cannula components use fluoropolymers, a common method for converting an extrusion into a heat-formed product. However, this process is very expensive and has a high fallout rate.

Fluoropolymers are known for chemical resistance, lubricity, and heat resistance, but are shear-sensitive. Because of those properties, they are uniquely suited for being heat-formed but not good candidates for thin-wall molding. Polypropylene is a material that has great chemical resistance and lubricity, and is not shear-sensitive. While polypropylene cannot be heat-formed, it does offer much better melt flow in thin-walled applications, such as cannulas.

Traditional manufacturing methods for the development of cannulas have used the heat-forming process of converting fluoropolymer extrusions to cannulas. Nextgeneration products will likely follow these advances by using polypropylene for cannula products. The fear of switching materials midstream, which involves a costly reapproval process, is common to many companies. With this customer, however, the long-term savings far outweighed the cost of the approval process.

Fig. 2 – A polypropylene, thin-walled, micromolded part with a 0.005

In terms of technical execution, it is extremely difficult to make a long, thin, straight part such as a cannula. The challenge lies in the fact that for a 0.005" wall thickness to flow long-distance, a tiny, delicate core pin must be centered precisely in the cavity. With long length of thin flow, if material flow becomes uneven, it is impossible to fill an annular ring. When flow becomes unbalanced, a hydraulic effect is created on one side and pushes the core pin, which produces an ultra-thin wall on the opposite side. This, in turn, causes fill problems and distortion.

Precise control over the position of the core is critical, which is why highly capable tooling and molding machines are required to successfully mold a thin-walled cannula. This realization—along with the determination that polypropylene was the better choice for this customer’s cannula application—meant helping to set a new standard for the point of care drug (POC) delivery market. (See Figure 2)

Long-Term, Implantable Drug-Eluting Products

There is a movement in the market to reduce office visits for pain management and make infrequent scheduled procedures for degenerative diseases the norm. We have seen two examples of these types of products that were improved with micromolding: one-time use applications and permanent refillable applications.

One-Time Use Applications

A customer came to MTD with a time-release pharmaceutical application to treat macular degeneration consisting of an active drug compounded with a bioabsorbable material that gets implanted inside the eye. The carrier dissolves, delivering the drug over an extended period of time.

This painless procedure is a welcome alternative to the typical treatment of needle injections into the patient’s eye every 30 days. Like the cannula company, this customer began with extrusion to create its product, which it perceived to be the only solution. The extrusion process produced a high level of active drug loss, however. MTD was approached to attempt micromolding this product to minimize active drug loss and improve dimensional stability.

This project also had other interesting challenges. With test batches of the compounded material containing the active drug costing about $1 million per kilogram, conservation and proper handling of the material was critical. Also, maintaining the extremely tight tolerances of the critical dimensions was critical to the product’s function because the amount of material that made up the part was directly related to the drug dosage.

Dimensional control for such a tiny micromolded component (about one-third the size of a grain of rice) required highly precise molding equipment, which MTD specially purchased for the job. The first shot samples revealed stable critical dimensions and almost undetectable active drug loss at about one percent. The key: using standardized equipment, customized to optimize IV loss. High-precision machines that are less abusive to sensitive materials enable extremely high control of critical processing parameters. (See Figure 3)

Fig. 3 – Precise tooling is the key to molded parts with extremely small and complex geometries by creating detail that otherwise is not possible, such as mirror-smooth finishes with perfectly detailed corners, edges, and surfaces.

Other emerging “patient comfort” applications that are coming to light are drug delivery devices for chronic illnesses like sinusitis, an inflammation of the tissue lining the sinuses. This bioabsorbable device, used after surgery, is coated with an anti-inflammatory drug and releases the drug over a period of time. It is a superior alternative to revision surgeries that are typically required for chronic sinusitis, for which there is no cure, or daily oral medications.

This customer came to MTD after working with a competitor who was unable to produce acceptable post-molded IV, with loss averaging about 35 percent. The critical features (multiple micro through-holes) of the bioabsorbable component were also unable to be dimensionally controlled with the previous supplier. This caused many issues in the secondary manual assembly step. The first shots MTD produced for the customer revealed crisp features, capable critical dimensions, and IV loss of 3.4 percent.

Permanent Refillable Applications

Permanent drug-eluting products are a better option for certain applications.

One emerging device is an assembly of parts that is inserted into the body and slowly releases a drug over time, which is less shocking to the patient’s system. Providing a novel approach to delivering drugs, this device includes a porous delivery port, drug chamber, and silicone seal. The drug chamber is a rechargeable well with a 0.0035" wall thickness; this thin wall is important to maintain the highest volume of drug for a very small space. The well-like device is implanted once, weeps out a refillable drug from a reservoir, and is refillable via infrequent injections.

A Final Word

The marketplace for POC drug delivery is expanding. The ability to produce cannulas with extremely thin walls as well as ultra-precise drug delivery components that historically have not been able to be molded is the key to this development.

When the question becomes, “How can we make things smaller and the fluid path more precise?” the answer clearly leads to micromolding. The movement to provide more convenient, painless, and effective drug delivery devices to patients is pushing the most innovative and forward-thinking companies to break the paradigm of what drug delivery devices can be. These companies are thinking outside the box while solving patients’ problems with new tools. The result is drug delivery devices that create a whole new platform for pharmaceutical companies to deliver drugs to the masses with ease.

This article was written by Lindsay Mann, Project Manager, MTD Micro Molding, Charlton, MA. For more information, Click Here . BIOMEDevice Boston, Booth 442; MD&M East, Booth 875