MTD explains how micro-moulding is shaping the future of drug delivery
Solid performance: The advantages of micro-molding drug delivery components include improved dimensional stability, says MTD
An important movement within the medical device industry is poised to revolutionise 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 MTD Micro Molding is helping companies to achieve.
New advances in medical micro-moulding are creating solutions for a variety of drug delivery applications. As a result, many medical device companies are working with MTD to help set the new standard for manufacturing drug delivery components. It’s a development that could transform the market.
The advantages of micro-molding drug delivery components include:
- Improved dimensional stability
- Sharply reduced production costs
- Elimination of timely, costly and inaccurate assembly steps
Advanced micro-moulding will help forward-thinking medical device companies get their innovative products to market, forging a new path that competitors will likely follow.
Eliminating high-risk 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.
MTD worked with the company to define a possible solution: micro-moulding all the components together at once. Results of an initial mould 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, micro-moulding success was deemed possible.
MTD comments that advanced micro-moulding will help medical device companies get their products to market
The successful micro-moulding 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 micro-moulded 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, moulding the device as a single unit removed all possibilities for functional failures.
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 suited to being heat-formed but not good candidates for thin-wall moulding. 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. Next-generation products will likely follow the new advances that MTD is enabling by instead using polypropylene for cannula products. The fear of switching materials midstream, which involves a costly re-approval process, is common to many companies. With this customer however, the long-term savings far outweighed the cost of the approval process.
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 moulding machines are required to successfully mould a thin-walled cannula. This realisation — along with the determination that polypropylene was the better choice for the customer’s cannula application — meant MTD helped set a new standard that will revolutionise the POC drug delivery market.
Exact science: Precise tooling is the key to moulded parts with extremely small and complex geometries
Long-term, implantable 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 micro moulding: 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 micro-moulding this product to minimise 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 micro-moulded 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 1%. The key: using standardised equipment, customised to optimise IV loss. High-precision machines that are less abusive to sensitive materials enable extremely high control of critical processing parameters.
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 of ours who was unable to produce acceptable post-moulded IV, with loss averaging about 35%. 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%.
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 micro-moulding. 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 pharma companies to deliver drugs to the masses with ease.