BACKGROUND: Polydimethylsiloxane (PDMS) is widely used in the basic research on cell biology because of its good biocompatibility and ability to be processed at the micro/nano level. However, cell culture on PDMS has been generally compromised by its strong hydrophobicity.OBJECTIVE: To perform a comparative investigation on the influences of different surface modifications as well as stiffness of PDMS on cellular behaviors.METHODS: PDMS films with varying stiffnesses were subjected to various surface modifications, including serum incubation, type I collagen deposition and air plasma treatment. Bovine articular chondrocytes were seeded on PDMS films and cell adhesion, proliferation and matrix production were characterized using F-actin staining, cell counting kit-8,microscopic examination, Sirius red/Safranin-O staining and quantitative determination of glycosaminoglycans,respectively.RESULTS AND CONCLUSION: Serum incubation, type I collagen deposition and air plasma treatment were all found to promote adhesion and proliferation of bovine articular chondrocytes from the results of F-actin staining and cell prolifereration curve, with air plasma treatment the best. Total amount of glycosaminoglycans (GAG) secretion was only increased by air plasma treatment and GAG/DNA was decreased by all modifications. Stiffness also played roles in cell adhesion, proliferation and GAG production, which was found to be dependent on surface modifications. This study would provide guidance for applying PDMS in cell culture.

Objective:To investigate the effects of CT images reconstructed using different field of view (FOV) sizes on the automatic segmentation of organs at risk and dose calculation accuracy in radiotherapy after radical mastectomy.Methods:Under the same scanning conditions, CT values-electron density conversion curves were established by reconstructing the original CT images of a phantom placed at the isocenter and extended FOV (eFOV) positions using FOV sizes of 50, 60, 70 and 80 cm. Then, these curves were compared. A standard phantom with a known volume was scanned, and the automatic segmentation result of the phantom on CT images reconstructed using different FOV sizes was compared. A total of 30 patients in Guangdong Second Provincial General Hospital from January 2020 to June 2022 with breast cancer were randomly selected. Through simulated positioning, their CT images were reconstructed using different FOV sizes for the purpose of automatic segmentation of organs at risk, followed by comparison between the outcomes of automatic segmentation and physicians′segmentation. The treatment plan established based on CT images reconstructed using a FOV size of 50 cm (FOV 50 images for short) was applied to CT images reconstructed using FOV sizes of 60, 70 and 80 cm (FOV 60, FOV 70 and FOV 80 images for short) for dose calculation, and the dose calculation result were compared. Results:The CT values - electron density conversion curves derived from CT images reconstructed using different FOV sizes were roughly consistent. At the isocenter, the difference between the segmented volume and actual volume of the standard phantom increased up to a maximum of 6 cm 3 (4.8%) with an increase in the FOV size. As indicated by the automatic segmentation result, the segmentation accuracy of the spinal cord, trachea, esophagus, thyroid, healthy mammary gland, and skin decreased with an increase in the FOV size ( t = -28.43-8.23, P < 0.05). The comparison of dose calculated based on CT images reconstructed using different FOV sizes showed that there was no statistically significant differences( P>0.05) in the dose to target volume ( V95) and the maximum and average doses in the supraclavicular lymph node region, as well as the dose to organs at risk. The coverage for planned target volume decreased with an increase in the FOV size, with a maximum difference of 4.06%. Conclusions:It is recommended that, for radiotherapy after radical mastectomy, FOV 50 images should be selected for the automatic segmentation of organs at risk, CT-values-electron density conversion curves should be established based on the electron density phantom images of the eFOV region, and the eFOV 80 images should be preferred for dose calculation.

Objective:To identify the pathogens isolated in the subperiosteal abscesses from the pediatric patients with acute osteomyelitis and to investigate the characteristics of bacterial drug resistance.Methods:A retrospective study was conducted on children with acute septic osteomyelitis who were hospitalized in the Children's Hospital, Zhejiang University School of Medicine from January 1, 2011 to March 1, 2018. The results of bacterial cultures isolated from the subperiosteal abscesses or bone marrow fluid were collected. The Merier automatic bacterial identification system (i.e., Vitek) was used to identify the bacteria and to assess the drug sensitivity.Results:(1) A total of 104 pediatric patients were included and 60 (57.7%) were male. Sixty-six strains of pathogens were isolated from 65 patients (62.5%). Among them, 53 strains (51.0%) were Staphylococcus aureus; 3 strains were Escherichia coli; 2 strains (1.9%) were Pseudomonas aeruginosa; 2 strains (1.9%) were Streptococcus pneumoniae, 2 strains (1.9%) were Ochrobactrum anthropi, and 4 strains (3.8%) were other bacteria. Pathogens were not found in 39 patients (37.5%). (2) Staphylococcus aureus accounted for 81.5% (53/65) of the pathogen-positive cases. Among them, 23 strains (43.4%) were methicillin-resistant Staphylococcus aureus (MRSA). Aureus-positive children were statistically significantly older ( P=0.028), heavier ( P=0.040) and had higher C-reactive protein (CRP) level ( P=0.038) than the aureus-negative children. (3) All the 53 Staphylococcus aureus strains were resistant to penicillin and 56.6% of them were only sensitive to benzocillin. The resistance rates to compound sulfamethoxazole, tetracycline, clindamycin and erythromycin were 11.3%, 30.2%, 67.9% and 69.8%, respectively. The sensitivity rate of the strains to furantoin was 90.2%. All strains were sensitive to quinupristin/dalfopristin, linezolid, rifampicin, tigecycline, levofloxacin, moxifloxacin, ciprofloxacin and vancomycin. There was 69.8% of the strains resistant to three or more different types of antibiotics. Conclusions:Staphylococcus aureus is the most common pathogen that causes the acute septic osteomyelitis in children, and the resistance rate to Benzocillin is relatively high. Therefore, Benzocillin and Clindamycin, as the traditionally-used drugs, should not be considered as the first choice when empirically using intravenous antibiotics. In the present study, pathogens in 39 patients (37.5%) were not detected in their subperiosteal abscesses or bone marrow fluid, so further effort should be made to investigate the etiology of these patients.