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The use of an alumina-coated ZnSe internal reflection element (IRE) to detect spores by attenuated total reflection infrared spectroscopy (FTIR-ATR) was investigated. Two methods for coating the IRE with alumina are described. It is shown that the adsorption proceeds through an interaction of the carboxylate groups on Bacillus globigii (BG) and pos...
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... for deposition on the alumina/PE film corresponds to 3.25 3 10 8 spores/cm 2 . Assuming single-layer coverage of spores, this value in the number of spores per cm 2 area of the IRE would correspond to a tightly packed layer on the alumina. This was confirmed by obtaining AFM images of the alumina/ PE coated IRE after deposition of the spores (see Fig. 4), which show a uniform and highly packed layer of spores on the ...
Citations
... Fourier-transform infrared (FTIR) spectroscopy, coupled with attenuated total reflection (ATR), can be used to probe trace amounts of spores [9] or other particles on solid surfaces [10], or remotely by imaging [11,12]. Active methods for powders detection, in which the investigated sample is artificially illuminated rather than using ambient light, were also applied in various spectral regions, such as THz [13,14], but more commonly in lower wavelengths. ...
Identification of particulate matter and liquid spills contaminations is essential for many applications, such as forensics, agriculture, security, and environmental protection. For example, toxic industrial compounds deposition in the form of aerosols, or other residual contaminations, pose a secondary, long-lasting health concern due to resuspension and secondary evaporation. This chapter explores several approaches for employing diffuse reflectance spectroscopy in the mid-IR and SWIR to identify particles and films of materials in field conditions. Since the behavior of thin films and particles is more complex compared to absorption spectroscopy of pure compounds, due to the interactions with background materials, the use of physical models combined with statistically-based algorithms for material classification, provides a reliable and practical solution and will be presented.
... Identifying dormant, highly resistant persister cells within a biofilm would be beneficial for improving clinical treatment strategies and diagnostics. [11] While numerous studies have identified the potential of FTIR to detect and characterize bacterial endospores (highly resistant, dormant intracellular structures present in spore-producing genera such as Bacillus and Clostridium), [43,[154][155][156][157][158][159][160][161][162][163][164][165] these bacteria are more commonly associated with food contamination than biofilm infection. [166] It remains to be seen whether FTIR spectroscopy can identify dormant persister cells that are an important mechanism for persistence in biofilm infections. ...
Bacterial biofilms play a role in a majority of chronic infections. Such infections are the result of bacterial colonization and matrix construction, which yield protective structures that are much more difficult to treat than planktonic (free-floating), acute infections. Because of the medical challenges that biofilm infections impose, technological advancements and innovation for diagnosis, characterization, and treatment are greatly needed. One technology which has been increasingly recognized for its potential in biofilm characterization is Fourier transform infrared (FTIR) spectroscopy. As such, the aim of this review is to discuss the state of FTIR research in its application to medical microbiology and to offer insight into its prospective adoption by healthcare providers.
... ATR is widely used to obtain the spectra of solids, liquids, semisolids and thin film, and it is particularly good for in situ sample measurements in the aqueous environment, because the small (1-10 microns) penetration depth of the evanescent wave reduces absorption of infrared radiation by water [10]. Therefore, researchers developed many approaches based on FTIR to study the proteins, microorganisms [11][12][13], and developed mathematical methods to distinguish the secondary structure of proteins [14][15][16][17][18] and different species of microorganisms [19]. ...
Undesired adsorption of proteins brings big troubles to marine structures. The settled proteins change the physical and chemical properties of the surfaces, which allow marine fouling organisms to settle down on the structures. Therefore, to understand the adsorption mechanism of proteins is very helpful to find an environment-friendly solution against biofouling. Many approaches have been developed to study protein adsorption, but most of them are insufficient to give the chemical interaction information between proteins and surfaces. Fourier transform infrared spectroscopy with attenuated total reflection (FTIR-ATR)is an efficient, fast and non-destructive method for in situ surface measurement, which greatly minimizes the interference of water to infrared spectra, because of the very small depth of penetration of the evanescent wave. In this paper, an in situ FTIR-ATR technology was used to investigate the adsorption process of trypsin on a bare ZnSe surface and on a TiO 2 coated ZnSe surface, and the effect of calcium cation strength and ultraviolet light irradiation on the secondary structure of trypsin were also evaluated. FTIR spectra of trypsin showed that Amide I band red shift and Amide II band blue shift in aqueous environment on both surfaces compared with the dry trypsin powder, and the addition of calcium cations further changed the Amide bands position, which indicated that the change of the secondary structure could be interfered by the environment. The hydrogen bond formation between water and trypsin, the interaction between surface and trypsin, the interaction between hydrated calcium cations and trypsin, are major factors to change the secondary structure of trypsin, and UV light irradiation also showed its influence for the secondary structure.
... Spectroscopy has been used for studying conformation of protein since past decades. FTIR is an ideal technology for rapid and non-destructive detection to biological samples, because it can give the information of biological samples in minutes, and does not require harmful reagent, kill the live cells, and break the chemical structures [19,20]. Limited by the sensitivity of IR instrument and the interference of water to protein absorption band, the early studies focused on dry powder and heavy water state [21,22]. ...
The secondary structural changes of bovine serum albumin (BSA) aqueous solutions with and without calcium cations were investigated by attenuated total reflection-Fourier transform infrared (ATR-FTIR) technology. The spectra of BSA solution and BSA dry powder were mainly reflected the formation of hydrogen bonds between water and BSA. Further investigation indicated that the concentrations of calcium cations in BSA aqueous solution also affected the secondary structural change of the protein. Amide I band was red shifted and amide II band was blue shifted in aqueous environment compared with the dry BSA powder, and the addition of calcium cations further changed the amide bands position, which led to the change of the secondary structure. The result was coinciding with the Raman spectroscopy.
... Many experiments had been designed to investigate the bacteria settlement process on the surface and the influence thereafter [8][9][10][11]. Scanning electron microscopy (SEM) had been used to provide information of surface morphology and properties of the EPS [8]. But it could not be used to monitor in situ settlement process in aqueous circumstance. ...
... But it could not be used to monitor in situ settlement process in aqueous circumstance. Atomic force microscopy (AFM) had been employed to study the strength of attachment Ulva spore [9][10][11]. Hydrodynamic methods had also been used to measure the adhesion strength of Ulva spores using a water jet apparatus [9]. ...
... Therefore, attenuated total reflection infrared (ATR-IR) spectroscopy was introduced in this study because there was limited penetration of IR radiation into the aqueous medium and it was also a nondestructive detection method which provided an in situ approach to monitor the bacteria settlement process on the surface in aqueous environment [12]. Previously, ATR-FTIR spectroscopy had been used in rapidly detecting Bacillus globigii spores [11], exploring microbes adsorbing metal ions in industrial wastewater [18,19], microbes adsorbing toxic ions and analyzing phosphate adsorption onto hematite [19]. In this paper, ATR-FTIR spectroscopy was applied to investigate the bio-reaction continuously during gram-positive Bacillus sp. and gram-negative Escherichia coli settlement on bare and Al 2 O 3 coated ZnSe surface, respectively. ...
Marine microorganism accumulated on the surface of ships or pipelines would accelerate fouling organisms, such as mussels and barnacles, adhered on the surface. It was significant to understand the bio-interaction between the microorganisms and the surface. Attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy was used to study the initial stages of marine microorganism adhering to surfaces, because it could probe the microorganism interaction to the surface regardless of the water interference. Bacillus sp. and Escherichia coli were selected to study the initial attachment on different surfaces, because they were typical fouling microorganisms and showed opposite Gram stain results. The assays were conducted respectively in dried and settled bacteria on two different surfaces (ZnSe, Al2O3 coated on ZnSe). IR spectra of settled bacteria showed amide I band red shift and amide II band blue shift in aqueous environment on both surfaces compared with the dry bacteria. The reasons of amide bands shift were investigated and it was discovered that the hydrogen bond between the water and the protein of the bacteria led to the protein secondary structure change. ATR-FTIR provided an approach to study the attachment process and showed dynamic changing process on the surface, and it could be an appropriate approach to study the interaction between proteins and chemicals.
A novel hybrid ceramic membrane incorporated with activated carbon (AC) was prepared and tested for two distinct end uses: a) phosphate removal from treated sewage effluent (TSE), and b) oil removal from saline water. The membrane was prepared by incorporating the cheap and high surface area powdered AC (10 wt.%) within an alumina (Al2O3) framework. AC incorporation enhances the adsorptive properties of the hybrid membranes and create a tortuous matrix of micro- & nano-channels, that eventually improved the overall porosity and total pore area of the membrane by 90% when compared with unmodified alumina membrane. Moreover, the modified ceramic membrane showed an increase of 71% in its hydrophilicity and an increase of 45% in its oleophobicity when compared to unmodified alumina membranes. Due to the enhancement in the porosity and hydrophilicity, the hybrid Al2O3/AC membrane showed a higher permeate flux in comparison with the unmodified membrane. The phosphate removal capacity of the modified membranes was evaluated by the treatment both of model solutions and real TSE. The novel Al2O3/AC membranes exhibited almost complete phosphate removal at 30 ppm phosphate concentration in the TSE while maintaining a high permeate flux of 18.9 L/m².h (LMH) compared to 2.8 LMH for the unmodified alumina membranes. The prepared Al2O3/AC membrane has demonstrated oil removal efficiency between 91% to 99% at emulsified oil concentrations ranging between 500 and 5000 parts per million (ppm). The modified membrane showed improved anti-fouling behavior during the filtration of oil and real TSE when compared with unmodified membrane. During the fouling resistance tests with emulsified oil, the Al2O3 membrane showed a noticeable normalized flux drop of about 60% after the sixth filtration cycle while only a slight decline in the normalized flux was found for Al2O3/AC membrane. The results of this work showed that the novel Al2O3/AC membrane can be used for the efficient removal of phosphate residue from TSE, and pretreatment of oil-containing wastewater.
We describe the characterization and application of quercetin pentaphosphate (QPP), a new fluorimetric substrate for the detection of alkaline phosphatase (ALP) activity. QPP exhibits major absorbance peaks at 260/410 nm and a strong fluorescence at λex/λem = 425/510 nm at alkaline pH. The product of enzymatic reaction between QPP and ALP has a strong absorbance peak at 324 nm with no fluorescence at the investigated wavelengths. The product generated from the enzymatic reaction was found to be proportional to ALP activity, and the ALP activity was monitored by the absorbance difference at 310 nm and 410 nm. The change in absorbance was found to be proportional to the ALP concentration with a linear detection range and a limit of detection of 0.01–16 U L−1 and 0.766 U L−1, respectively. The enzyme activity was also monitored by evaluating the change in fluorescence emission at 530 nm with a linear range of 0.01–8 U L−1 and a detection limit of 0.062 U L−1. Further, the validity of the new substrate for ALP in conjugated form was tested using Bacillus globigii spores as the model sample. A detection limit of 5998 spores per mL was obtained using QPP as the substrate. Unlike the parent compound, QPP substrate exhibits stability in solution for over three and half months and was stable under storage for over 12 months. The results obtained demonstrate the effectiveness of QPP for ALP and compare well with other fluorescent substrates, such as Fluorescein, Alexa Fluor and Cy5.
Mid-infrared (mid-IR) spectroscopy (4000–400 cm−1) has great potential for determining biochemical properties of microbes that are important to food quality and safety. For example, rapid and precise measurements of pathogenic and spoilage microorganisms present in food are possible, thanks to recent advances in detector technology and multivariate analysis. With mid-IR spectrometry it is possible to determine compositional properties of bacterial cell membranes, providing useful information about the genotype as well as phenotypical characteristics. In general, the most significant spectral regions for evaluation are Amide I (∼1650 cm−1), Amide II (∼1540 cm−1), polysaccharide (1200–900 cm−1), nucleic acid (∼1240 and ∼1080 cm−1), and certain lipid features, such as ω-cyclic fatty acids (∼2929 cm−1). Much research has been conducted to discriminate and quantify the specific microorganisms using this technique since the 1990s. In this chapter, we review recent work focusing on standardizing chemometric-processing steps, investigations of bacterial biofilms, spore characterization, microbial injury, and bacterial growth. Advantages and disadvantages of the application of IR spectral techniques for microbiological research are also presented.
Keywords:
infrared spectroscopy;
multivariate analysis;
spoilage microorganism;
pathogenic microorganism;
injury;
spore;
bacterial biofilm
An approach that integrates an electric field with an attenuated total reflection Fourier transform infrared spectroscopy (FTIR-ATR) flow through cell was used to detect spores in aqueous environments. A "proof of concept" in terms of the principle features of the method is described. It is shown that under an electric field, the negatively charged spores migrate and are concentrated on the surface of a ZnSe internal reflection element (IRE). No coating on the IRE is required, and a maximum amount adsorbed was obtained within the time needed to record the first spectrum. The amount adsorbed depends on both the pH and the ionic strength. Lowering the pH decreases the charge density and reduces the lateral-lateral repulsion force, leading to a higher packing density on the IRE. Reversal of the field does not overcome the strong attraction between the spores and the IRE. However, repeated measurements can be performed as the spores are completely and rapidly removed from the IRE by simply adding the next sample. The intensity of the infrared bands is due to mass loading of the spores on the IRE and setting a minimum value of 1 x 10(-3) absorbance; this requires a total of approximately 4 x 10(6) spores/cm(2). The theoretical detection limit in terms of spore concentration for our cell cavity height of 1.5 mm is approximately 10 ppm or 2.5 x 10(7) spores/cm(3).
Previous work using infrared spectroscopy has shown potential for rapid discrimination between bacteria in either their sporulated or vegetative states, as well as between bacteria and other common interferents. For species within one physiological state, however, distinction is far more challenging, and requires chemometrics. In the current study, we have narrowed the field of study by eliminating the confounding issues of vegetative cells as well as growth media and focused on using IR spectra to distinguish only between different species all in the sporulated state. Using principal component analysis (PCA) and a classification method based upon similarity measurements, we demonstrate a successful identification rate to the species level of 85% for Bacillus spores grown and sporulated in a glucose broth medium.
