Intelligent polarization-sensitive holographic flow-cytometer: Towards specificity in classifying natural and microplastic fibers.

Micron size fiber fragments (MFFs), both natural and synthetic, are ubiquitous in our life, especially in textile clothes, being necessary in modern society. In the Earth's aquatic ecosystem, microplastic fibers account for ~91% of microplastic pollution, thus deserving notable attention as one of the most alarming ecological problems. Accurate automatic identification of MFFs discharges in specific upstream locations is highly demanded. Computational microscopy based on Digital Holography (DH) and machine learning has been demonstrated to identify microplastics in respect to microalgae. However, DH is a non-specific optical tool, meaning it cannot distinguish different types of plastic materials. On the other hand, materials-specific assessments are pivotal to establish the environmental impact of different textile products and production processes. Spectroscopic assays can be employed to identify microplastics for their intrinsic specificity, although they are generally low-throughput and require large concentrations to enable effective measurements. Conversely, MFFs are usually finely dispersed within a water sample. Here we rely on a polarization-resolved holographic flow cytometer in a Lab-on-Chip (LoC) platform for analysing MFFs. We demonstrate that two important objectives can be achieved, i.e. adding material specificity through polarization analysis while operating in a microfluidic stream modality. Through a machine learning numerical pipeline, natural fibers (i.e. cotton and wool) can be clearly separated from synthetic microfilaments, namely PA6, PA6.6, PET, PP. Moreover, the proposed system can accurately distinguish between different polymers under investigation, thus fulfilling the specificity goal. We extract and select different features from amplitude, phase and birefringence maps retrieved from the digital holograms. These are shown to typify MFFs without the need for sample pre-treatment or large concentrations. The simplicity of the DH method for identifying MFFs in LoC-based flow cytometers could promote the use of polarization resolved field-portable analysis systems suitable for studying pollution caused by washing processes of synthetic textiles.

Contribution of microplastic particles to the spread of resistances and pathogenic bacteria in treated wastewaters.

Microplastic Particles (MPs) are ubiquitous pollutants widely found in aquatic ecosystems. Although MPs are mostly retained in wastewater treatment plants (WWTPs), a high number of MPs reaches the open waters potentially contributing to the spread of pathogenic bacteria and antibiotic resistance genes in the environment. Nowadays, a limited number of studies have focused on the role of MPs as carriers of potentially pathogenic and antibiotic resistant bacteria in WWTPs. Thus, an investigation on the community composition (by 16S rRNA gene amplicon sequencing) and the abundance of antibiotic and metal resistance genes (by qPCR) of the biofilm on MPs (the plastisphere) and of planktonic bacteria in treated (pre- and post-disinfection) wastewaters was performed. MPs resulted to be very similar in terms of type, color, size, and chemical composition, before and after the disinfection. The bacterial community on MPs differed from the planktonic community in terms of richness, composition, and structure of the community network. Potentially pathogenic bacteria generally showed higher abundances in treated wastewater than in the biofilm on MPs. Furthermore, among the tested resistance genes, only sul2 (a common resistance gene against sulfonamides) resulted to be more abundant in the plastisphere than in the planktonic bacterial community. Our results suggest that the wastewater plastisphere could promote the spread of pathogenic bacteria and resistance genes in aquatic environment although with a relatively lower contribution than the wastewater planktonic bacterial community.

Preparation and analysis of standards containing microfilaments/microplastic with fibre shape.

Synthetic clothing represents a primary source of environmental pollution because of shedding of microfilaments during laundry washing or in textile processes. Although many approaches can be used for the evaluation of microplastic, there are no precise guideline to follow for the analysis labs. Here, an accurate method for the preparation of microfilaments standard suspensions to facilitate lab tests and the monitoring of microplastic in different matrices was developed. Different standard suspensions were prepared by using five different synthetic threads consisting of a different number of filaments cut with a predetermined length of 0.2 mm suspended in three different volumes of water. The suspensions were filtered and the microfilaments were counted. The number of microfilaments for each polymer solution were statistically elaborated with a logit model and the results showed that the probability of detecting them is higher than 95% when the concentration of microfilaments/L is lower than 200. Moreover, a relationship between the theoretical microfilaments contained in the samples and the detection probability of the single microfilament, for each suspension volume was highlighted.

Assessment of microplastics release from polyester fabrics: The impact of different washing conditions.

Synthetic fibers account for approximately 60% of the total global fiber production, and polyester (PET) and polyamide (PA) dominate. Synthetic fabrics are now widely used in clothing, upholstery, carpets and other such materials. Textiles based on these materials have the potential to release microplastics (<5 mm in size) into the environment during production and cleaning actions. These particles are released in sewage effluents, as washing machine filters and wastewater treatment plants are not specifically designed to retain them and represent an environmental pollution that continuously increases the scientific and societal concern about their effects on marine biota and ecosystems. This study was focused on the determination of the amount of microfibers release from 100% polyester fabrics, in different washing conditions (programs and temperatures), comparing the use of detergent alone vs detergent with a stain remover. Microplastics released were characterized and quantified with gravimetric analysis, different microscopic, spectroscopic and thermal techniques. Tests were carried out in replicates to assess the data reproducibility and to show statistical differences between washing conditions.

Influence of process parameters on microcapsule formation from chitosan-Type B gelatin complex coacervates.

A series of chitosan/gelatin based microcapsules containing n-hexadecane was synthesized through complex phase coacervation from chitosan (CH) and type-B gelatin (GB), and crosslinked by glutaraldehyde (GTA). This research was conducted to clarify the influence of different parameters on the encapsulation process, i.e., the emulsion formation and the shell formation, using zeta potential and surface tension measurements, attenuated total reflectance (ATR), and thermal analysis such as differential scanning calorimetry (DSC). The optimal values of biopolymer ratios (TBP), crosslinker amount, emulsion time and feeding weight ratio of core/shell polymer (RCS) were identified. The stability of the emulsion was depended on the surface activity and TBP ratio, which also affected the droplet size distribution and the thickness of the shell. Furthermore, core content, encapsulation efficiency and thermal properties of the microcapsules were related to TBP and RCS; with the lowest RCS giving the best microcapsules features.

Evaluation of microplastic release caused by textile washing processes of synthetic fabrics.

A new and more alarming source of marine contamination has been recently identified in micro and nanosized plastic fragments. Microplastics are difficult to see with the naked eye and to biodegrade in marine environment, representing a problem since they can be ingested by plankton or other marine organisms, potentially entering the food web. An important source of microplastics appears to be through sewage contaminated by synthetic fibres from washing clothes. Since this phenomenon still lacks of a comprehensive analysis, the objective of this contribution was to investigate the role of washing processes of synthetic textiles on microplastic release. In particular, an analytical protocol was set up, based on the filtration of the washing water of synthetic fabrics and on the analysis of the filters by scanning electron microscopy. The quantification of the microfibre shedding from three different synthetic fabric types, woven polyester, knitted polyester, and woven polypropylene, during washing trials simulating domestic conditions, was achieved and statistically analysed. The highest release of microplastics was recorded for the wash of woven polyester and this phenomenon was correlated to the fabric characteristics. Moreover, the extent of microfibre release from woven polyester fabrics due to different detergents, washing parameters and industrial washes was evaluated. The number of microfibres released from a typical 5 kg wash load of polyester fabrics was estimated to be over 6,000,000 depending on the type of detergent used. The usage of a softener during washes reduces the number of microfibres released of more than 35%. The amount and size of the released microfibres confirm that they could not be totally retained by wastewater treatments plants, and potentially affect the aquatic environment.

Cotton fabric functionalisation with menthol/PCL micro- and nano-capsules for comfort improvement.

OBJECTIVE: Cotton functionalisation with poly-ɛ-caprolactone (PCL) micro- and nano-capsules containing menthol was carried out with the aim of introducing a long-lasting refreshing sensation. MATERIALS AND METHODS: The preparation of the polymer micro- and nano-capsules was carried out by solvent displacement technique. A confined impinging jets mixer was used in order to ensure fast mixing and generate a homogeneous environment where PCL and menthol can self-assemble. RESULTS: The micro- and nano-capsules and the functionalised fabrics were characterised by means of DSC, FT-IR spectroscopy and SEM imaging. Micro- and nano-capsules of different size, from about 200 to about 1200 nm, were obtained varying menthol to PCL ratio (from 0.76 to 8), overall concentration and flow rate (i.e. mixing conditions). The inclusion of menthol was confirmed by DSC analysis. DISCUSSION AND CONCLUSION: A patch test was carried out by 10 volunteers. Micro-capsules were found to be effective in conferring the fabric a refreshing sensation without altering skin physiology.

PTCA determination in human hair: reliability and analytical aspects.

BACKGROUND: In this study we analysed the reliability of HPLC determination of 2.3.5-pyrroletricarboxylic acid (PTCA). This product derives from oxidation of melanin in human hair, and is a good candidate as a risk marker for skin tumors. MATERIAL/METHODS: We determined PTCA in 100 melanoma cases and 100 controls, 21 replicates from six different reference hairs, two trace elements, and one reference sample (brown hair). RESULTS: Work-up procedures showed an almost perfect reproducibility with an Intraclass Correlation Coefficient (ICC) of 0.990. We noticed a low, detectable, but not statistically significant decrease in reproducibility proportional to the amount of PTCA. Agreement between determination following injection of the same solution in HPLC column was also high, with an overall ICC of 0.986. Simultaneous analysis of reproducibility showed a partial ICC for work-up (0.986), for injection (0.987), and an overall standardised ICC (0.975). The analysis of the two reference tracers in successive tests showed a weak, not statistically significant, decreasing linear drift, possibly due to various factors, such as aging of chemical solutions and HPLC columns. CONCLUSIONS: PTCA extracted from human hair through oxidation and determined with HPLC can be considered a reliable marker as a candidate for identifying persons at high risk for melanoma.

Near infrared spectroscopy as a tool for the determination of eumelanin in human hair.

Eumelanins are brown-black pigments present in the hair and in the epidermis which are acknowledged as protection factors against cell damage caused by ultraviolet radiation. The quantity of eumelanin present in hair has recently been put forward as a means of identifying subjects with a higher risk of skin tumours. For epidemiological studies, chromatographic methods of determining pyrrole-2,3,5-tricarboxylic acid (PTCA; the principal marker of eumelanin) are long, laborious and unsuitable for screening large populations. We suggest near infrared (NIR) spectroscopy as an alternative method of analysing eumelanin in hair samples. PCTA was determined on 93 samples of hair by means of oxidizing with hydrogen peroxide in a basic environment followed by chromatographic separation. The same 93 samples were then subjected to NIR spectrophotometric analysis. The spectra were obtained in reflectance mode on hair samples which had not undergone any preliminary treatment, but had simply been pressed and placed on the measuring window of the spectrophotometer. The PTCA values obtained by means of HPLC were correlated with the near infrared spectrum of the respective samples. A correlation between the PTCA values obtained by means of HPLC and the PTCA values obtained from an analysis of the spectra was obtained using the principal component regression (PCR) algorithm. The correlation obtained has a coefficient of regression (R(2)) of 0.89 and a standard error of prediction (SEP) of 13.8 for a mean value of 108.6 ng PTCA/mg hair. Some considerations about the accuracy of the obtained correlation and the main sources of error are made and some validation results are shown.

Degumming of silk fabric with several proteases.

A crêpe silk fabric was treated with different alkaline (3374-L, GC 897-H), neutral (3273-C), and acid (EC 3.4 23.18) proteases with the aim to study their effectiveness as degumming agents. Proteases were used under optimum conditions of pH and temperature, while enzyme dosage (0.05-2 U/g fabric) and treatment time (5-240 min) were changed in order to study the kinetics of sericin removal. Degumming loss with soap and alkali was 27 wt.%. The maximum amount of sericin removed in 1 h was 17.6, 24, and 19 wt.% for 3374-L (2 U/g fabric), GC 897-H (1U/g fabric), and 3273-C (0.1 U/g fabric), respectively. Under the experimental conditions adopted, EC 3.4 23.18 was almost ineffective as a degumming agent. Degumming loss increased as a function of the treatment time, reaching a value of 25 wt.% with 1 U/g fabric of 3374-L. The morphological analysis showed that sericin was completely removed from the warp yarns of the crêpe fabric, while the highly twisted weft yarns still exhibited the presence of sericin deposits within the most internal parts of the close fibre texture. The chromatographic pattern of soluble sericin peptides changed as a function of the kind of enzyme used, enzyme dosage, and treatment time. A mixture of peptides from 5 to 20 kDa in weight, with a weight-average molecular weight of about 12 kDa was obtained.