In situ quantification of poly(3-hydroxybutyrate) and biomass in Cupriavidus necator by a fluorescence spectroscopic assay

Fluorescence spectroscopy offers a cheap, simple, and fast approach to monitor poly(3-hydroxybutyrate) (PHB) formation, a biodegradable polymer belonging to the biodegradable polyester class polyhydroxyalkanoates. In the present study, a fluorescence and side scatter-based spectroscopic setup was developed to monitor in situ biomass, and PHB formation of biotechnological applied Cupriavidus necator strain. To establish PHB quantification of C. necator, the dyes 2,2-difluoro-4,6,8,10,12-pentamethyl-3-aza-1-azonia-2-boranuidatricyclo[7.3.0.03,7]dodeca-1(12),4,6,8,10-pentaene (BODIPY493/503), ethyl 5-methoxy-1,2-bis(3-methylbut-2-enyl)-3-oxoindole-2-carboxylate (LipidGreen2), and 9-(diethylamino)benzo[a]phenoxazin-5-one (Nile red) were compared with each other. Fluorescence staining efficacy was obtained through 3D-excitation-emission matrix and design of experiments. The coefficients of determination were ≥ 0.98 for all three dyes and linear to the high-pressure liquid chromatography obtained PHB content, and the side scatter to the biomass concentration. The fluorescence correlation models were further improved by the incorporation of the biomass-related side scatter. Afterward, the resulting regression fluorescence models were successfully applied to nitrogen-deficit, phosphor-deficit, and NaCl-stressed C. necator cultures. The highest transferability of the regression models was shown by using LipidGreen2. The novel approach opens a tailor-made way for a fast and simultaneous detection of the crucial biotechnological parameters biomass and PHB content during fermentation. Key points • Intracellular quantification of PHB and biomass using fluorescence spectroscopy. • Optimizing fluorescence staining conditions and 3D-excitation-emission matrix. • PHB was best obtained by LipidGreen2, followed by BODIPDY493/503 and Nile red. Graphical abstract

Treatment of Dry Eye With Intracanalicular Injection of Hydroxybutyl Chitosan: A Prospective Randomized Clinical Trial

Background: Punctal/intracanalicular plugs on the market nowadays are all designed before clinical use in treating dry eye disease (DED). To provide an individualized lacrimal drainage system occlusion method and reduce the complications, we developed a “liquid plug” strategy by intracanalicular injection of hydroxybutyl chitosan (HBC) solution, a thermosensitive, phase-changing biomaterial. This study evaluated the efficacy and safety of the HBC plug in treating dry eye disease by comparing it with the VisiPlug absorbable intracanalicular plug.Methods: A monocenter, randomized, controlled clinical trial was performed. Fifty patients with DED were randomized 1:1 to undergo either the HBC injection treatment or the VisiPlug treatment. Ocular Surface Disease Index (OSDI) questionnaire, tear break-up time (TBUT), corneal fluorescence staining (CFS), tear meniscus height (TMH), and phenol red thread test were evaluated at Day 0 (baseline, before treatment) and Weeks 1, 4, and 12.Results: The two groups had a balanced baseline of age, gender, and DED-related characteristics. Both occlusion methods could relieve the symptoms and signs of DED. Significant improvement was found in OSDI, phenol red thread test, and tear meniscus height (P < 0.05 compared to baseline) but not in corneal fluorescence staining and tear break-up time (P > 0.05). There is no statistically significant difference between HBC injection and VisiPlug at Weeks 1 and 4 (P > 0.05). However, at week 12, the HBC injection was not as effective as the VisiPlug in maintaining phenol red thread test (HBC: 5.35 ± 3.22 mm, VisiPlug: 8.59 ± 4.35 mm, P = 0.009) and tear meniscus height (HBC: 206.9 ± 47.95 μm, VisiPlug: 242.59 ± 60.30 μm, P = 0.041). The numbers of ocular adverse events were relatively low in both groups.Conclusions: The HBC injection showed similar efficacy and safety compared to VisiPlug. The intracanalicular injection of HBC solution proves to be a promising, individualizing method to treat DED.Clinical Trial Registration: This study is registered with the Chinese Clinical Trial Registry (https://www.chictr.org.cn/enindex.aspx), Identifier: ChiCTR1800016603.

What have we known so far for fluorescence staining and quantification of microplastics: A tutorial review

Understanding the fate and toxicity of microplastics (MPs, < 5 mm plastic particles) is limited by quantification methods. This paper summarizes the methods in use and presents new ones. First, sampling and pretreatment processes of MPs, including sample collection, digestion, density separation, and quality control are reviewed. Then the promising and convenient staining procedures and quantification methods for MPs using fluorescence dyes are reviewed. The factors that influence the staining of MPs, including their physicochemical properties, are summarized to provide an optimal operation procedure. In general, the digestion step is crucial to eliminate natural organic matter (NOM) to avoid interference in quantification. Chloroform was reported to be the most appropriate solvent, and 10–20 μg/mL are recommended as optimal dye concentrations. In addition, a heating and cooling procedure is recommended to maintain the fluorescence intensity of MPs for two months. After staining, a fluorescence microscope is usually used to characterize the morphology, mass, or number of MPs, but compositional analysis cannot be determined with it. These fluorescence staining methods have been implemented to study MP abundance, transport, and toxicity and have been combined with other chemical characterization techniques, such as Fourier transform infrared spectroscopy and Raman spectroscopy. More studies are needed to focus on the synthesis of novel dyes to avoid NOM’s interference. They need to be combined with other spectroscopic techniques to characterize plastic composition and to develop image-analysis methods. The stability of stained MPs needs to be improved.

FLGS-03. Fluorescein sodium-guided biopsy or resection in patients with contrast enhancing brainstem lesion in MRI

BACKGROUND It is challenging to resect or just biopsy the lesions in the brainstem, due to the essential function of the surfaces and limited space. Neuro-navigation is not always reliable and stereotatic biopsy is infrequently inconclusive due to small or inadequate samples. We want to share our experiences in the application of fluorescein sodium in surgery on patients with brainstem lesion which is contrast enhancing in MRI. METHODS Between January 2017 and June 2021, 5 patients with brainstem lesion underwent fluorescein sodium-guided surgery in neurosurgery department of Sun Yat-sen University Cancer Center. After injection of low dose of sodium fluorescein (3 mg/kg), the lesions with strong fluorescence staining were identified as the target area for biopsy or resection. RESULTS 5 consecutive patients (aged 6–47 years) with brainstem lesions prospectively underwent fluorescein sodium-guided surgery. The lesions were located in pontine in 3 patients and in the medulla in 2 patients. Gross total resection was achieved in 2 patients, and partial resection in the other 3 patients. In all patients, a pathological diagnosis was obtained (4 gliomas and 1 metastasis from non-small cell lung carcinoma) without severe complications, including mild facial or abduct nerve palsy in 3 patients. And all the specimens with strong fluorescence staining sent for pathology were proved to be tumorous. CONCLUSION Fluorescein sodium-guided technique was helpful to locate the lesion in brainstem which was contrast-enhanced in MRI. It was effective and safe to figure out an ideal trajectory to avoid damage of the crucial structures and improve the diagnostic rate.

Study on Multi-Dimensional Optimization of Detailed Laboratory Analysis Method for Ship Ballast Water

Ballast water can bring aquatic organisms into foreign ecosystems and cause the risk of biological invasion. Therefore, it needs to be treated before discharge, and the treated water needs to be analyzed to determine whether it meets the specified standard. At present, there is no unified method for the detection of plankton worldwide, and there are some problems in the existing methods, such as unreasonable and inaccurate. In this study, neutral red (NR), 5-chloromethyfluorescein diacetate (CMFDA) and fluorescein diacetate (FDA) were used to dye the 10-50 µm plankton of three common phyla in ballast water, and were determined by fluorescence microscope. The results showed that for 10-50 µm plankton, the staining effect of double fluorescence staining was obvious, while the fluorescent dyes could only stain part of marine diatoms, and the sample could not be fixed. The optimal dyeing concentration of neutral red was 1/5000, the dyeing time was 20 min, and the overall dyeing efficiency was above 99%. Fixing agent was used after neutral red staining, when fixing with Lugol’s solution, the lower the temperature, the better the preservation effect. At -4 °C, the storage time of the sample could be increased to 12 h, and the proportion of plankton was more than 96%. In conclusion, neutral red staining can be used as a supplement to fluorescence staining, and the the storage time of samples can be prolong by pretreatment and fixation the samples.

Accumulation of Abnormal Amyloplasts in Pulp Cells Induces Bitter Pit in Malus domestica

Apple bitter pit primarily occurs during fruit ripening and storage; however, its formation mechanism remains unclear. Although it is considered that Ca2+ deficiency causes metabolic disorders in apples, there have been few studies on the mechanism of the bitter pit from the perspective of cell structure. At the fruit ripening stage, the fruit with a bitter pit on the tree was taken as the research material. In this study, the microscopic observation revealed numerous amyloplasts in the pulp cells of apples affected with bitter pit, but not in the healthy pulp. Furthermore, the results of fluorescence staining and transmission electron microscopy (TEM) revealed that the bitter pit pulp cells undergo programmed cell death (PCD), their nuclear chromosomes condense, and amyloplast forms autophagy. The cytoplasmic Ca2+ concentration in the healthy fruits was lowest near the peduncle, followed by that in the calyx, whereas it was highest at the equator. In contrast, the cytoplasmic Ca2+ concentration in apple fruits showing bitter pit disorder was lowest near the peduncle and highest in the calyx. Moreover, the cytosolic Ca2+ concentration in the flesh cells of apples with the bitter pit was much lower than that in the healthy apple flesh cells; however, the concentration of Ca2+ in the vacuoles of fruits with the bitter pit was higher than that in the vacuoles of healthy fruits. In summary, bitter pit pulp cells contain a large number of amyloplasts, which disrupts the distribution of Ca2+ in the pulp cells and causes PCD. These two processes lead to an imbalance in cell metabolism and induce the formation of a bitter pit.

Apoptin Causes Apoptosis in HepG-2 Cells by Inducing Stress Injury in the Endoplasmic Reticulum

Apoptin is derived from the chicken anemia virus and exhibits specific cytotoxic effects against tumor cells. In our previous study, we demonstrated that Apoptin induced significant changes in the expression levels of endoplasmic reticulum stress (ERS) related proteins and caused a strong and lasting ERS response. The aim of this study was to explore the effects of ERS injury induced by Apoptin on the endoplasmic reticulum (ER) and the apoptotic pathway in mitochondria. ERS injury induced the intracellular levels of calcium (Ca2+) were determined by electron microscopy, flow cytometry and fluorescence staining. Mitochondrial injury was determined by mitochondrial membrane potential and electron microscopy. The relationship between Ca2+ level and mitochondrial injury on Apoptin-treating cells was analyzed using Ca2+ chelator, flow cytometry and fluorescence staining. Western blotting was used to investigate the levels of key proteins in the ER and the apoptotic pathway in mitochondria. We also investigated the in vivo effects of ERS injury on the ER and the mitochondrial apoptotic pathway via the immunohistochemical analysis of tumor tissues from HepG-2 cells acquired from nude mice undergoing xenografts. In vitro and in vivo experiments showed that Apoptin caused ERS injury and an imbalance in Ca2+, damaged the structure of the mitochondria, and increased the expression levels of Caspase-12, CHOP, AIF, HtrA2, Smac/Diablo, and Cyto-C. In summary, Apoptin induced apoptosis in HepG-2 cells via ERS and the mitochondrial apoptotic pathway. This study showed that Apoptin induced apoptosis in HepG-2 cells via ERS injury.