Polystyrene Encapsulated SERS Tags as Promising Standard Tools: Simple and Universal in Synthesis; Highly Sensitive and Ultrastable for Bioimaging.

Surface coating determined the sensitivity and stability of surface-enhanced Raman scattering (SERS) tags in bioanalysis. The reported various coatings suffered from the drawbacks of a lack of rigidity, stability, or synthesis versatility. Herein, we demonstrated robust polystyrene (PS) coated SERS tags that could be prepared by an easy and universal approach. Taking advantages of biocompatible, transparent, compact properties of PS shell, the coated tags showed satisfactory sensitivity, biocompatibility, and superior structural stability in cell and in vivo imaging applications. More importantly, the PS coating strategy allowed for the encapsulation of SERS tags encoded with not only thiolated but also nonthiolated Raman reporters without loss of sensitivity, as exemplified in the synthesis of 9 different resonant dye-encoded tags. Moreover, the coating of SERS tags with various kinds of substrates was achieved via the same standard protocol. Comparing with widespread silica coated tags, the PS coated ones were more stable in harsh conditions and had an easily expanded ultrasensitive (resonant) tags library with much lower cost (no need of expensive sulfhydryl/isothiocyano reporters with limited types), illustrating great promise as standard analytical tools of commercialized value for bioanalysis, medical diagnostics, and environmental science studies.

Polystyrene nanoplastics demonstrate high structural stability in vivo: A comparative study with silica nanoparticles via SERS tag labeling.

Nanoplastics are regarded as inert particulate pollutants pose potential threat to organisms. It has been verified that they can penetrate biological barriers and accumulate in organisms; however, there is still a knowledge gap on the in vivo stability and degradation behaviors due to the lack of ideal analytical methods. Herein, a surface-enhanced Raman scattering (SERS) tag labeling technique was developed to study the in vivo behaviors of polystyrene (PS) nanoplastics by comparison with silica (SiO2) nanoparticles (NPs). The labeled NPs were composed of gold NP core, attached Raman reporters as well as PS and silica shell, respectively, demonstrating strong SERS signals which were responsive to the compactness of the shells. The labeled NPs enabled the probing of in vivo structural stability of PS and silica in the liver, spleen and lung of mice after intravenous injection via the time-dependent evolution of SERS signal intensity and gold element content in the organs. The results indicated that both PS and silica model NPs retained in these organs without apparent excretion within 28 d. However, the structural stabilities of PS and silica differed dramatically as reflected by the SERS signal and tissue slice characterization. The silica shell completely degraded whereas the PS shell was still compact. Our results verified the long-term accumulation and in vivo inert property of nanoplastics, hinting that they were distinct from natural NPs and probably induce higher health risks from the aspect of the non-degradation property.

Surface-enhanced Raman scattering labeled nanoplastic models for reliable bio-nano interaction investigations.

Nanoplastics (NPs) have attracted great attention as an emerging pollution. To date, their interaction with biological systems has been studied mostly by using fluorescent-labeled NPs, which suffered from serious drawbacks such as biological autofluorescence interference and false-positive results. Reliable optically labeled NP models are eagerly desired until now. Herein, a novel near-infrared (NIR) surface-enhanced Raman scattering (SERS) labeled NP model was proposed, which gained single-particle ultra-sensitivity, deep tissue detection, multiplex labeling ability, and anti-interference property. More importantly, the NP demonstrated satisfactory in vivo signal stability which completely prevented the positive-false problems. The advantages of the NPs enabled direct, dynamic in vivo behavior imaging study in living zebrafish embryo, adult zebrafish and green vegetable Brassica rapa. It was found for the first time that NPs entered blood circulation system of zebrafish larva via dermal uptake route, which only occurred in a short 48 h-window post-hatch. NPs widely distributed in roots, shoots and leaves of Brassica rapa seedlings germinating and growing in the NP-containing hydroponic culture. Different depths of one root showed varied adsorption capabilities towards NPs with fulvic acid, lipid and sodium dodecyl sulfate eco-coronas. This work provided an ideal tool for reliable bio-NP interaction study for a variety of organisms, which could promote the research of NPs.

Quantitative assessment of in vivo distribution of nanoplastics in bivalve Ruditapes philippinarum using reliable SERS tag-labeled nanoplastic models.

Nanoplastics (NPs) as emerging marine pollutants can be taken up by seafood organisms. It is crucial to quantitatively assess NP's distribution behavior in organisms to elucidate concentration dependent biological effects. Such a knowledge gap has remained due to the lack of reliable NP models and analytical methods. Herein, surface enhanced Raman scattering (SERS)-labeled NP models were developed and their bioavailability, distribution and accumulation in Ruditapes philippinarum, a typical marine bivalve, were quantitatively studied. Taking advantage of the sensitive and characteristic SERS signals of the NP models, distribution could be quickly and accurately obtained by the Raman imaging technique. Moreover, quantitative analysis of NPs could be performed by the detection of gold element contents via inductively coupled plasma mass spectroscopy (ICP-MS) detection. ICP-MS results revealed that after 3 days exposure of monodispersed NPs (100 nm, 0.2 mg L-1), the digestive gland accumulated 86.7% of whole-body NPs followed by gill (5.2%), mantle (5.1%), foot (1.3%), exhalant siphon (1.1%), and adductor (0.6%). Upon 11 days depuration, 98.7% of NPs in the digestive gland were excreted, whereas the clearance ratios in other organs were much lower. NP aggregates (around 1.5 µm) demonstrated similar distribution and clearance trends to the monodispersed ones. However, the accumulation amount in each organ was 15.2% to 77.6% lower. Surface adherence and passive ingestion routes resulted in NP accumulation, which contributed to the comparable NP abundance in these organs. Additionally, boiling treatment (mimicking a cooking process) did not decrease the NP amount in these organs. This work provided a dual-mode and quantitative analysis protocol for NPs for the first time, and suggested the risk of NP uptake by humans via bivalve seafood diets.