Method and Apparatus for Detection of Bio-Aerosols
Aerosols of biological origin, whether formed intentionally or unintentionally, represent a potential threat of infection by pathogens. This threat is particularly daunting in the context of closed spaces, such as buildings. A variety of methods directed to identifying harmful biological materials are known. One of the known methods is based on the principles of the luminescence spectroscopy and is concerned with the production, measurement, and interpretation of electromagnetic spectra arising from either emission or absorption of radiant energy by various substances.
One aspect of the luminescence spectroscopy provides for the ability of biological materials to fluoresce due to the presence of proteins that possess certain amino acids. Fluorescence occurs when fluorophores and fluorescent particles absorb light at a given wavelength and then immediately emit light at a longer wavelength. Although not all particles fluoresce, some bio-aerosols contain intrinsic fluorophores that could potentially be used to tag the sample as a bioaerosol. Common fluorophores found in bioaerosol are, for example, Nicotinamide Adenine Dinucleotide (NADM), Tryptophan, Tyrosine, and Riboflavin. Each of these flurophores is characterized by respective peak excitation and corresponding emission wavelengths.
The primary fluorescent amino acids are tyrosine and tryptophan. The latter compound absorbs and emits at longer wavelengths and is less likely to have spectral overlaps with compounds that are not of a biological origin. However, there are still many environmental elements and hydrocarbons that will also fluoresce in the same wavelength as tryptophan, let alone the rest of the above-mentioned fluorophores.
Another aspect of the luminescence spectroscopy that may provide a tool for detecting biological materials is phosphorescence. As compared to fluorescence, phosphorescence is characterized by the time delay emission signal that allows for time-resolution to be used as a discriminator between samples that fluoresce versus those that phosphoresce. Hence, it is possible to delay the detection of the signal until after the light source has been extinguished and the fluorescent signal has disappeared. In addition to the time delay, Tryptophan phosphoresces at a longer emission wavelength.
Most of the known biological detectors incorporate fluorescence as a means for detecting the presence of a biological aerosol. Although fluorescence is a relatively simple approach, its major disadvantage, as discussed above, is the low selectivity for the bioaerosols of interest.
Current biological aerosol detection/triggering technology including the Biological Aerosol Warning Sensor (BAWS) developed by the Massachusetts Institute of Technology and the ultra Violet Aerodynamic Particle Sizer (UVAPS) developed by TSI is acceptable. However, these instruments are expensive, power hungry, large, and require complex algorithms to determine relatively little information.
A need, therefore, exists for a methodology either perfecting or complementing a fluorescence detection technique and for an inexpensive, low power, robust apparatus carrying out the inventive methodology.
One of the objects of the present invention is to provide a method for detecting pathogenic bioaerosols having a secondary detection technique to complement fluorescence.
Another object of the present invention is to provide an apparatus for carrying out the inventive method and capable of effectively collecting bioaerosols and selectively detecting the presence of the biological materials of interest contained in the bioaerosols.
Still another object of the present invention is to provide the inventive apparatus adapted to generate a warning upon detecting the biological materials of interest and to trigger secondary, more sophisticated, equipment for the confirmation of the initially detected materials and their further identification.
A further object of the present invention is to provide the inventive apparatus characterized by a simple, space- and cost-efficient structure.
Yet another object of the invention is to provide a detection system including multiple inventive apparatuses and deployed in a single location to provide added discrimination of actual threat levels.
These and other objects have been achieved by a new method, characterized by the collection of bioaerosols and further excitation of a sample thereof to controllably discriminate between biomaterials that fluoresce versus those that phosphoresce. The latter would indicate the probability of the presence of biological materials of interest in the excited sample.
The inventive method utilizes both fluorescence vs. fluorescence-based detection as well as fluorescence vs. phosphorescence-based detection. The optical system of the inventive sensor includes two optical channels both operative to detect fluorescence signals emitted at different wavelengths and associated with different bioagents. However, in addition to exclusively detecting fluorescence, one of the optical channels is also configured to detect phosphorescence after the detection of the fluorescence has been completed.
In the case of fluorescence vs. phosphorescence, if the former is detected by one of the optical channels, the possibility of the presence of a biomaterial of interest exists. Subsequent detection of the phosphorescence during the second stage indicates the probability of the presence of the biomaterial of interest. Since the inherent advantage of phosphorescence over fluorescence is the time delayed emission signal, the inventive apparatus is operative to allow for time-resolution to be used as a discriminator between samples that fluoresce versus those that phosphoresce. As a result, the two-stage inventive method maximizes the probability of detection and minimizes the number of false alarms.
In accordance with another aspect of the inventive method, a heavy atom perturber that has chemical affinity for association with the molecules, whose phosphorescence is desired, is bonded with the sampled material. As a consequence, if a biological agent to be detected is present in the sampled material, phosphorescence occurs at a known wavelength.
A further aspect of the present invention provides for an apparatus operative to carry out the inventive method. The inventive apparatus includes mechanical, optical, and electronic sub-systems controllably cooperating with one another to collect a sample of bioaerosol, optically excite it and electronically process emitted signals to detect the presence of the biomaterials of interest.
One of the advantages of the inventive apparatus is based on the characteristic of the phosphorescence to emit light waves at wavelengths after a light source has been extinguished. By configuring a two-channel optical system and providing an electronic processing unit with software, which executes on the processing unit, the desired sequence of mechanical, optical and electronic operations leading to the minimization of false alarms and the maximization of detection is established and maintained. This, of course, does not eliminate the possibility of simultaneously detecting different fluorescence intensities by both optical channels, only one of which is configured to detect phosphorescence in addition to the ability to detect fluorescence.
In accordance with a further aspect of the present invention, phosphorescence of the biomaterials of interest at room temperature is induced by controllably adding a heavy atom perturber to the sample in the presence of an oxygen scavenger. The latter is used to minimize the possibility of the fluorescence of non-biological materials. As a result, the apparatus can indicate the presence of the biomaterial of interest based on its phosphorescence without, however eliminating the detection of this material based on its fluorescence.
While the inventive apparatus can be used for a variety of purposes, desirably it can be associated with a plurality of identical apparatuses or sensors to provide a network operative to alert building, office and/or industrial site occupants of the presence of a potentially pathogenic bioaerosol. Simplicity of the inventive structure and its space-efficient configuration can be used to construct a warning system capable of generating a real time detection/information about bioagents of interest and of triggering a more sophisticated system to confirm and identify these bioagents.
Patent Status: U.S. patent(s) 7494769; 7830515 issued.
Ms. H. L. Curran
Phone: (443) 778-7262