COVID-19 vaccination strategies in Africa: A scoping review of the use of mathematical models to inform policy.

OBJECTIVE: Mathematical models are vital tools to understand transmission dynamics and assess the impact of interventions to mitigate COVID-19. However, historically, their use in Africa has been limited. In this scoping review, we assess how mathematical models were used to study COVID-19 vaccination to potentially inform pandemic planning and response in Africa. METHODS: We searched six electronic databases: MEDLINE, Embase, Web of Science, Global Health, MathSciNet and Africa-Wide NiPAD, using keywords to identify articles focused on the use of mathematical modelling studies of COVID-19 vaccination in Africa that were published as of October 2022. We extracted the details on the country, author affiliation, characteristics of models, policy intent and heterogeneity factors. We assessed quality using 21-point scale criteria on model characteristics and content of the studies. RESULTS: The literature search yielded 462 articles, of which 32 were included based on the eligibility criteria. Nineteen (59%) studies had a first author affiliated with an African country. Of the 32 included studies, 30 (94%) were compartmental models. By country, most studies were about or included South Africa (n = 12, 37%), followed by Morocco (n = 6, 19%) and Ethiopia (n = 5, 16%). Most studies (n = 19, 59%) assessed the impact of increasing vaccination coverage on COVID-19 burden. Half (n = 16, 50%) had policy intent: prioritising or selecting interventions, pandemic planning and response, vaccine distribution and optimisation strategies and understanding transmission dynamics of COVID-19. Fourteen studies (44%) were of medium quality and eight (25%) were of high quality. CONCLUSIONS: While decision-makers could draw vital insights from the evidence generated from mathematical modelling to inform policy, we found that there was limited use of such models exploring vaccination impacts for COVID-19 in Africa. The disparity can be addressed by scaling up mathematical modelling training, increasing collaborative opportunities between modellers and policymakers, and increasing access to funding.

SARS-CoV-2 Transmission in Alberta, British Columbia, and Ontario, Canada, January 2020-January 2022.

We estimated COVID-19 transmission potential and case burden by variant type in Alberta, British Columbia, and Ontario, Canada, during January 23, 2020-January 27, 2022; we also estimated the effectiveness of public health interventions to reduce transmission. We estimated time-varying reproduction number (Rt) over 7-day sliding windows and nonoverlapping time-windows determined by timing of policy changes. We calculated incidence rate ratios (IRRs) for each variant and compared rates to determine differences in burden among provinces. Rt corresponding with emergence of the Delta variant increased in all 3 provinces; British Columbia had the largest increase, 43.85% (95% credible interval [CrI] 40.71%-46.84%). Across the study period, IRR was highest for Omicron (8.74 [95% CrI 8.71-8.77]) and burden highest in Alberta (IRR 1.80 [95% CrI 1.79-1.81]). Initiating public health interventions was associated with lower Rt and relaxing restrictions and emergence of new variants associated with increases in Rt.

Bowel function at preschool and early childhood age in children with long-segment Hirschsprung disease.

Bowel dysfunction has been proven to be the most typical complication of long-segment Hirschsprung disease (LSHD). Additionally, bowel dysfunction in preschool and early childhood should be properly assessed, because it may result in persistent bowel dysfunction, social issues, and depression in adolescence and adulthood. This study evaluated bowel function during preschool and early childhood in patients with LSHD. A cross-sectional bowel function score (BFS) questionnaire survey was conducted on 270 infants with short-segment Hirschsprung disease (SSHD) and LSHD who underwent pull-through (PT) between January 2014 and December 2019 at the Children's Hospital of Nanjing Medical University. One hundred ninety patients who consented to the survey were asked to complete the questionnaire and were divided into two groups: the LSHD group (n = 42) and the SSHD group (n = 148). Bowel function outcomes were assessed by using a questionnaire. The total BFS score in the LSHD group was significantly lower than that in the SSHD group (15.0 [14.0, 17.0] vs. 18.0 [16.0, 19.0], p < 0.05) and did not improve with age (p > 0.05). Independent BFS items with lower scores were discovered in LSHD than in SSHD, including the capacity to hold back defecation, feeling/reporting the urge to defecate, frequency, soiling, and accidents (all p < 0.05). After subgroup analysis of follow-up age (3-5 years, 5 ~ 7 years, and > 7 years), there was no difference between the score of ability to hold back defecation over 7 years old and feeling/reporting the urge to defecate over 5 years old (all p > 0.05). The frequency and soiling scores were lower in the LSHD group than in the SSHD group over 5 years of age (all p < 0.05). Fortunately, there was no difference in constipation scores and social problems between the LSHD and SSHD groups in every sub-follow-up group (all p > 0.05).  Conclusion: Overall, bowel function at preschool and early childhood age was poorer in LSHD than in SSHD and did not improve with age. However, the ability to hold back defecation and feeling/reporting the urge to defecate with age in LSHD may be similar to those in SSHD. Simultaneously, the frequency, soiling, and number of accidents were consistently worse in the LSHD group.  Trial registration: This study was retrospectively registered in the ClinicalTrials database.gov (NCT05461924) in August 2022. What is Known: • Bowel function in SSHD is satisfactory or near-normal, and the general consensus is that the longer the aganglionic segment, the worse the bowel function after surgery. • Bowel functional outcomes of LSHD were not defined, and the limited reports of bowel functional outcomes compared with SSHD were extensively varied. Bowel dysfunction at preschool and early childhood may lead to persistent bowel dysfunction, social problems, and depression in adolescence or adulthood. What is New: • Bowel function in preschool and early childhood in patients with LSHD has not been defined and should be thoroughly assessed in a larger group of patients with precise definitions of incontinence or soiling. • The present study was primarily designed to evaluate bowel function at preschool and early childhood age in LSHD compared with SSHD in a relatively large number of HD cases using BFS.

Elevated COVID-19 Case Rates of Government Employees, District of Columbia, 2020-2022.

OBJECTIVES: To estimate the rate ratio (RR) of reported Coronavirus Disease 2019 (COVID-19) cases among governmental employees from seven District of Columbia (D.C.) departments from March 2020 to February 2022. METHODS: Poisson regression models were used to estimate the RR by department, using D.C. residents as the reference and the person-day as the offset. The COVID-19 surveillance data and the full-time equivalent hours for each department were obtained from the D.C. governmental websites. RESULTS: Five of the seven departments had statistically significant higher COVID-19 case rates than D.C. residents. Stratified by four pandemic stages, RR of Fire and Emergency Medical Services (FEMS), Office of Unified Communication (OUC), and Metropolitan Police Department (MPD) were consistently >1: FEMS: 3.34 (95% confidence interval, CI [2.94, 3.77]), 2.39 (95% CI [2.06, 2.75]), 2.48 (95% CI [2.06, 2.95]), and 3.90 (95% CI [3.56, 4.26]), respectively; OUC: 1.47 (95% CI [0.92, 2.18]), 2.72 (95% CI [1.93, 3.69]), 1.85 (95% CI [1.09, 2.92]), and 2.18 (95% CI [1.62, 2.85]), respectively; and MPD: 2.33 (95% CI [2.11, 2.58]), 1.96 (95% CI [1.75, 2.18]), 1.52 (95% CI [1.29, 1.77]), and 1.76 (95% CI [1.60, 1.92]), respectively. CONCLUSIONS: The results suggested higher case rates for emergency responders and frontline personnel than for general population in D.C.

Late Surges in COVID-19 Cases and Varying Transmission Potential Partially Due to Public Health Policy Changes in 5 Western States, March 10, 2020, to January 10, 2021.

OBJECTIVE: This study investigates the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission potential in North Dakota, South Dakota, Montana, Wyoming, and Idaho from March 2020 through January 2021. METHODS: Time-varying reproduction numbers, R t , of a 7-d-sliding-window and of non-overlapping-windows between policy changes were estimated using the instantaneous reproduction number method. Linear regression was performed to evaluate if per-capita cumulative case-count varied across counties with different population size or density. RESULTS: The median 7-d-sliding-window R t estimates across the studied region varied between 1 and 1.25 during September through November 2020. Between November 13 and 18, R t was reduced by 14.71% (95% credible interval, CrI, [14.41%, 14.99%]) in North Dakota following a mask mandate; Idaho saw a 1.93% (95% CrI [1.87%, 1.99%]) reduction and Montana saw a 9.63% (95% CrI [9.26%, 9.98%]) reduction following the tightening of restrictions. High-population and high-density counties had higher per-capita cumulative case-count in North Dakota on June 30, August 31, October 31, and December 31, 2020. In Idaho, North Dakota, South Dakota, and Wyoming, there were positive correlations between population size and per-capita weekly incident case-count, adjusted for calendar time and social vulnerability index variables. CONCLUSIONS: R t decreased after mask mandate during the region's case-count spike suggested reduction in SARS-CoV-2 transmission.

SARS-CoV-2 Transmission Potential and Policy Changes in South Carolina, February 2020 - January 2021.

INTRODUCTION: We aimed to examine how public health policies influenced the dynamics of coronavirus disease 2019 (COVID-19) time-varying reproductive number (R t ) in South Carolina from February 26, 2020, to January 1, 2021. METHODS: COVID-19 case series (March 6, 2020, to January 10, 2021) were shifted by 9 d to approximate the infection date. We analyzed the effects of state and county policies on R t using EpiEstim. We performed linear regression to evaluate if per-capita cumulative case count varies across counties with different population size. RESULTS: R t shifted from 2-3 in March to <1 during April and May. R t rose over the summer and stayed between 1.4 and 0.7. The introduction of statewide mask mandates was associated with a decline in R t (-15.3%; 95% CrI, -13.6%, -16.8%), and school re-opening, an increase by 12.3% (95% CrI, 10.1%, 14.4%). Less densely populated counties had higher attack rates (P < 0.0001). CONCLUSIONS: The R t dynamics over time indicated that public health interventions substantially slowed COVID-19 transmission in South Carolina, while their relaxation may have promoted further transmission. Policies encouraging people to stay home, such as closing nonessential businesses, were associated with R t reduction, while policies that encouraged more movement, such as re-opening schools, were associated with R t increase.

SARS-CoV-2 transmission potential and rural-urban disease burden disparities across Alabama, Louisiana, and Mississippi, March 2020 - May 2021.

PURPOSE: To quantify and compare SARS-CoV-2 transmission potential across Alabama, Louisiana, and Mississippi and selected counties. METHODS: To determine the time-varying reproduction number Rt of SARS-CoV-2, we applied the R package EpiEstim to the time series of daily incidence of confirmed cases (mid-March 2020 - May 17, 2021) shifted backward by 9 days. Median Rt percentage change when policies changed was determined. Linear regression was performed between log10-transformed cumulative incidence and log10-transformed population size at four time points. RESULTS: Stay-at-home orders, face mask mandates, and vaccinations were associated with the most significant reductions in SARS-CoV-2 transmission in the three southern states. Rt across the three states decreased significantly by ≥20% following stay-at-home orders. We observed varying degrees of reductions in Rt across states following other policies. Rural Alabama counties experienced higher per capita cumulative cases relative to urban ones as of June 17 and October 17, 2020. Meanwhile, Louisiana and Mississippi saw the disproportionate impact of SARS-CoV-2 in rural counties compared to urban ones throughout the study period. CONCLUSION: State and county policies had an impact on local pandemic trajectories. The rural-urban disparities in case burden call for evidence-based approaches in tailoring health promotion interventions and vaccination campaigns to rural residents.

An investigation of spatial-temporal patterns and predictions of the coronavirus 2019 pandemic in Colombia, 2020-2021.

Colombia announced the first case of severe acute respiratory syndrome coronavirus 2 on March 6, 2020. Since then, the country has reported a total of 5,002,387 cases and 127,258 deaths as of October 31, 2021. The aggressive transmission dynamics of SARS-CoV-2 motivate an investigation of COVID-19 at the national and regional levels in Colombia. We utilize the case incidence and mortality data to estimate the transmission potential and generate short-term forecasts of the COVID-19 pandemic to inform the public health policies using previously validated mathematical models. The analysis is augmented by the examination of geographic heterogeneity of COVID-19 at the departmental level along with the investigation of mobility and social media trends. Overall, the national and regional reproduction numbers show sustained disease transmission during the early phase of the pandemic, exhibiting sub-exponential growth dynamics. Whereas the most recent estimates of reproduction number indicate disease containment, with Rt<1.0 as of October 31, 2021. On the forecasting front, the sub-epidemic model performs best at capturing the 30-day ahead COVID-19 trajectory compared to the Richards and generalized logistic growth model. Nevertheless, the spatial variability in the incidence rate patterns across different departments can be grouped into four distinct clusters. As the case incidence surged in July 2020, an increase in mobility patterns was also observed. On the contrary, a spike in the number of tweets indicating the stay-at-home orders was observed in November 2020 when the case incidence had already plateaued, indicating the pandemic fatigue in the country.

Spatially refined time-varying reproduction numbers of SARS-CoV-2 in Arkansas and Kentucky and their relationship to population size and public health policy, March - November 2020.

PURPOSE: To examine the time-varying reproduction number, Rt, for COVID-19 in Arkansas and Kentucky and investigate the impact of policies and preventative measures on the variability in Rt. METHODS: Arkansas and Kentucky county-level COVID-19 cumulative case count data (March 6-November 7, 2020) were obtained. Rt was estimated using the R package 'EpiEstim', by county, region (Delta, non-Delta, Appalachian, non-Appalachian), and policy measures. RESULTS: The Rt was initially high, falling below 1 in May or June depending on the region, before stabilizing around 1 in the later months. The median Rt for Arkansas and Kentucky at the end of the study were 1.15 (95% credible interval [CrI], 1.13, 1.18) and 1.10 (95% CrI, 1.08, 1.12), respectively, and remained above 1 for the non-Appalachian region. Rt decreased when facial coverings were mandated, changing by -10.64% (95% CrI, -10.60%, -10.70%) in Arkansas and -5.93% (95% CrI, -4.31%, -7.65%) in Kentucky. The trends in Rt estimates were mostly associated with the implementation and relaxation of social distancing measures. CONCLUSIONS: Arkansas and Kentucky maintained a median Rt above 1 during the entire study period. Changes in Rt estimates allow quantitative estimates of potential impact of policies such as facemask mandate.

Aiming for Zero: Reducing Transmission of Coronavirus Disease 2019 in the D.C. Department of Corrections.

BACKGROUND: Washington, District of Columbia lowered severe acute respiratory syndrome coronavirus 2 transmission in its large jail while community incidence was still high. METHODS: Coordinated clinical and operational interventions brought new cases to near zero. RESULTS: Aggressive infection control and underlying jail architecture can promote correctional coronavirus disease 2019 management. CONCLUSIONS: More intensive monitoring could help confirm that in-house transmission is truly zero.

De Novo Development of a Universal Biosensing Platform by Rapid Direct Native Protein Modification.

An innovative biosensing assay was developed for simplified, cost-effective, and sensitive detection. By rapid, direct treatment of target proteins with iron porphyrin (TPPFe) in situ, a carboxyl group of amino acid conjugates with an Fe atom of the TPPFe molecule, forming a stable protein complex. We have shown that this complex not only maintains the integrity and functions of original proteins but also acquires peroxidase activity that can turn TMB to a comparably visible signal like that in ELISA. This study is unique since such conversion is difficult to achieve with standard chemical modification or molecular biology methods. In addition, the proposed immunoassay is superior to traditional ELISA as it eliminates an expensive and complicated cross-linking process of an enzyme-labeled antibody. From a practical point of view, we extended this assay to rapid detection of clinically relevant proteins and glucose in blood samples. The results show that this simple immunoassay provides clinical diagnosis, food safety, and environmental monitoring in an easy-to-implement manner.

Spatially Refined Time-Varying Reproduction Numbers of COVID-19 by Health District in Georgia, USA, March-December 2020.

This study quantifies the transmission potential of SARS-CoV-2 across public health districts in Georgia, USA, and tests if per capita cumulative case count varies across counties. To estimate the time-varying reproduction number, Rt of SARS-CoV-2 in Georgia and its 18 public health districts, we apply the R package 'EpiEstim' to the time series of historical daily incidence of confirmed cases, 2 March-15 December 2020. The epidemic curve is shifted backward by nine days to account for the incubation period and delay to testing. Linear regression is performed between log10-transformed per capita cumulative case count and log10-transformed population size. We observe Rt fluctuations as state and countywide policies are implemented. Policy changes are associated with increases or decreases at different time points. Rt increases, following the reopening of schools for in-person instruction in August. Evidence suggests that counties with lower population size had a higher per capita cumulative case count on June 15 (slope = -0.10, p = 0.04) and October 15 (slope = -0.05, p = 0.03), but not on August 15 (slope = -0.04, p = 0.09), nor December 15 (slope = -0.02, p = 0.41). We found extensive community transmission of SARS-CoV-2 across all 18 health districts in Georgia with median 7-day-sliding window Rt estimates between 1 and 1.4 after March 2020.

Intelligent Rehabilitation Assistance Tools for Distal Radius Fracture: A Systematic Review Based on Literatures and Mobile Application Stores.

OBJECTIVE: To systematically analyze the existing intelligent rehabilitation mobile applications (APPs) related to distal radius fracture (DRF) and evaluate their features and characteristics, so as to help doctors and patients to make evidence-based choice for appropriate intelligent-assisted rehabilitation. METHODS: Literatures which in regard to the intelligent rehabilitation tools of DRF were systematic retrieved from the PubMed, the Cochrane library, Wan Fang, and VIP Data. The effective APPs were systematically screened out through the APP markets of iOS and Android mobile platform, and the functional characteristics of different APPs were evaluated and analyzed. RESULTS: A total of 8 literatures and 31 APPs were included, which were divided into four categories: intelligent intervention, angle measurement, intelligent monitoring, and auxiliary rehabilitation games. These APPs provide support for the patients' home rehabilitation guidance and training and make up for the high cost and space limitations of traditional rehabilitation methods. The intelligent intervention category has the largest download ratio in the APP market. Angle measurement tools help DRF patients to measure the joint angle autonomously to judge the degree of rehabilitation, which is the most concentrated type of literature research. Some of the APPs and tools have obtained good clinical verification. However, due to the restrictions of cost, geographic authority, and applicable population, a large number of APPs still lack effective evidence to support popularization. CONCLUSION: Patients with DRF could draw support from different kinds of APPs in order to fulfill personal need and promote self-management. Intelligent rehabilitation APPs play a positive role in the rehabilitation of patients, but the acceptance of the utilization for intelligent rehabilitation APPs is relatively low, which might need follow-up research to address the conundrum.

Monitoring biothiols dynamics in living cells by ratiometric fluorescent gold carbon dots.

Changes in biothiols, including glutathione (GSH) and cysteine, are closely related to a variety of diseases and cellular functions. Real-time monitoring intracellular GSH and cysteine dynamics in living cells are important for understanding pathophysiological processes. In this study, a stable heterostructure of dual-emission fluorescent gold carbon dots (GCDs) consisting of carbon skeleton and gold nanoclusters was prepared, which emits strong blue fluorescence and weak yellow-orange fluorescence. The blue fluorescence of the as-prepared GCDs has no response to biothiols including GSH and cysteine, but a turn-on yellow-orange fluorescence would be appeared accompanied by the biothiols reacting with the GCDs. Ratiometric fluorescent bioimaging therefore may be established based on the unique GCDs to detect GSH and cysteine levels in living cells. Moreover, real time monitoring GSH and cysteine levels in various cell lines in living cells at different growth stages was realized. The concentration of GSH in cancer cells is higher than that of normal cells, however, the level of cysteine in normal cells is consistently higher than in cancer cells at different stages of cell growth. The fluorescent GCDs probe provides a promising tool for tracking on regulation of GSH and cysteine dynamics by physiological environments due to the capability for real-time quantitation of GSH and cysteine.

Real-Time Imaging Redox Status in Biothiols and Ferric Metabolism of Cancer Cells in Ferroptosis Based on Switched Fluorescence Response of Gold Carbon Dots.

Ferroptosis is an iron-dependent form of regulated cell death. In this study, a ratiometric fluorescent probe, gold carbon dots (GCDs) consisting of carbon skeleton and gold nanoclusters, was used for in situ imaging to monitor redox status in biothiols (glutathione and cysteine) and ferric metabolism of cancer cells in ferroptosis. The as-prepared GCDs can selectively respond to biothiols, interestingly, the fluorescence may be switched to sense ferric ions without interference by biothiols under proper conditions. The robust GCDs-probe exhibits excellent photobleaching resistance and can reversibly respond to intracellular biothiols/ferric ion with high temporal resolution. The 8 h real-time imaging of living cells was employed to track the fluctuation of biothiols, showing the change of redox status in ferroptosis. In addition, release of ferric ions in cells was monitored. The real-time imaging of depletion of biothiols and release of ferric ion in cells indicates the GCDs-probe can monitor how the ferroptosis regulates redox status in biothiols and ferric metabolism.

Serum level of long noncoding RNA B3GALT5-AS1 as a diagnostic biomarker of colorectal cancer.

Aim: Long noncoding RNA (lncRNA) B3GALT5-AS1 has been reported as a biomarker for cancer monitoring. This research aims to identify serum long noncoding RNA B3GALT5-AS1 as a new biomarker for the diagnosis of colorectal cancer (CRC) and evaluate its clinical value. Materials & methods: Serum B3GALT5-AS1 expression levels were measured by quantitative real-time PCR. Results: The level of B3GALT5-AS1 in CRC patients was significantly lower than that of healthy patients (p < 0.0001). Further exploration validated that high serum B3GALT5-AS1 level was related to tumor node metastasis (TNM) stage (p = 0.008) and histological differentiation (p = 0.027). Compared with the healthy control group, AUCROC of serum B3GALT5-AS1 in the CRC group was 0.762 with 95% CI: 0.698-0.826 (p < 0.0001). Conclusion: B3GALT5-AS1 may be served as a diagnostic marker for distinguishing CRC patients from healthy people.

Selectively monitoring glutathione in human serum and growth-associated living cells using gold nanoclusters.

Glutathione (GSH) plays a variety of vital functions in biological systems. Growth-associated change of GSH level in cells might be critical for cell survival and monitoring of GSH in living cells are of great significance for understanding the dynamic link between GSH and some diseases. In this work, chitason micelles templated gold nanoclusters (CM-Au NCs) emitting red fluorescence were prepared with a simple and rapid method, which shows interesting phenomenon of aggregation induced emission (AIE) affected by the size of the chitosan micelles. The unique CM-Au NCs can be used to develop turn-off fluorescent probe for detecting GSH in human serum and living cells based on the reverse process of AIE of CM-Au NCs, completely different from the principle of aggregation caused quenching (ACQ) effect, which can distinguish GSH from other biothiols (cysteine and homocysteine) and quantitatively detect GSH concentration of human serum in healthy people and cancer patients with high sensitivity. The practical application of fluorescent CM-Au NCs for cellular imaging and detecting GSH level indicates ultra-trace changes of GSH levels in normal and cancer cells could be monitored at different growth stages, which reveals that the levels of GSH in cancer cells was always higher than that of normal cells. Compared with commercial GSH assay kits for detection GSH in human serum and living cells, the proposed method was verified to be accuracy and precision. The results not only reflect the changes of GSH during cell growth at different stages, but also demonstrate the feasibility of reverse process of AIE of CM-Au NCs for detection GSH. This strategy would provide a platform to understand the dynamic link between GSH and disease to clarify the disease mechanism.

Facile preparation of peroxidase-like core-shell nanorods and application as platform for colorimetric determination of glucose, insulin and glucose/insulin ratio.

To obtain sensitive analytical detection methods, many unique materials have been developed and made them promising candidates for biosensing. In this study, a type of core-shell gold nanorods, GNR@Au2S/AuAgS/CuS, possessing peroxidase-like activity was prepared in a simple, facile manner. A colorimetric strategy for detection of blood glucose, insulin and differentiating type 1 and type 2 diabetes was developed based on the unique GNR@Au2S/AuAgS/CuS. The sensitive colorimetric approach for detection of glucose in the dynamic range of 2.5-200 µM was first established based on the catalytic performance of GNR@Au2S/AuAgS/CuS. Meanwhile, the catalytic activity of the peroxidase-like GNR@Au2S/AuAgS/CuS can be regulated by introducing the high affinity and specific reaction between DNA aptamer and insulin on the surface of GNR@Au2S/AuAgS/CuS, which allows the colorimetric assay to be extended to the detection of insulin, and a quantitative analysis of insulin based on the specific recognition can be implemented at the range from 0.014 to 1.08 µU/mL. Furthermore, colorimetric approach coupling peroxidase-like performance and specific recognition on the surface of GNR@Au2S/AuAgS/CuS nanoparticles was developed to measure glucose/insulin ratio and directly differentiate type 1 and type 2 diabetes mellitus. Practical human serum samples were tested and only the glucose/insulin ratio greater than 2.2 (µU/mL) may lead to the appearance of color change. The coupling of this different bioassay on the same nanoparticles reflects the versatility and integration characteristics of the colorimetric assay and is highly promising for improving diabetes management.

Antibacterial activities and preservative effect of chitosan oligosaccharide Maillard reaction products on Penaeus vannamei.

The purpose of this study was to understand the influence of Maillard reaction (MR) on bioactivity of chitosan oligosaccharide (COS). The antibacterial activity against Pseudomonas aeruginosa and Vibrio parahaemolyticus and preservative effect of two kinds of COS MR products (MRPs) on Penaeus vannamei were evaluated. The structures of CG (MRPs of COS and glucose) and CM (MRPs of COS and maltose) were characterized by FT-IR and their molecular weights were measured by gel permeation chromatography (GPC). The results showed that CG has enhanced antibacterial activity and preservative effect compared to COS by evaluating total volatile base-nitrogen (TVB-N), trimethylamine (TMA), pH, total bacterial count (TBC) and sensory evaluation. Meanwhile, CM showed decreased antibacterial activity and preservative effect compared to COS by evaluating TMA, pH and TBC. The results indicated that antibacterial activity and preservative effect of COS increased or decreased after MR. In other words, the type of reducing sugar involved in MR had a great impact on the functional properties of COS-saccharide MRPs and their application to be used as a food preservative.