Abstract
Polymeric nanoparticles, which show aggregation-induced luminescence emission, have been successfully prepared from larch bark, a natural renewable biomass resource, in a simple, rapid ultrasonic fragmentation method. The structure, element, particle size and molecular weight distribution of larch bark extracts (LBE) were studied by FTIR, XPS, TEM, XRD and linear mode mass spectrometry, respectively. LBE was found containing large numbers of aromatic rings, displaying an average particle size of about 4.5 nm and mainly presenting tetramers proanthocyanidins. High concentration, poor solvent, low temperature and high viscosity restricted the rotation and vibration of the aromatic rings in LBE, leading to the formation of J-aggregates and enhancing the aggregation-induced fluorescence emission. LBE possessed good resistance to photobleaching under ultraviolet light (200 mW/m2). Cytotoxicity experiments for 24 h and flow cytometry experiments for 3 days proved that even the concentrations of LBE as high as 1 mg/mL displayed non-toxic to MG-63 cells. Therefore, LBE could be employed for MG-63 cell imaging, with similar nuclear staining to the DAPI. The effects of different metal ions on the fluorescence emission intensity of LBE were analyzed and exhibited that Fe3+ owned obvious fluorescence quenching effect on LBE, while other metal ions possessed little or weak effect. Furthermore, the limit of detection (LOD) of Fe3+ was evaluated as 0.17 μM.
Highlights
Larch bark extracts (LBE) containing oligomeric proanthocyanidins was extracted from larch bark using the ultrasonic crushing method, with 40% aqueous ethanol as the extraction solvent and (Jiang et al, 2016; Luo et al, 2019), through dialysis (3,500 Dalton) and freeze-drying
The structure of larch bark extracts (LBE) was analyzed by FT-IR spectroscopy, X-ray photoelectron spectroscopy (XPS), UV spectroscopy and mass spectrometry
The molecular weight distribution of LBE was analyzed by linear mode MALDI-TOF mass spectrometry after deionization and addition of Cs3+ as cationic reagent (Shoji et al, 2006; María et al, 2010; Jara and Josep, 2012)
Summary
Fluorescent nanoparticles, including organic molecules (Lou et al, 2016; Zhang et al, 2017) graphene quantum dots (Zhu et al, 2016) and carbon dots (Wang et al, 2014; Chang et al, 2019), possess low toxicity and good biocompatibility, and are resistant to photobleaching, which exhibit enormous potential in cellular and in vivo imaging (Wang et al, 2013; Ding et al, 2016, 2018; He et al, 2018), as fluorescent probes (Qu et al, 2013; Zhang et al, 2014; Li et al, 2019a; Qi et al, 2019), in light-emitting diodes (Chiang et al, 2005; Lee et al, 2016; Tachibana et al, 2017; Liu et al, 2018; Wu et al, 2019), as ultraviolet and blue light blockers (Park et al, 2019)Biomass-Based Polymer Nanoparticles and for the detection of counterfeit materials (Chen et al, 2017). Organic molecules fluorescent nanoparticles are most commonly used in the field of cellular imaging and fluorescent probes. Much progress have been made in the study of fluorescent nanoparticles based on organic molecules, many challenges remain still to be accomplished. Most small molecule-based and polymeric fluorescent nanoparticles require expensive and time-consuming synthesis and toxic reagents, which limit their wide applications. The preparation of polymeric nanoparticles with AIE property by simple extraction of renewable natural raw material would be very attractive, which was paid little concern. The green and cheap larch bark was chosen as the raw material to produce polymeric nanoparticles with AIE property. Our method for producing natural polymeric nanoparticles with AIE from the rational use of larch bark, could be regarded as a process turning waste into wealth
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