O-008 Low grade blastocysts result in healthy live births and should not be discarded

Study question

Does transfer of low grade blastocysts results in acceptable live birth rates the birth of healthy babies?

Summary answer

While BC/CB/CC blastocysts have a reduced chance of live birth compared with AA/AB/BA/BB blastocysts, the absolute chances are still reasonable.

What is known already

Transfer of poorer quality embryos and blastocysts result in lower live birth rates, though to what extent is unclear, nor if there is an absolute threshold below which live births are very rare or even do not occur. Further, the developmental competence of the inner cell mass (ICM) or trophectoderm (TE) could at least theoretically impact the pregnancy and/or the health of the baby. Many clinics do not transfer or freeze poor quality embryos and blastocysts, and prefer to submit the patient to a further stimulation cycle.

Study design, size, duration

We performed a retrospective analysis of 10,978 couples undergoing singleton blastocyst transfers between 2009 and March 2020. We included all single blastocyst transfers for which there was complete data on blastocyst quality, singleton or twin births, birthweight and gestation at delivery, irrespective of blastocyst grading, female age, cause of infertility, ovarian response or endometrial thickness. We recorded live birth rates, birth weight and gestational age.

Participants/materials, setting, methods

Data from 14 clinics in 3 countries, 8 from China, 5 from New Zealand, and 1 from Australia were included in the final dataset. We compared the impact of blastocyst grading using multiple logistic regression. Blastocyst grading was based on the Gardner classification, in which the first letter denotes the grade of the inner cell mass (A is best), and the second letter the grade of the trophectoderm.

Main results and the role of chance

Overall, 10,978 single blastocyst cycles resulted in 4,261 live births (38.8%) (4195 singletons and 132 twins). Live birth rates were 47% after transfer of AA blastocysts (n = 2306); 42% after AB/BA (n = 2088); 33% after BC (n = 1973); 25% after CB (n = 715) and 14% after CC (n = 117). There were too few AC (n = 27) or CA (n = 12) blastocysts to include in the analysis. The odds of live birth for BC/CB/CC blastocysts compared with AA/AB/BA blastocysts, vary between 0.8 and 0.9.

The live birth rate appears to be more dependent on ICM quality (C grade, n = 844, 23.2%) rather than TE quality (C grade, n = 2117, 32.1%), with the odds of live birth 0.43 and 0.57 respectively compared to A grade ICM or TE.

The average birth weight (singleton only) was 3336.9+/-570.3 g (range 3323 to 3386 g), and the average gestation at delivery (singleton only) was 38+6+/-2.0 weeks (range 38+2 to 39+1). There was no significant difference for birth weight or gestational age at delivery between blastocysts of different grades.

Limitations, reasons for caution

This was a retrospective study. Grading was based on inner cell mass and trophectoderm and not on degree of expansion, or on day of transfer.

It is likely that higher quality blastocysts were transferred first, in a fresh cycle, and poorer quality blastocysts frozen for later transfer.

Wider implications of the findings

The most important finding is that reasonable live birth rates are obtained in CC-blastocysts.

We therefore advocate that CC-blastocysts should be replaced or frozen for later transfer. It is reassuring that there was no impact of blastocyst quality on birth weights or gestational age at the time of delivery.

Trial registration number

Not applicable

The Influence of Trait Emotion and Spatial Distance on Risky Choice Under the Framework of Gain and Loss

In the time of the COVID-19 pandemic, people are often faced with uncertain risky choice. Risky choice will be affected by different descriptions of the event's gain or loss framework, this phenomenon is known as the framing effect. With the continuous expansion and in-depth study of frame effects in the field of risky choice, researchers have found that the are quite different in different situations. People have different interpretations of the same event at different psychological distances, and will also be affected by their own emotions. Therefore, the current study examines the common influence of task frame, spatial distance, and trait emotion on risky choice through two studies. Study 1 used a 2 (framework: gain vs. loss) × 2 (trait sentiment: high vs. low) inter-subject design, and the dependent variable is the choice of the rescue plan for the classic "Asian disease" problem. The results revealed that trait anger did not predict individuals' risky choice preferences, and high trait anxiety led individuals to be more risk-averse. The framing effect exists in risky choice, and individuals prefer risk seeking in the loss frame. Study 2 used a 2 (spatial distance: distant vs. proximal) × 2 (framework: gain vs. loss) × 2 (trait sentiment: high vs. low) three-factor inter-subject design in which the dependent variable is the choice of rescue plan. The results indicate that the framing effect also exists in risky choice, and individuals prefer risk seeking in a loss frame. High trait anxiety lead individuals to be more risk-averse, while trait anger has no significant predictive effect on risk preference. Distant spatial distance lead individuals to increase their preference for risk-seeking under the gain frame, which leads to the disappearance of the framing effect. In conclusion, trait anxiety and spatial distance have a certain degree of influence on risky choice under the framework of gain and loss.

[Disease spectrum analysis of children with inherited metabolic diseases detected by gas chromatography-mass spectrometry of urinary organic acids]

Objective: To investigate the spectrum of amino acid, organic acid, and fatty acid oxidative metabolic diseases in children diagnosed by detecting urinary organic acid levels using gas chromatography-mass spectrometry. Methods: From January 2005 to December 2021, clinical data of 2 461 children diagnosed with inherited metabolic diseases (IMD) by gas chromatography-mass spectrometry, in combination with tandem mass spectrometry and genetic testing in Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine were retrospectively analyzed. Results: Among 2 461 children, 1 446 were male and 1 051 were female. A total of 32 types of IMD were detected among 2 461 patients, which included 10 amino acid disorders in 662 cases (26.9%), 6 common diseases were hyperphenylalaninemia, citrin deficiency, ornithine carbamoyltransferase deficiency, maple syrup urine disease, alkaptonuria, and tyrosinemia-I, 17 types of organic acidemias in 1 683 cases (68.4%), 6 common diseases were methylmalonic acidemia, propionic acidemia, valeric acidemia-type Ⅰ, isovaleric acidemia, 3-methylcrotonyl-CoA carboxylase deficiency and multiple carboxylase deficiency and 5 fatty acid β oxidative defects in 116 cases (4.7%), 2 common diseases were multiple acyl-CoA dehydrogenase deficiency and short-chain acyl-CoA dehydrogenase deficiency). Conclusion: Among the diseases diagnosed by analyzing urinary organic acid profiling with gas chromatography-mass spectrometry, the most common are organic acidemias, followed by amino acid disorders and fatty acid oxidation defects.

[Risk factors of residual tumor in single small hepatocellular carcinoma after thermal ablation treatment]

Objective: To evaluate the risk factors of residual tumor after thermal ablation in patients with small hepatocellular carcinoma. Methods: This was a retrospective study recruiting 107 patients diagnosed as single hepatocellular carcinoma with maximum diameter ≤3 cm from December 2009 to August 2015 in National Cancer Center. The cohort enrolled 81 males and 26 females, including 83 patients younger than 70 years old. All patients were treated with radiofrequency ablation or microwave ablation, and evaluated by CT or MRI after 4-6 weeks compared with baseline data. Potentially related factors were analyzed such as patients' characteristics, tumor location and adjacent, ablation pattern, hepatitis B/C infection. A multivariate logistic regression analysis was conducted for the independence of risk factors. Results: Six patients (5.6%) with residual tumor was detected in the whole population of 101 cases. Univariate analysis suggested that tumor adjacent to vascular structure, poor differentiation, AFP≥200 μg/L were the risk factors of residue disease (all P<0.05). Multivariate logistic regression suggested that pathological type of poorly differentiated tumor was the only independent risk factor (HR=2.26,95%CI 0.25-20.50, P=0.030). Conclusions: Poorly differentiated pathology is an independent predictive factor for residual disease in small hepatocellular carcinoma after thermal ablation. Such patients should be routinely followed up after operation.

Significance of miRNA in enhancement of flavonoid biosynthesis

Flavonoid metabolism shows very strong plasticity in plant development and coping with the changing environment. Flavonoid biosynthesis is regulated by many metabolic pathways, including transcriptional regulation, post-transcriptional control, post-translational regulationand epigenetic regulation. miRNA is a form of endogenous noncoding single-strand small molecule RNA that primarily regulates the expression of target genes horizontally after transcription through splicing and translational suppression. It also plays an important role in regulating plant growth and development, secondary metabolism and biotic and abiotic stress. miRNA can regulate the formation of flavonoids by acting on structural genes or indirectly by using an MBW transcription complex comprising MYB-bHLH-WD40. This study summarizes the biosynthesis and mechanisms of miRNA, and provides a summary of the mechanisms of miRNAs involved in production of flavonoids, in order to elucidate the biosynthesis pathway and complex regulatory network of plant flavonoids. We aim to provide new insights into improving the content of flavonoid active ingredients in plants.

Interface effects of Schottky devices built from MoS2and high work function metals

Schottky junctions, formed by high work function metals and semiconductors, are important devices in electronics and optoelectronics. The metal deposition in traditional Schottky interfaces usually damages the semiconductor surface and causes defect states, which reduces the Schottky barrier height and device performance. This can be avoided in the atomically smooth interface formed by two-dimensional (2D) metals and semiconductors. For better interface tailoring engineering, it is particularly important to understand various interface effects in such 2D Schottky devices under critical or boundary conditions. Here we report the fabrication and testing of three types of MoS₂devices, i.e., using PtTe₂, Cr and Au as contact materials. While the Cr/MoS₂contact is an ohmic contact, the other two are Schottky contacts. The van-der-Waals interface of PtTe₂-MoS₂results in a well-defined OFF state and a significant rectification ratio of 10⁴. This parameter, together with an ideality factor 2.1, outperforms the device based on evaporated Au. Moreover, a device in the intermediate condition is also presented. An abrupt increase in the reverse current is observed and understood based on the enhanced tunneling current. Our work manifests the essential role of doping concentration and provides another example for 2D Schottky interface design.

Impacts of Stress and Risk Perception on Mental Health of College Students During the COVID-19 Pandemic: The Mediating Role of Coping Efficacy

OBJECT

In this study, we aimed to explore the influences of pandemic stress, risk perception, and coping efficacy on the mental health of Chinese college students during the COVID-19 pandemic.

METHODS

A nationally representative sample of Chinese college students (N = 3,381, M age = 20.85, SD age = 1.31) took part in an online survey during the COVID-19 pandemic. Correlation coefficients, structural equation modeling, and other statistical analysis methods were used for data analysis.

RESULTS

(1) The Chinese college students' pandemic stress and perceived pandemic risk were found to be moderate (3.51 ± 0.83, 3.45 ± 0.94), whereas their perceived infection risk was lower (2.10 ± 0.67). Their mental health during the COVID-19 pandemic was found to be good (3.80 ± 0.73). (2) The quality of their mental health was significantly and negatively associated with pandemic stress, perceived pandemic risk, and perceived infection risk. The level of their mental health was significantly and positively associated with coping efficacy, and their coping efficacy was significantly and negatively associated with pandemic stress, perceived pandemic risk, and perceived infection risk.

CONCLUSION

Coping efficacy played a partial mediating role in the relationship between pandemic stress and mental health, coping efficacy played a partial mediating role in the relationship between perceived infection risk and mental health, and coping efficacy played a complete mediating role in the relationship between perceived pandemic risk and mental health. Our findings show the importance of fostering college students' coping efficacy to improve their mental health during the COVID-19 pandemic.

Association of Loss of Occlusal Pairs of Teeth with Sarcopenia in a Chinese Population of Community-Dwelling Elderly

OBJECTIVES

Tooth loss, which usually leads to malnutrition, is common in the elderly. However, limited information is available regarding its association with sarcopenia. This study aimed to investigate the relationship between loss of occlusal pairs of tooth and sarcopenia.

DESIGN

A cross-sectional retrospective study was performed.

SETTING

The elderly who participated in the National Basic Public Health Project in the Maigaoqiao Community Medical Center in Nanjing, Jiangsu Province, China.

PARTICIPANTS

A total of 2850 individuals aged ≥60 years were enrolled.

MEASUREMENTS

Sarcopenia was defined according to the criteria proposed by the Asian Working Group for Sarcopenia. A trained dentist assessed oral health status and counted the number of present teeth. Logistic regression analyses were performed to evaluate the association between the loss of occlusal pairs and sarcopenia.

RESULTS

The prevalence of sarcopenia was 7.1% (201/2850). Univariate logistic regression analysis showed that loss of occlusal pairs was associated with sarcopenia [anterior occlusal pairs (AOPs): odd ratio (OR) = 1.292, 95% confidence interval (CI) = 1.158-1.442; posterior occlusal pairs (POPs): OR = 1.147, 95% CI = 1.018-1.221]. Multivariate logistic regression analysis indicated that loss of POPs was still an independent risk for sarcopenia (OR = 1.108, 95% CI = 1.007-1.220) after adjustment for traditional confounders. Subgroup analysis showed that loss of POPs was more significantly linked to sarcopenia in those with advanced age (≥80years) (OR = 1.307, 95% CI = 1.116-1.532) and in females (OR = 1.165, 95%CI = 1.038-1.308). Compared to individuals with ≥5 occluding pairs of POPs, those with <5 occluding pairs of POPs had a higher incidence of sarcopenia.

CONCLUSIONS

Loss of POPs is associated with an increased risk of sarcopenia in the elderly in a Chinese population. Further research on the mechanism of the observed causal relationship is needed.

Materials in advanced design of personal protective equipment: a review

The outbreak of the Covid-19 pandemic has aroused tremendous attention toward personal protective equipment (PPE) in both scientific research and industrial manufacture. Despite decades of development in PPE design and fabrication, there's still much room for further optimization, in terms, of both protection performance and wear comfort. Interdisciplinary efforts have been devoted to this research field in recent years. Significantly, the innovation of materials, which brings about improved performance and versatile new functions for PPEs, has been widely adopted in PPE design. In this minireview, recent progress in the development of novel materials and structural designs for PPE application are presented in detail with the introduction of various material-based strategies for different PPE types, as well as the examples, which apply auxiliary components into face masks to enrich the functionalities and improve the personal feelings in the pandemic period.

Glutaredoxins regulate maize inflorescence meristem development via redox control of TGA transcriptional activity

Glutaredoxins (GRXs) are small oxidoreductases that can modify target protein activities through control of the redox (reduction/oxidation) state by reducing or glutathionylating disulfide bridges. Although CC-type GRXs are plant specific and play important roles in many processes, the mechanisms by which they modulate the activity of target proteins in vivo are unknown. In this study, we show that a maize CC-type GRX, MALE STERILE CONVERTED ANTHER1 (MSCA1), acts redundantly with two paralogues, ZmGRX2 and ZmGRX5, to modify the redox state and the activity of its putative target, the TGA transcription factor FASCIATED EAR4 (FEA4) that acts as a negative regulator of inflorescence meristem development. We used CRISPR-Cas9 to create a GRX triple knockout, resulting in severe suppression of meristem, ear and tassel growth and reduced plant height. We further show that GRXs regulate the redox state, DNA accessibility and transcriptional activities of FEA4, which acts downstream of MSCA1 and its paralogues to control inflorescence development. Our findings reveal the function of GRXs in meristem development, and also provide direct evidence for GRX-mediated redox modification of target proteins in plants.

Review of good agricultural practices for smallholder maize farmers to minimise aflatoxin contamination

Maize is consumed world-wide as staple food, livestock feed, and industrial raw material. However, it is susceptible to fungal attack and at risk of aflatoxin contamination under certain conditions. Such contamination is a serious threat to human and animal health. Ensuring that the maize used by food industry meets standards for aflatoxin levels requires significant investment across the supply chain. Good Agricultural Practices (GAP) form a critical part of a broader, integrated strategy for reduction of aflatoxin contamination. We reviewed and summarised the GAP of maize that would be effective and practicable for aflatoxin control within high-risk regions for smallholder farmers. The suggested practicable GAP for smallholder farmers were: use of drought-tolerant varieties; timely harvesting before physiological maturity; sorting to remove damaged ears and those having poor husk covering; drying properly to 13% moisture content; storage in suitable conditions to keep the crop clean and under condition with minimally proper aeration, or ideally under hermetic conditions. This information is intended to provide guidance for maize growers that will help reduce aflatoxin in high-risk regions, with a specific focus on smallholder farmers. Following the proposed guidelines would contribute to the reduction of aflatoxin contamination during pre-harvest, harvest, and post-harvest stages of the maize value chain.

P–138 When is low quality really low? Should we transfer low-grade blastocysts?

Study question

What is the live birth rate after single, low-grade blastocyst (LGB) transfer?

Summary answer

The live birth rate for LGBs is 28%, ranging between 15–31% for the different inner cell mass (ICM) and trophectoderm (TE) subgroups of LGBs.

What is known already

Live birth rates following LGB transfer are varied and have been reported to be in the range of 5–39%. However, these estimates are inaccurate as studies investigating live birth rates following LGB transfer are inherently limited by sample size (n = 10–440 for LGB transfers) due to LGBs being ranked last for transfer. Further, these studies are heterogenous with varied LGB definitions and design. Collating LGB live birth data from multiple clinics is warranted to obtain sufficient numbers of LGB transfers to establish reliable live birth rates, and to allow for delineation of different LGB subgroups, including blastocyst age and female age.

Study design, size, duration

We performed a multicentre, multinational retrospective cohort study in 9 IVF centres in China and New Zealand from 2012 to 2019. We studied the outcome of 6966 single blastocyst transfer cycles on days 5–7 (fresh and frozen) according to blastocyst grade, including 875 transfers from LGBs (&lt;3bb, this being the threshold typically applied to LGB studies). Blastocysts with expansion stage 1 or 2 (early blastocysts) were excluded.

Participants/materials, setting, methods

The main outcome measured was live birth rate. Blastocysts were grouped according to quality grade: good-grade blastocysts (GGBs; n = 3849, aa, ab and ba), moderate-grade blastocysts (MGBs; n = 2242, bb) and LGBs (n = 875, ac, ca, bc, cb and cc) and live birth rates compared using the Pearson Chi-squared test. A logistic regression analysis explored the relationship between blastocyst grade and live birth after adjustment for the confounders: clinic, female age, expansion stage, and blastocyst age.

Main results and the role of chance

The live birth rates for GGBs, MGBs and LGBs were 45%, 36% and 28% respectively (p &lt; 0.0001). Within the LGB group, the highest live birth rates were for grade c TE (30%) and the lowest were for grade c ICM (19%). The lowest combined grade (cc) maintained a 15% live birth rate (n = 7/48). After accounting for confounding factors, including female age and blastocyst characteristics, the odds of live birth were 2.33 (95% CI = 1.88–2.89) for GGBs compared to LGBs and 1.56 (95% CI = 1.28–1.92) for MGBs compared to LGBs following fresh and frozen blastocyst transfers (p &lt; 0.0001, odds ratios confirmed in exclusively frozen blastocyst transfer cycles). When stratified by individual ICM and TE grade, the odds of live birth according to ICM grade were 1.31 (a versus b; 95% CI = 1.15–1.48), 2.82 (a versus c; 95% CI = 1.91–4.18) and 2.16 (b versus c; 95% CI = 1.48–3.16; all p &lt; 0.0001). The odds of live birth according to TE grade were 1.33 (a versus b; 95% CI = 1.17–1.50, p &lt; 0.0001), 1.85 (a versus c; 95% CI = 1.45–2.34, p &lt; 0.0001) and 1.39 (b versus c; 95% CI = 1.12–1.73, p = 0.0024).

Limitations, reasons for caution

Despite the large multicentre design of the study, analyses of transfers occurring within the smallest subsets of the LGB group were limited by sample size. The study was not randomised and had a retrospective character.

Wider implications of the findings: LGBs maintain satisfactory live birth rates (averaging 28%) in the general IVF population. Even those in the lowest grading tier maintain modest live birth rates (15%; cc). It is recommended that LGBs not be universally discarded, and instead considered for subsequent frozen embryo transfer to maximize cumulative live birth rates.

Trial registration number

Not applicable

P–194 Impact of cryopreservation duration on pregnancy outcomes of vitrified-warmed blastocysts transfer using an open-device system

Study question

Is there a negative effect of long-term cryopreservation upon pregnancy outcomes after transfer of vitrified-warmed blastocysts stored in an open-device system?

Summary answer

Prolonged cryopreservation of vitrified blastocysts up to 24 months increased the incidences of clinical pregnancy, ongoing pregnancy, and live birth, while decreased early miscarriage rate.

What is known already

Vitrification is adopted as the dominant approach for cryopreservation of human oocytes and embryos. However, little is known about the potential effect of prolonged storage after vitrification on the genomic integrity and metabolism of embryos. Several studies have sought to decipher the effect of cryopreservation duration on IVF pregnancy outcomes, but few were confined to vitrification and the results were inconsistent.

Study design, size, duration

This retrospective study included 6722 patients undergoing their first vitrified-warmed blastocyst transfer (VBT) cycles from January 2015 to June 2019 in a single fertility center in South China. The study was approved by the hospital’s Ethics Committee.

Participants/materials, setting, methods

A total of 6722 eligible patients were divided into five groups according to the storage duration after vitrification: Group I: 0–3 months; Group II: 3–6 months; Group III: 6–12 months; Group IV: 12–24 months; Group V: 24–36 months. The IVF pregnancy outcomes were compared between groups. Multivariate logistic regression was conducted to evaluate the independent effect of storage duration on pregnancy outcomes.

Main results and the role of chance

The odds of clinical pregnancy outcomes were similar from Group 1 to 4. However, the chance of clinical pregnancy (Group 1 as reference; Group 2: adjusted odds ratio (aOR)= 1.04, 95% CI 0.93–1.17; Group 3: aOR = 1.02, 95% CI 0.84–1.25; Group 4: aOR = 0.93, 95% CI 0.66–1.31; Group 5: aOR = 0.54, 95% CI 0.38–0.76) , ongoing pregnancy (Group 2: aOR=0.99, 95% CI 0.89–1.11; Group 3: aOR = 0.94, 95% CI 0.77–1.14; Group 4: aOR = 0.87, 95% CI 0.62–1.22; Group 5: aOR = 0.41, 95% CI 0.29–0.60), and live birth rate (Group 2: aOR=1.00, 95% CI 0.89–1.12; Group 3: aOR = 0.98, 95% CI 0.81–1.19; Group 4: aOR = 0.91, 95% CI 0.65–1.27; Group 5: aOR = 0.46, 95% CI 0.32–0.66) significantly decreased, while the early miscarriage rate (Group 2: aOR=1.11, 95% CI 0.92–1.35; Group 3: aOR =1.25, 95% CI 0.92–1.70; Group 4: aOR = 1.33, 95% CI 0.77–2.31; Group 5: aOR = 2.42, 95% CI 1.36–4.31) significantly increased as the storage duration increased up to 24–36 months.

Limitations, reasons for caution

The primary limitation of this study was its retrospective nature. Besides, as all these data come from a single IVF treatment center, the results should be confirmed by a larger multicenter study.

Wider implications of the findings: Our study provides more evidence about the negative impact of long-term storage of vitrified embryos on the clinical outcome. Clinicians should adapt FET strategies based on the embryo storage duration.

Trial registration number

Not applicable

Adverse events associated with mirabegron 50mg versus placebo: A systematic review and meta-analysis

PURPOSE

The safety of mirabegron 50mg monotherapy was comprehensively assessed versus placebo for overactive bladder.

METHODS

A systematic literature search was conducted up to June, 2020 using PUBMED, EMBASE and Cochrane Library. Randomized controlled trials evaluating safety of mirabegron in overactive bladder were collected, and safety was assessed according to 15 adverse events. Adverse events were widely selected to be assessed if they could be calculated. Heterogeneity among studies was assessed by using the χ² test based on the Q and I² tests. Pooled effect sizes were calculated using fixed model if I²<50%, otherwise a random-effects model was chosen. The outcomes were nasopharyngitis, dry mouth, hypertension, constipation, headache, dyspepsia, urinary tract infection, dizziness, blurred vision, nausea, cardiovascular events, influenza, electrocardiogram QT prolonged, upper respiratory tract infection and high blood pressure.

RESULTS

In all, 10 peer-reviewed trials comprising 6135 patients were identified. Compared with placebo, mirabegron 50mg had an unfavorable safety profile resulting in nasopharyngitis (OR, 1.54[95% credible interval, 1.05-2.25]; P=0.03. No statistical difference was found between mirabegron 50mg and placebo groups in other 14 outcomes.

CONCLUSION

Mirabegron 50mg is further confirmed to be nearly as safe as placebo, expect for nasopharyngitis. Nasopharyngitis is associated with mirabegron 50mg monotherapy for patients with overactive bladder.

Wide-spectrum photodetector constructed on a centimeter-scale flexible SnSe2film using a new one-step strategy

Two-dimensional (2D) materials attached with flexible substrates enable possibilities to apply their superior properties to the rapidly increasing demand for foldable displays and wearable biosensors in the internet-of-things technology. However, previous two-step strategy to construct the flexible devices, namely first obtaining 2D materials elsewhere and then transferring them onto flexible substrates, can cause huge problems, including irreversibly undermining the device performance and limiting the material size. Here we propose a new one-step strategy (other than the liquid phase processing and low temperature synthesis methods), namely directly depositing appropriate 2D materials onto flexible substrates, which involves no transferring and can maintain the crystal quality and properties to the greatest extent. More importantly, this strategy in principle has no limit in the film size, hence removing a main obstacle for the practical use of flexible films, such as complex logic operations and large-area optoelectronic applications. Using this strategy, a centimeter-scale SnSe₂film is directly grown on polydimethylsiloxane, which is characterized as a uniform, out-of-plane oriented and semiconducting film that is robust to deformations. Based on the film, a flexible photodetector is fabricated and distinct photoresponse to a broad spectrum of light (405-830 nm) is observed, with remarkable technical parameters.