New SMA/PMMA alloy developed for point-of-care diagnostic devices

Point-of-care (POC) testing is a rapidly growing segment of the in vitro diagnostics sector, as it provides test results in minutes rather than days or even weeks. Not only does it improve the patient experience in developed economies but it brings a life-saving technology to countries with limited healthcare infrastructures. POC testing typically relies on microfluidic instruments, and Polyscope Polymers B.V. (Geleen, Netherlands) has developed an engineering thermoplastic alloy that combines the benefits of styrene maleic anhydride (SMA) and polymethyl methacrylate (PMMA) and reportedly improves on the materials currently in use. The Xiloy SO2315 SMA/PMMA alloy offers excellent optical properties; biocompatibility with a variety of proprietary coatings, reagents, and blood and tissue products; and high dimensional stability, according to the company.

The material is being used in devices that are currently undergoing regulatory review and will be on the market soon, said Polyscope.

Polyscope Polymers microfluidic device

POC diagnostic devices are small, often handheld, instruments that are used to diagnose and monitor various diseases and conditions in primary-care locations such as doctor's offices, hospitals or patient homes. In just a few minutes, medical personnel and patients have test results back compared with the days and even weeks of waiting for results when samples are sent to external test labs. POC devices are part of a trend in new medical technologies that aim to lower healthcare costs while improving patient outcomes.

Material matters in POC test devices

Microfluidic chips are a key element in delivering accuracy and speed in POC test devices. Molded from transparent thermoplastics, the disposable cassettes feature functional substrates that are modified for surface reactivity and must incorporate 50- to 100-µm-wide molded micro-channels for routing tiny amounts of human fluids as well as reagents for diagnostic tests. Polystyrene (PS) and cyclic olefinic copolymer (COC) currently are used to mold the disposable cassettes, but each material has its challenges, according to Polyscope. While PS offers good transparency, it lacks inherent surface reactivity, which necessitates a post-mold functional coating step, adding cost and time. As for COC, it is a fairly new polymer and is expensive.

Polyscope’s SMA and PMMA alloy offers a number of advantages for molding microfluidic cassettes, according to the company. The specific reactivity of anhydride groups on the SMA portion of the Xiloy SO2315 copolymer has the intrinsic capability to react with the “bioanchor,” which captures and binds to analytes in the fluid sample. This simplifies the post-mold coating process while making the device more robust. SMA also provides higher thermal stability than PS for tests requiring heat to process samples, plus it maintains dimensional stability to ensure that the micro channels operate properly and that cassettes fit into test devices.

Because SMA is not especially miscible with PS, chemists tend to combine it with PMMA, which provides transparency for optical detection test methods and has biological compatability with human tissue and fluids. The resulting copolymer is chemically compatible with the proprietary coatings and reagents typically used on microfluidic cassettes. It also processes easily and maintains consistent tight dimensions for intricate molded micropatterns that are critical for accurate and reliable rest results.

The global point-of-care molecular diagnostics market is anticipated to reach $3.86 billion by 2024, expanding at a compound annual growth rate of 14.4%, according to a study published by Grand View Research in May 2019. Initially focused on screening for infectious disease in developing countries, POC testing has expanded at a rapid pace over the past decade, with devices available or under development for cardiology, oncology and hematology testing, writes Grand View Research.

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