An optical technology has been developed that can determine the quantity and size of particles in liquid or air, and simultaneously determine whether each particle is inert or biologic, all in real time. The technology, developed by BioVigilant, provides instantaneous microbial detection, thereby creating wide-ranging and profound positive consequences for pharmaceutical manufacturers.

This article briefly discusses the problems this technology solves, how the technology works, and how it is applied.

How It’s Done Now and the Consequences
For both internal and regulatory reasons within the pharmaceutical manufacturing environment, it is required that testing be performed in order to determine the level of microbial contamination. Existing conventional testing methods, however, all have several undesirable attributes in common:
 

• The cost per test is high;
• The process is labor intensive often requiring significant set-up, monitoring, and counting;
• The process is episodic and slow, with results generally not available for two to five days.

Among these undesirable attributes, the consequences of waiting for results are generally the most significant, and include costly planned and unplanned halts in production, as well as continued production under incorrectly assumed to be acceptable conditions and finding out later that, in fact, the conditions were not within regulatory or internal requirements. This can then result in product being thrown out, as well as make it required that expensive and time-consuminginvestigations be conducted.

The Technology
The technology was originally developed to meet the demanding specifications of the U.S. Military and Homeland Security for real time detection of the presence of airborne weaponized bio-agents such as Bacillus anthracis, which is in the size range of 1 to 7 microns. After considering the technical requirements and analyzing the suitability of existing technology for particle detection and sizing (much of which was invented 20 or more years ago), it was decided that the existing methods contained fundamental design limitations that would keep the development company from accomplishing its task. A new approachwith a fundamentally different design was required.

Using an innovative optical design, a method was invented to count and size very small particles to a sensitivity level and at lower costs not possible using existing technology. As an additional benefit, this new technology allowed the concurrent determination for each individual particle, identifying it as inert or biologic. In addition to its application within homeland security, this combination of technologies is now being applied to the field of pharmaceutical manufacturing. The following is a brief description of fluorescence sensor technology developed with regard to airborne monitoring (liquid monitoring is very similar), using an IMD-A detector. (The model IMD-A signifies “Instantaneous Microbial Detector–Air”. A similar product IMD-L was also developedwhere “L” represents liquid.)

The IMD-A consists of three components: (1) an optical assembly to measure individual particle size; (2) a concurrent optical assembly to detect a UV laser-induced fluorescence signal from certain metabolites inside microbial cells and spores; and (3) an algorithm for differentiating airborne microbes from inert dust particles.

The optical assemblies use the well-known and often used Mie scattering detection scheme [1], but apply it in a novel way, enabling the devices to make highly accurate measurements of airborne particles with size ranges from 0.5 microns to 20 microns. This capability to make fine distinctions in size is important in order to determine the class of microbe, since different classes of microbes have different size ranges, as shown in Figure 1.

The technology’s unique use of Mie scattering also facilitates the use of UV light illumination, to concurrently examine each particle for the presence of the metabolites NADH and riboflavin, which are necessary intermediates for metabolism of living organisms, and therefore exist in microbes such as bacteria and fungi. If these chemical compounds exist in a bio-aerosol, they are excited by the UV photon energy and subsequently emit auto-fluorescence light which is detected by the IMD-A. While the technology is not capable of identifying the genus or species of microbes, and viruses are too small and lack the metabolism for detection, the ability to simultaneously, and for each particle, determine the size of the particle and if it is biologic or inert, indicates to the user the presence or absence of microbial contamination.

Figure.1. Particle size ranges of several airborne inert and microbial particulates

How Microbial Detection Devices Can Be Applied to Pharmaceutical Manufacturing

The IMD-A and IMD-L devices can be used in pharmaceutical manufacturing cleanrooms as (I) warning devices; (II) as continuous monitoring and trending devices; and, (III) to verify if remediation was successful.