Field-Portable Microplastic Sensing in Aqueous Environments: A Perspective on Emerging Techniques.

Microplastics (MPs) have been found in aqueous environments ranging from rural ponds and lakes to the deep ocean. Despite the ubiquity of MPs, our ability to characterize MPs in the environment is limited by the lack of technologies for rapidly and accurately identifying and quantifying MPs. Although standards exist for MP sample collection and preparation, methods of MP analysis vary considerably and produce data with a broad range of data content and quality. The need for extensive analysis-specific sample preparation in current technology approaches has hindered the emergence of a single technique which can operate on aqueous samples in the field, rather than on dried laboratory preparations. In this perspective, we consider MP measurement technologies with a focus on both their eventual field-deployability and their respective data products (e.g., MP particle count, size, and/or polymer type). We present preliminary demonstrations of several prospective MP measurement techniques, with an eye towards developing a solution or solutions that can transition from the laboratory to the field. Specifically, experimental results are presented from multiple prototype systems that measure various physical properties of MPs: pyrolysis-differential mobility spectroscopy, short-wave infrared imaging, aqueous Nile Red labeling and counting, acoustophoresis, ultrasound, impedance spectroscopy, and dielectrophoresis.

Quantum cascade laser-based reflectance spectroscopy: a robust approach for the classification of plastic type.

The identification of plastic type is important for environmental applications ranging from recycling to understanding the fate of plastics in marine, atmospheric, and terrestrial environments. Infrared reflectance spectroscopy is a powerful approach for plastics identification, requiring only optical access to a sample. The use of visible and near-infrared wavelengths for plastics identification are limiting as dark colored plastics absorb at these wavelengths, producing no reflectance spectra. The use of mid-infrared wavelengths instead enables dark plastics to be identified. Here we demonstrate the capability to utilize a pulsed, widely-tunable (5.59 - 7.41 µm) mid-infrared quantum cascade laser, as the source for reflectance spectroscopy, for the rapid and robust identification of plastics. Through the application of linear discriminant analysis to the resulting spectral data set, we demonstrate that we can correctly classify five plastic types: polyethylene terephthalate (PET), high density polyethylene (HDPE), low density polyethylene (LDPE), polypropylene (PP), and polystyrene (PS), with a 97% accuracy rate.

Rapid Identification of Marine Plastic Debris via Spectroscopic Techniques and Machine Learning Classifiers.

To advance our understanding of the environmental fate and transport of macro- and micro-plastic debris, robust and reproducible methods, technologies, and analytical approaches are necessary for in situ plastic-type identification and characterization. This investigation compares four spectroscopic techniques: attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), near-infrared (NIR) reflectance spectroscopy, laser-induced breakdown spectroscopy (LIBS), and X-ray fluorescence (XRF) spectroscopy, coupled to seven classification methods, including machine learning classifiers, to determine accuracy for identifying type of both consumer plastics and marine plastic debris (MPD). With machine learning classifiers, consumer plastic types were identified with 99, 91, 97, and 70% success rates for ATR-FTIR, NIR reflectance spectroscopy, LIBS, and XRF, respectively. The classification of MPD had similar or lower success rates, likely arising from alterations to the plastic from environmental weathering processes with success rates of 99, 81, 76, and 66% for ATR-FTIR, NIR reflectance spectroscopy, LIBS, and XRF, respectively. Success rates indicate that ATR-FTIR, NIR reflectance spectroscopy, and LIBS coupled with machine learning classifiers can be used to identify both consumer and environmental plastic samples.

The M/V X-Press Pearl Nurdle Spill: Contamination of Burnt Plastic and Unburnt Nurdles along Sri Lanka's Beaches.

In May 2021, the M/V X-Press Pearl cargo ship caught fire 18 km off the west coast of Sri Lanka and spilled ∼1680 tons of spherical pieces of plastic or "nurdles" (∼5 mm; white in color). Nurdles are the preproduction plastic used to manufacture a wide range of end products. Exposure to combustion, heat, and chemicals led to agglomeration, fragmentation, charring, and chemical modification of the plastic, creating an unprecedented complex spill of visibly burnt plastic and unburnt nurdles. These pieces span a continuum of colors, shapes, sizes, and densities with high variability that could impact cleanup efforts, alter transport in the ocean, and potentially affect wildlife. Visibly burnt plastic was 3-fold more chemically complex than visibly unburnt nurdles. This added chemical complexity included combustion-derived polycyclic aromatic hydrocarbons. A portion of the burnt material contained petroleum-derived biomarkers, indicating that it encountered some fossil-fuel products during the spill. The findings of this research highlight the added complexity caused by the fire and subsequent burning of plastic for cleanup operations, monitoring, and damage assessment and provides recommendations to further understand and combat the impacts of this and future spills.

Flow-Through Quantification of Microplastics Using Impedance Spectroscopy.

Understanding the sources, impacts, and fate of microplastics in the environment is critical for assessing the potential risks of these anthropogenic particles. However, our ability to quantify and identify microplastics in aquatic ecosystems is limited by the lack of rapid techniques that do not require visual sorting or preprocessing. Here, we demonstrate the use of impedance spectroscopy for high-throughput flow-through microplastic quantification, with the goal of rapid measurement of microplastic concentration and size. Impedance spectroscopy characterizes the electrical properties of individual particles directly in the flow of water, allowing for simultaneous sizing and material identification. To demonstrate the technique, spike and recovery experiments were conducted in tap water with 212-1000 µm polyethylene beads in six size ranges and a variety of similarly sized biological materials. Microplastics were reliably detected, sized, and differentiated from biological materials via their electrical properties at an average flow rate of 103 ± 8 mL/min. The recovery rate was ≥90% for microplastics in the 300-1000 µm size range, and the false positive rate for the misidentification of the biological material as plastic was 1%. Impedance spectroscopy allowed for the identification of microplastics directly in water without visual sorting or filtration, demonstrating its use for flow-through sensing.

Prostaglandin production in human coronary artery endothelial cells is modulated differentially by selective phospholipase A(2) inhibitors.

Atherosclerotic plaque formation is a dynamic process involving repeated injury and inflammation of the endothelium. We have demonstrated previously that thrombin and tryptase stimulation of human coronary artery endothelial cells (HCAEC) leads to increased phospholipase A(2) (PLA(2)) activity and generation of membrane phospholipid derived inflammatory metabolites, including eicosanoids and platelet activating factor. Thus, our hypothesis is that selective PLA(2) inhibitors have therapeutic potential as anti-inflammatory agents. Stimulation of confluent HCAEC monolayers with thrombin or tryptase resulted in a concentration and time-dependent increase in both prostaglandin E(2) (PGE(2)) and prostacyclin (PGI(2)) production. Pretreatment with PX-18 to inhibit secretory PLA(2) or BEL to inhibit calcium-independent PLA(2) prior to thrombin or tryptase stimulation resulted in a significant inhibition of both PGI(2) and PGE(2) release. However, pretreatment with methyl arachidonyl fluorophosphonate (MAFP), a widely used inhibitor of cytosolic PLA(2) isoforms, resulted in a significant potentiation of both thrombin and tryptase stimulated PGI(2) and PGE(2) release as a consequence of increased free arachidonic acid production. We conclude that the use of selective PLA(2) inhibitors may be of therapeutic benefit in the development and progression of atherosclerosis, however, the development of such an agent requires rigorous screening.

Phospholipase A2 inhibitors as potential anti-inflammatory agents.

Phospholipase A(2) (PLA(2))-catalyzed hydrolysis of membrane phospholipids results in the stoichiometric production of a free fatty acid, most importantly arachidonic acid, and a lysophospholipid. Both of these phospholipid metabolites serve as precursors for inflammatory mediators such as eicosanoids or platelet-activating factor (PAF). Since it was initially discovered that non-steroidal anti-inflammatory drugs inhibit prostaglandin synthesis, a vast amount of drug development has been performed to selectively inhibit the production of the inflammatory metabolites of arachidonic acid while preserving their protective role. This research has culminated in the development of selective cyclooxygenase-2 (COX-2) inhibitors that act on the inducible, inflammatory COX enzyme, but do not affect the constitutive prostaglandin synthesis in cells that is mediated via COX-1. The development of PLA(2) inhibitors as potential anti-inflammatory agents has also been extensively pursued since the release of arachidonic acid from membrane phospholipids by PLA(3) is one of the rate-limiting factors for eicosanoid production. In addition to the production of eicosanoids, PLA(2)-catalyzed membrane phospholipid hydrolysis is also the initiating step in the generation of PAF, a potent inflammatory agent. Thus, inhibition of PLA(2) activity should, in theory, be a more effective anti-inflammatory approach. However, developing an inhibitor that would be selective for the production of inflammatory metabolites and not inhibit the beneficial properties of PLA(2) has so far proved to be elusive. This review will focus on agents used currently to inhibit PLA(2) activity and will explore their possible therapeutic use.

Special considerations of antibiotic prescription in the geriatric population.

Infectious diseases pose a major challenge in the elderly for two reasons: on the one hand the susceptibility to infection increases with age and when infections occur they often present atypically-on the other hand diagnostic uncertainty is much more pronounced in the geriatric population. Reconciling the opposing aspects of optimizing patient outcomes while avoiding antibiotic overuse requires significant expertise that can be provided by an infectious diseases consultant. In addition, geriatric facilities are reservoirs for multidrug-resistant organisms and other nosocomial pathogens, and infectious diseases consultants also play a vital role in assuring appropriate infection control measures. In this review we outline the challenges of diagnosis and management of infectious diseases in the elderly, and discuss the importance of appropriate antibiotic use in the elderly in order to demonstrate the value of the infectious diseases consultant in this special setting.

Effect of bending direction on the mechanical behaviour of 3.5 mm String-of-Pearls and Limited Contact Dynamic Compression Plate constructs.

OBJECTIVE: To compare the bending properties of String-of-Pearls® (SOP) and Limited Contact Dynamic Compression Plate® (LC-DCP) constructs in orthogonal bending directions. METHODS: 3.5 mm SOP and LC-DCP plates were fixed to a bone model simulating a comminuted tibial fracture. Specimens were non-destructively tested in both mediolateral and craniocaudal bending for 10 cycles. Bending stiffness and total angular deformation were compared using parametric analyses (p <0.05). RESULTS: For both constructs, stiffness was significantly less when bending moments were applied against the thickness of the plates (mediolateral bending) than against the width (craniocaudal bending). When compared to the mediolateral plane, bending constructs in the craniocaudal plane resulted in a 49% (SOP group) and 370% (LC-DCP group) increase in stiffness (p <0.001). Mediolateral bending stiffness was significantly greater in the SOP than the LC-DCP constructs. Conversely, in craniocaudal bending, SOP constructs stiffness was significantly less than that of the LC-DCP constructs. The differences between the two constructs in total angular deformation had an identical pattern of significance. CLINICAL SIGNIFICANCE: This study found that SOP showed less variability between the orthogonal bending directions than LC-DCP in a comminuted fracture model, and also described the bi-planar bending behaviour of both constructs. Although not exhibiting identical bending properties in both planes, SOP constructs had a more homogenous bending behaviour in orthogonal loading directions. The difference between the SOP with a circular cross sectional shape compared to the rectangular shape of standard plates is probably responsible for this difference.

Mapping dose distributions.

Clinical dose calculations are often performed by scaling distances from a dose distribution measured in one medium to calculate the dose in another. These perturbation calculations have the mathematical form of a mapping. In this paper we identify five conditions required for particle transport to reduce to this form and develop a new mapping for electrons which approximately satisfies these conditions. This continuous scattering mapping is based on two parameters, the scattering power of the medium which determines the shape of the scaling paths, and the stopping power of the medium which determines where the energy is deposited along these paths. Pencil beam dose distributions are calculated with EGS4 in one medium and mapped to other media. The resultant distributions are compared with EGS4 calculations done directly in the second medium. The accuracy of the mapping algorithm is shown to be superior to both linear density scaling and the MDAH electron pencil beam algorithm [Kenneth R. Hogstrom, Michael D. Mills, and Peter R. Almond, "Electron beam dose calculations," Phys. Med. Biol. 26, 445-459 (1981)] for pencil beams in homogeneous media and inhomogeneous phantoms (both slab and nonslab geometries) for a variety of materials of clinical interest.

Gluten-induced nitric oxide and pro-inflammatory cytokine release by cultured coeliac small intestinal biopsies.

OBJECTIVES: To determine whether there was increased nitric oxide (NO) production from coeliac small intestinal biopsies cultured in vitro with gluten and whether the inhibition of NO production could prevent gluten-induced enterotoxicity. The relationship between NO production with the pro-inflammatory cytokines interferon-gamma (IFN-gamma), tumour necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) was evaluated. DESIGN: Small intestinal biopsies from ten patients with treated coeliac disease and six controls were studied. METHODS: Small intestinal biopsies were taken from each patient and set up in culture with Frazer's fraction III (FFIII), a peptic/tryptic digest of gluten, FFIII plus L-NMMA and L-NMMA alone, culture medium alone and ovalbumin which served as a control protein. The biopsies were cultured for 20 h at 37 degrees C. The supernatants were then collected and analysed for nitrite using the Greiss reaction; cytokine levels were determined using ELISA kits. Enterocyte height was determined by microscopy using a calibrated eyepiece graticule and cryostat sections of the cultured biopsies. RESULTS: Coeliac biopsies cultured with FFIII produced significantly greater nitrite compared to culture medium alone (P< 0.05) and this could be blocked with L-NMMA (P< 0.01). A reduction in enterocyte height was seen in coeliac biopsies cultured with FFIII compared to culture medium alone (P < 0.01) and this was ameliorated but not completely blocked when FFIII was cultured with L-NMMA. These changes were not seen in the controls. There was a significant reduction in IL-1beta levels in the supernatant of coeliac biopsies cultured with FFIII compared to culture medium alone (P< 0.05), but when cultured with FFIII and L-NMMA there was a significant increase in IL-1beta levels (P< 0.05). An increase in IFN-gamma levels was also seen when coeliac biopsies were cultured with FFIII and L-NMMA (P< 0.05). This pattern was not seen with TNF-alpha. CONCLUSIONS: Increased levels of NO can be found when coeliac biopsies are cultured with gluten in an in vitro small intestinal culture system, and NO may play a role in the observed enterotoxicity as the inhibition of NO production ameliorates the enterocyte damage. The results suggest that NO is involved in the regulation of pro-inflammatory cytokines, particularly IL-1beta. This is likely to be one of many pathways leading to the observed mucosal pathology in coeliac disease and demonstrates the close interactions between them.

The detection and localization of inducible nitric oxide synthase production in the small intestine of patients with coeliac disease.

OBJECTIVES: To investigate whether there are increased numbers of inducible nitric oxide synthase (iNOS) containing cells in the small intestine of patients with coeliac disease and the localization of nitric oxide synthase production. DESIGN: Small intestinal biopsy specimens from patients with coeliac disease (11 untreated, 10 treated) and nine disease controls were studied. METHODS: Histochemical staining of sections for NADPH-diaphorase activity was performed, which gives an indication of NOS activity. iNOS protein was detected with immunohistochemistry and iNOS mRNA expression was detected using in situ hybridization with an oligonucleotide probe cocktail for iNOS. Cell phenotype was detected using monoclonal antibodies to CD3 (T-lymphocytes) and CD45 (total inflammatory cell infiltrate). RESULTS: There was significantly greater NADPH diaphorase staining in the lamina propria of patients with untreated coeliac disease (P < 0.005). The same pattern was found for immunohistochemical and in situ hybridization methods of staining for iNOS in each of the patient groups (P < 0.005) but no epithelial staining was seen with any method. The pattern of iNOS staining in the lamina propria appeared in a similar distribution to that of the inflammatory cell infiltrate. At least 80% of the significantly increased total inflammatory cell infiltrate (CD45) in the lamina propria of patients with untreated coeliac disease was lymphocytic (CD3) whilst the iNOS staining cells made up less than 15% of the total inflammatory cell infiltrate. CONCLUSIONS: There is a significant increase in the number of NOS staining cells of the inducible isoform in the lamina propria of patients with untreated coeliac disease. The lamina propria and not the epithelium is the site of iNOS production in coeliac disease. It appears that inflammatory cells other than T-lymphocytes are likely to be the cellular sources of iNOS production within the lamina propria. This is the first study to demonstrate increased numbers of iNOS producing cells in the small intestine of patients with untreated coeliac disease and suggests a role for nitric oxide in the pathogenesis of the histological changes seen in coeliac disease although it may be a non-specific inflammatory response to immune activation by gluten in susceptible individuals.

Effects of an energy and micronutrient supplement on growth and activity, correcting for non-supplemental sources of energy input in undernourished children in Indonesia.

OBJECTIVES: This paper investigates simultaneously the growth and activity of children that received an early energy and micronutrient supplement, adjusting for all non-supplemental energy intakes. Any additional change in growth and activity after this adjustment was then compared across supplements at three points felt to be representative of the study. DESIGN: Two cohorts of children were randomly assigned to three treatments: E = 1171 kJ + 12 mg iron; M = 209 kJ + 12 mg iron; S = 104 kJ. Supplementation was given for 12 months. SETTING: The sites were six tea plantations in Pangalengan, West Java. SUBJECTS: A 12-month-old (n = 53) and an 18-month-old (n = 83) cohort were recruited from day-care-centers. Twenty children that received S belonged to the 12- and 18-month-old cohorts. Inclusion criteria were: no chronic disease; length-for-age < or = -1 standard deviation (s.d.) and weight-for-length between -1 and -2 s.d. of the median of the reference of the World Health Organization. METHODS: Length was measured with a portable measuring board; a Detecto scale with an accuracy of 0.1 kg was used for the measurement of body weight. Arm and head circumferences were measured using similar fiberglass tapes. Motor activity was assessed through continuous 4 h observations at home and at day care centers. Anthropometry and activity were measured every two months over 12 months. RESULTS: After correcting for non-supplemental sources of energy intake, the effects of the supplement on weight and activity were observed at 2 months; effects on length and activity were observed at 6 months; and effects on weight alone were observed at 12 months.

Effects of an energy and micronutrient supplement on anthropometry in undernourished children in Indonesia.

OBJECTIVES: This paper reports the effects of early supplementary feeding on body weight, length, head circumference and arm circumference among the children in the Pangalengan study. DESIGN: Two cohorts of children were randomly assigned to three treatments: E = 1171 kJ + 12 mg iron; M = 209 kJ + 12 mg iron; S = 104 kJ. Supplementation was given for 12 months. SETTING: The sites were six tea plantations in Pangalengan, West Java. SUBJECTS: A 12-month-old (n = 53) and an 18-month-old (n = 83) cohort were recruited from day-care centers. Twenty children that received S belonged to the 12- and 18-month cohorts. Inclusion criteria were: no chronic disease; length-for-age < or = -1 standard deviation (s.d.) and weight-for-length between -1 and -2 s.d. of the median of the reference of the World Health Organization. METHODS: Length was measured with a portable measuring board; a Detecto scale with an accuracy of 0.1 kg was used for the measurement of body weight. Arm and head circumferences were measured using similar fiberglass tapes. RESULTS: Body weight showed effects on both cohorts at 2, 8 and 12 months; head circumference showed effects at 4 months in the 12-month-old cohort and at 10 months among the females of the 18-month-old cohort; and arm circumference showed effects across cohorts at 2, 8 and 12 months. In general the benefits are clearer for females and for the 12-month-old cohort.

Nutritional intake of an undernourished infant population receiving an energy and micronutrient supplement in Indonesia.

OBJECTIVES: This paper reports the dietary intake (home, day care centers, supplement and breast milk) of the children in the clinical trial in Pangalengan. DESIGN: Two cohorts of children were randomly assigned to three treatments: E = 1171 kJ + 12 mg iron; M = 209 kJ + 12 mg iron; S = 104 kJ. Supplementation was given for 12 months. SETTING: The sites were six tea plantations in Pangalengan, West Java. SUBJECTS: A 12-month-old (n = 53) and an 18-month-old (n = 83) cohort were recruited from day-care-centers. Twenty children who received S belong to the 12- and 18-month-old cohorts. Inclusion criteria were: no chronic disease; length-for-age < or = -1 standard deviation (s.d.) and weight-for-length between -1 and -2 s.d. of the median of the reference of the World Health Organization. METHODS: E = 1171 kJ + 12 mg iron; M = 209 kJ + 12 mg iron; S = 104 kJ. Supplementation was given for 12 months. Evaluations of intake were made at baseline and every 2 months thereafter. RESULTS: For the 12-month-old cohort the mean increase in daily energy intake approximately 2931 kJ for E, approximately 1675 kJ for M, and approximately 837 kJ increase over the 6 months for the S group. For the 18-month-old cohort the changes were approximately 2512 kJ for E approximately 1675 for the M group and approximately 1047 for the S group.

Is it possible to predict the blood volume of a sick preterm infant?

OBJECTIVE: To investigate the relation between the measured intravascular blood volume (BV) and current methods of indirectly assessing BV status in sick preterm infants on the first day of life. METHODS: Thirty eight preterm infants of gestation 24-32 weeks (median 30) and weight 480-2060 g (median 1220) were studied. Red cell volume was measured by the fetal haemoglobin dilution method in six infants and by the biotin labelled autologous red cell dilution method in the remaining 32. Total BV was calculated by dividing red cell volume by packed cell volume. Indirect assessments of BV status using heart rate (HR), core-peripheral temperature difference, mean arterial pressure, base excess, and packed cell volume were recorded. RESULTS: The mean (SD) initial measured BV was 71 (12) ml/kg (range 53-105). The mean HR was 148 beats/min (range 130-180), which correlated positively (r = 0.39, p = 0.02) with BV (higher HR was associated with higher BV). The mean base excess was -3.19 mmol/l (range -18 to +6.2). The negative base excess correlated significantly positively (r = 0.41, p < 0.01) with BV (more acidotic babies tended to have higher BV). There was no significant correlation between core-peripheral temperature difference, mean arterial pressure, or packed cell volume and BV. Regression analysis showed that base excess and HR were significantly related to BV; base excess alone can predict variability in BV only to 17%, and base excess with HR can predict variability in BV to 29%. CONCLUSION: The conventional clinical and laboratory indices are poor predictors of measured blood volume.

In situ hybridization.

In situhybridization permits specific identification of genes and gene expression without removing the target sequence from its topographical surroundings. The technique was described simultaneously in 1960 by two groups (1,2). It depends on the hybridization of a labeled nucleic acid probe to a complementary sequence of tissue mRNA or DNA.

Effects of qualities of early institutional care on cognitive attainment. E.R.A. Study Team. English and Romanian Adoptees.

The adoption of children reared in poor quality Romanian institutions provided a "natural experiment" to determine whether psychological privation is the cause of later deficits. Low IQ at six years was strongly related to the duration of institutional care, with malnutrition having a weaker effect. After taking both into account, there was an additional effect of a particularly marked lack of individualized care.