| Id |
Subject |
Object |
Predicate |
Lexical cue |
| T671 |
0-28 |
Sentence |
denotes |
3.2 Sample handling formats |
| T672 |
29-106 |
Sentence |
denotes |
The sample handling format is highly influenced by the biosensor application. |
| T673 |
107-262 |
Sentence |
denotes |
As discussed in further detail in the following sections, pathogens are present in liquid and solid matrices and on surfaces (e.g., of biomedical devices). |
| T674 |
263-421 |
Sentence |
denotes |
In addition, pathogens can be aerosolized, which is a significant mode of disease transmission associated with viral pathogens (e.g., influenza and COVID-19). |
| T675 |
422-511 |
Sentence |
denotes |
Sample handling formats can be generally classified as droplet-, flow-, or surface-based. |
| T676 |
512-619 |
Sentence |
denotes |
Droplet formats involve sampling from a larger volume of potentially pathogen-containing material or fluid. |
| T677 |
620-753 |
Sentence |
denotes |
The sample droplet is subsequently analyzed by deposition on a functionalized transducer or transferred to a fluidic delivery system. |
| T678 |
754-937 |
Sentence |
denotes |
For example, Cheng et al. created an electrochemical biosensor based on a nanoporous alumina electrode tip capable of analyzing 5 μL of dengue virus-containing solutions (Cheng et al. |
| T679 |
938-944 |
Sentence |
denotes |
2012). |
| T680 |
945-1061 |
Sentence |
denotes |
Droplet formats are simplistic sample handling formats and have the advantage of being performed by unskilled users. |
| T681 |
1062-1199 |
Sentence |
denotes |
While dropletformats have been extensively used with colorimetric biosensors, they have also been adapted for electrochemical biosensors. |
| T682 |
1200-1293 |
Sentence |
denotes |
For example, commercially-available blood glucose meters use a droplet format (Vashist et al. |
| T683 |
1294-1300 |
Sentence |
denotes |
2011). |
| T684 |
1301-1453 |
Sentence |
denotes |
Examples of low-cost, paper-based, or disposable electrochemical biosensors for pathogen detection that utilize droplet formats are provided in Table 1. |
| T685 |
1454-1642 |
Sentence |
denotes |
For example, Zhao et al. created a screen-printed graphite-based electrode for electrochemical detection of Vibrio parahaemolyticus (V. parahaemolyticus) based on 5 μL samples (Zhao et al. |
| T686 |
1643-1649 |
Sentence |
denotes |
2007). |
| T687 |
1650-1956 |
Sentence |
denotes |
However, while droplet formats minimize the technical and methodological barriers to measurement, such as eliminating the need for physical systems associated with biosensor housing and sample handling, they can exhibit measurement challenges associated with mass transport and target sampling limitations. |
| T688 |
1957-2255 |
Sentence |
denotes |
One of the most critical considerations associated with application of droplet formats to pathogen detection is sampling, specifically if sufficient sampling has been performed on the system for which bioanalytical information is desired (e.g., a human, a food source, or source of drinking water). |
| T689 |
2256-2516 |
Sentence |
denotes |
For example, the rationale that the bioanalytical characteristics of a droplet represent that of the bulk system is sound only in a well-mixed system, specifically, a system that exhibits a uniform spatial distribution of species (i.e., concentration profile). |
| T690 |
2517-2754 |
Sentence |
denotes |
We note that while this is typically the case for samples acquired from closed, convective systems, such as body fluids, it should be challenged when considering open systems that exhibit complex flow profiles or regions of static fluid. |
| T691 |
2755-2896 |
Sentence |
denotes |
For example, groundwater systems (e.g., aquifers), rivers, and lakes have been reported to have complex flow profiles (Ji, 2017; Zhang et al. |
| T692 |
2897-2903 |
Sentence |
denotes |
1996). |
| T693 |
2904-3023 |
Sentence |
denotes |
Thus, the sampling approach should be considered when examining droplet formats for food and water safety applications. |
| T694 |
3024-3264 |
Sentence |
denotes |
In addition to a consideration of system mixing, one should also consider the potential measurement pitfalls when analyzing samples that contain dilute levels of highly infectious pathogens, such as the potential for false-negative results. |
| T695 |
3265-3349 |
Sentence |
denotes |
Flow formats involve the detection of target species in the presence of flow fields. |
| T696 |
3350-3477 |
Sentence |
denotes |
Flow formats include continuously-stirred systems (e.g., continuously-stirred tank bioreactors), flow cells, and microfluidics. |
| T697 |
3478-3730 |
Sentence |
denotes |
Flow formats have the advantage of exposing the biosensor to target-containing samples in a controlled and repeatable fashion and the benefit of driving exposure of the functionalized biosensor to target species via convective mass transfer mechanisms. |
| T698 |
3731-3808 |
Sentence |
denotes |
Flow formatsare also typically compatible with large sample volumes (liters). |
| T699 |
3809-3925 |
Sentence |
denotes |
Flow cells are typically fabricated via milling and extrusion processes using materials such as Teflon or Plexiglas. |
| T700 |
3926-4047 |
Sentence |
denotes |
They have the advantage of accommodating a variety of biosensor form factors, such as rigid three-dimensional biosensors. |
| T701 |
4048-4137 |
Sentence |
denotes |
In addition to flow cells, flow formats are commonly achieved using microfluidic devices. |
| T702 |
4138-4317 |
Sentence |
denotes |
While microfluidic devices are typically used with biosensors that exhibit thin two-dimensional form factors, such as planar electrodes, they offer various measurement advantages. |
| T703 |
4318-4574 |
Sentence |
denotes |
Unlike flow cells, which are typically fabricated from machinable polymers, microfluidics are typically fabricated using polydimethylsiloxane (PDMS) and polymethyl methacrylate (PMMA) given their low cost and compatibility with microfabrication approaches. |
| T704 |
4575-4768 |
Sentence |
denotes |
One advantage of microfluidic devices is their ability to perform integrated sample preparation steps, which eliminates the need for additional steps in the sample-to-result process (Sin et al. |
| T705 |
4769-4775 |
Sentence |
denotes |
2014). |
| T706 |
4776-4956 |
Sentence |
denotes |
For example, microfluidic formats for pathogen detection using electrochemical biosensors have demonstrated fluid pumping, valving, and mixing of small sample volumes (Rivet et al. |
| T707 |
4957-4963 |
Sentence |
denotes |
2011). |
| T708 |
4964-5095 |
Sentence |
denotes |
An example of a microfluidic format created by Dastider et al. for detection of S. typhimurium is shown in Fig. 4a (Dastider et al. |
| T709 |
5096-5102 |
Sentence |
denotes |
2015). |
| T710 |
5103-5233 |
Sentence |
denotes |
Detection in the presence of flow fields requires high stability of immobilized biorecognition elements (Bard and Faulkner, 2000). |
| T711 |
5234-5433 |
Sentence |
denotes |
The effect of flow characteristics on biosensor collection rates is an important consideration, especially when considering micro- and nano-scale transducers with microfluidic formats (Squires et al. |
| T712 |
5434-5440 |
Sentence |
denotes |
2008). |
| T713 |
5441-5614 |
Sentence |
denotes |
For example, emerging nanostructured electrodes, such as functionalized nanoporous membranes, have been shown to achieve high stability in microfluidic devices (Joung et al. |
| T714 |
5615-5631 |
Sentence |
denotes |
2013; Tan et al. |
| T715 |
5632-5638 |
Sentence |
denotes |
2011). |
| T716 |
5639-5843 |
Sentence |
denotes |
A detailed discussion on the relationship between device dimensions, flow characteristics, achievable target collection rates, and equilibrium measurement times has been provided elsewhere (Squires et al. |
| T717 |
5844-5850 |
Sentence |
denotes |
2008). |
| T718 |
5851-6136 |
Sentence |
denotes |
It is paramount for interpreting biosensor response that users understand the interplay between mass transport of target molecules (both diffusive and convective mechanisms) and reaction at the biosensor surface (i.e., binding of target species to immobilized biorecognition elements). |
| T719 |
6137-6316 |
Sentence |
denotes |
Such fundamental understanding can also be employed in biosensor and experiment design to create improved assay outcomes, such as reducing TTR or improving measurement confidence. |
| T720 |
6317-6655 |
Sentence |
denotes |
While the presence of pathogens on the surfaces of objects can be analyzed using droplet- and flow-based sample handling formats using material transfer processes, such as swabbing, in situ pathogen detection on the object surfaces is a vital measurement capability for medical diagnostic, infection control, and food safety applications. |
| T721 |
6656-6781 |
Sentence |
denotes |
Surface-based measurement formats typically require biosensors with flexible or conforming (i.e., form-fitting) form factors. |
| T722 |
6782-6929 |
Sentence |
denotes |
For example, Mannoor et al. detected the presence of pathogenic species directly on teeth using a flexible graphene-based biosensor (Mannoor et al. |
| T723 |
6930-6936 |
Sentence |
denotes |
2012). |
| T724 |
6937-7044 |
Sentence |
denotes |
Further discussion of surface-based pathogen detection applications are provided in the following sections. |
| T725 |
7045-7128 |
Sentence |
denotes |
The sample handling format often provides insight into the biosensor's reusability. |
| T726 |
7129-7247 |
Sentence |
denotes |
Biosensors within the aforementioned measurement formats can be broadly classified as single- or multi-use biosensors. |
| T727 |
7248-7430 |
Sentence |
denotes |
Single-use biosensors are unable to monitor the analyte concentration continuously or upon regeneration, while multiple-use biosensors can be repeatedly recalibrated (Thévenot et al. |
| T728 |
7431-7437 |
Sentence |
denotes |
2001). |
| T729 |
7438-7683 |
Sentence |
denotes |
For example, droplet-based low-cost, disposable biosensors for water safety are typically single-use, while biosensors for process monitoring applications can be recalibrated to characterize multiple samples and facilitate continuous monitoring. |
| T730 |
7684-7970 |
Sentence |
denotes |
The ability to regenerate biosensor surfaces following pathogen detection (i.e., remove selectively-bound pathogens) is a significant technical barrier limiting progress in multiple-use biosensors, and industrial applications thereof, and is discussed further in the following sections. |
