Biocompatible chitosan-functionalized upconverting nanocomposites

Simultaneous integration of photon emission and biocompatibility into nanoparticles is an interesting strategy to develop applications of advanced optical materials. In this work, we present the synthesis of biocompatible optical nanocomposites from the combination of near-infrared luminescent lanthanide nanoparticles and water-soluble chitosan. NaYF4:Yb,Er upconverting nanocrystal guests and water-soluble chitosan hosts are prepared and integrated together into biofunctional optical composites. The control of aqueous dissolution, gelation, assembly, and drying of NaYF4:Yb,Er nanocolloids and chitosan liquids allowed us to design novel optical structures of spongelike aerogels and beadlike microspheres. Well-defined shape and near-infrared response lead upconverting nanocrystals to serve as photon converters to couple with plasmonic gold (Au) nanoparticles. Biocompatible chitosan-stabilized Au/NaYF4:Yb,Er nanocomposites are prepared to show their potential use in biomedicine as we find them exhibiting a half-maximal effective concentration (EC50) of 0.58 mg mL–1 for chitosan-stabilized Au/NaYF4:Yb,Er nanorods versus 0.24 mg mL–1 for chitosan-stabilized NaYF4:Yb,Er after 24 h. As a result of their low cytotoxicity and upconverting response, these novel materials hold promise to be interesting for biomedicine, analytical sensing, and other applications

Research on marine environment and coral distribution on Nam Yet island using VNRedsat-1 and QuickBird images

Based on the processing of VNRedsat-1 and QuickBird images in the area of Truong Sa archipelago, the research results showed the efficiency of assessing marine environmental characteristics in surroundings of these islands. In this paper, we presented the research results on Nam Yet island and adjacent area. The marine parameters in this research include sea surface temperature (SST) and chlorophyll-a concentration in the surface layer as well as in the deep layers of 20m and 40m, the distributions of the ground objects such as coral shelf, sand accumulation, coral reef combined with seagrass and seaweed. The accuracy of assessment of supervised and unsupervised classified results is approximate of 87.8%. The research results allowed assessing the environmental characteristics, warning of the risk of erosion and coastal line change in the study area

Microbial community management in aquaculture

Microbial community management in aquaculture creates benefits at the nutritional as well as at health level for cultured species. In addition, in case of biofloc application, it allows to link species at different trophic levels, making bioflocs the potential link in integrated multispecies aquaculture

Implementing aquaculture technology and innovation platforms in Asia

First paragraph: Aquaculture has emerged as one of the fastest growing agri-food systems, playing an increasingly important role in global nutrition security and contributing economic welfare to rural and coastal regions (Beveridge et al., 2013; Béné et al., 2016). At the same time the sector in globally important regions of the world like Southeast Asia remains vulnerable to a range of production risks, related to farming conditions, disease, processing and trade issues related to environmental and social sustainability (Little et al., 2016, 2018; Ahmed and Thompson, 2019; Bush et al., 2019). For the aquaculture sector to maintain its important role as a globally important sector, continual innovation of farming systems and sector level systems of response to key issues like disease are therefore required (Lebel et al., 2010; Asche and Smith, 2018; Joffre et al., 2018)

Application of satellite images and VNREDSAT-1 images in study on marine environment in Truong Sa region

The remote sensing images, including images of MODIS, VNREDSAT-1 and altimeter, are applied for researching marine environment with the different resolutions. On the basis of different time remote sensing images, we concentrated on the assessment of several characteristics including the SST, chlorophyll-a concentration and sea surface current at the different depths in different monsoons as well. With the large areas, we used the images of MODIS and altimeter. The detailed research area focuses on the Nam Yet island, and the images of VNREDSAT-1 are used. The analysis method of environmental parameters of SST and chlorophyll-a used the regression functions based on the single and combined bands to enhance the accuracy of the analysis result. The marine parameters collected at different depths in the latest field surveys on Truong Sa archipelago in the years of 2015 and 2018 are presented in this paper. On the basis of these parameters, we can analyse the relationships and compare the real field survey data and corresponding results interpreted from remote sensing images

Spatiotemporal evolution of SARS-CoV-2 Alpha and Delta variants during large nationwide outbreak of COVID-19, Vietnam, 2021

We analyzed 1,303 SARS-CoV-2 whole-genome sequences from Vietnam, and found the Alpha and Delta variants were responsible for a large nationwide outbreak of COVID-19 in 2021. The Delta variant was confined to the AY.57 lineage and caused >1.7 million infections and >32,000 deaths. Viral transmission was strongly affected by nonpharmaceutical interventions

Optimization of hatchery protocols for Macrobrachium rosenbergii culture in Vietnam

The giant freshwater prawn is commercially one of the most important crustaceans, being widely fished and reared in ponds and rice fields throughout its natural distribution and beyond. Freshwater prawn farming can be conducted by unskilled rural people on small establishments and prawns are consumed domestically by all social classes. It is an activity that can play a role in poverty reduction and the empowerment of women. It has aided in increasing job opportunities for women and increasing their contribution to household income in developing countries. However, a major constraint in the large scale aquaculture of this species is the adequate supply of seed at required quantities and in all locations where the majority of seed used in grow out farming comes from hatcheries. Existing hatcheries are not producing up to their installed capacity due to various constraints. Availability of healthy and high–quality seedlings has always been a major obstacle in the expansion of M. rosenbergii culture. The low yield because of mass mortality of hatchery–reared seed may be caued by several factors such as broodstock management, larviculture zootechniques, microbial control,… Therefore, the current study investigated several factors which affect larval performance in terms of survival and larval quality in order to improve larviculture production and optimize the efficiency of larval rearing. A first study investigated performance of M. rosenbergii broodstock from different sources. The broodstock origin had significant effects on the offspring quality. Larval quality of Chinese and Vietnamese pond–reared breeders was markedly better than that of Vietnamese wild and Hawaiian pond–reared animals in terms of larval development rate, survival and ammonia tolerance. For prawn larval rearing techniques, the best initial larval stocking density was 100–150 l–1 when using a constant–water volume, while this could be increased up to 400 l–1 in case a rearing method with increasing water volume is used. A feeding frequency of 6 times per day by first–stage Artemia nauplii proved better than feeding only twice daily. Wet or dry artificial diets can replace 25% of the Artemia nauplii ration from larval stage V onwards. Subsequently, this could be increased up to 50% from stage IX, without any negative effects on growth, survival and quality of the prawn larvae compared to a live food control. The use of enrichment cultures (ECs) of N–acyl homoserine lactone (AHL)–degrading microbial communities proved a promising tool to control potential pathogens in prawn larviculture. The addition of ECs into the larval rearing water and via enriched Artemia nauplii used for larval feeding protected the larvae from Vibrio harveyi and/or opportunitistic bacteria and had a positive effect on larval survival and larval quality. Feeding larvae of the giant freshwater prawn with β–hydroxybutyrate (PHB)–containing Artemia nauplii significantly increased survival and growth of the larvae. It proved possible to combine delivery of PHB with bio-encapsulation of Artemia nauplii with a lipid emulsion, which is a commonly used technique in the larval rearing of many fish and crustacean species. In conclusion, several factors need to be addressed in order to optimize the larval rearing techniques of M. rosenbergii and to improve larval survival and larval quality. These include amongst others broodstock source, larval rearing zootechniques and microbial control. However, the optimization of the hatchery process should also be based on the specific conditions of the location and therefore it is not possible to draft standard protocols for all locations. The results of the present study may be applied in freshwater prawn seed production, however many remaining challenges still require further research

Quorum quenching bacteria protect Macrobrachium rosenbergii larvae from Vibrio harveyi infection

Aims: In this study, we investigated the effect of N-acyl homoserine lactone-degrading bacterial enrichment cultures (ECs) on larviculture of the giant freshwater prawn Macrobrachium rosenbergii. Methods and Results: The larval performance in terms of larval growth, larval survival, larval quality, duration of the larval rearing process and microflora levels in the rearing water as well as inside the prawn gut was investigated. The application of the EC bacteria was performed in two ways: by adding them directly into the larval rearing water and via enriched Artemia nauplii used for larval feeding. The results of the study demonstrated that both ECs that were tested had a similar positive effect on larval survival and larval quality, whereas they did not affect larval growth or the duration of the larval rearing process. Conclusions: Under normal hatchery conditions, the optimal EC densities were found to be 106 CFU ml-1 for adding into the rearing water and 5 x 108 CFU ml-1 for enrichment of Artemia nauplii used for feeding of the larvae. In the hatchery, the ECs can be grown on waste streams of Artemia hatching. Significance and Impact of the Study: Application of this kind of ECs could lead to a more sustainable aquaculture production, by replacing the use of antibiotics to control diseases