STING agonist diABZI enhances the cytotoxicity of T cell towards cancer cells

Antigen-specific T cell receptor-engineered T cell (TCR-T) based immunotherapy has proven to be an effective method to combat cancer. In recent years, cross-talk between the innate and adaptive immune systems may be requisite to optimize sustained antigen-specific immunity, and the stimulator of interferon genes (STING) is a promising therapeutic target for cancer immunotherapy. The level of expression or presentation of antigen in tumor cells affects the recognition and killing of tumor cells by TCR-T. This study aimed at investigating the potential of innate immune stimulation of T cells and engineered T cells to enhance immunotherapy for low-expression antigen cancer cells. We systematically investigated the function and mechanism of cross-talk between STING agonist diABZI and adaptive immune systems. We established NY-ESO-1 full knockout Mel526 cells for this research and found that diABZI activated STING media and TCR signaling pathways. In addition, the results of flow cytometry showed that antigens presentation from cancer cells induced by STING agonist diABZI also improved the affinity of TCR-T cells function against tumor cells in vitro and in vivo. Our findings revealed that diABZI enhanced the immunotherapy efficacy of TCR-T by activating STING media and TCR signaling pathways, improving interferon-γ expression, and increasing antigens presentation of tumor cells. This indicates that STING agonist could be used as a strategy to promote TCR-T cancer immunotherapy.

NY-ESO-1-specific T cell receptor-engineered T cells and Tranilast, a TRPV2 antagonist bivalent treatment enhances the killing of esophageal cancer: a dual-targeted cancer therapeutic route

BACKGROUND

Esophageal cancer (EC) is a global canker notorious for causing high mortality due to its relentless incidence rate, convoluted with unyielding recurrence and metastasis. However, these intricacies of EC are associated with an immoderate expression of NY-ESO-1 antigen, presenting a lifeline for adoptive T cell therapy. We hypothesized that naturally isolated higher-affinity T cell receptors (TCRs) that bind to NY-ESO-1 would allow T lymphocytes to target EC with a pronounced antitumor response efficacy. Also, targeting TRPV2, which is associated with tumorigenesis in EC, creates an avenue for dual-targeted therapy. We exploited the dual-targeting antitumor efficacy against EC.

METHODS

We isolated antigen-specific TCRs (asTCRs) from a naive library constructed with TCRs obtained from enriched cytotoxic T lymphocytes. The robustness of our asTCRs and their TCR-T cell derivatives, Tranilast (TRPV2 inhibitor), and their bivalent treatment were evaluated with prospective cross-reactive human-peptide variants and tumor cells.

RESULTS

Our study demonstrated that our naive unenhanced asTCRs and their TCR-Ts perpetuated their cognate HLA-A*02:01/NY-ESO-1(157-165) specificity, killing varying EC cells with higher cytotoxicity compared to the known affinity-enhanced TCR (TCRe) and its wild-type (TCR0) which targets the same NY-ESO-1 antigen. Furthermore, the TCR-Ts and Tranilast bivalent treatment showed superior EC killing compared to any of their monovalent treatments of either TCR-T or Tranilast.

CONCLUSION

Our findings suggest that dual-targeted immunotherapy may have a superior antitumor effect. Our study presents a technique to evolve novel, robust, timely therapeutic strategies and interventions for EC and other malignancies.

HIF-1α promotes kidney organoid vascularization and applications in disease modeling

BACKGROUND

Kidney organoids derived from human pluripotent stem cells (HiPSCs) hold huge applications for drug screening, disease modeling, and cell transplanting therapy. However, these applications are limited since kidney organoid cannot maintain complete morphology and function like human kidney. Kidney organoids are not well differentiated since the core of the organoid lacked oxygen, nutrition, and vasculature, which creates essential niches. Hypoxia-inducible factor-1 α (HIF-1α) serves as a critical regulator in vascularization and cell survival under hypoxia environment. Less is known about the role of HIF-1α in kidney organoids in this regard. This study tried to investigate the effect of HIF-1α in kidney organoid vascularization and related disease modeling.

METHODS

For the vascularization study, kidney organoids were generated from human induced pluripotent stem cells. We overexpressed HIF-1α via plasmid transfection or treated DMOG (Dimethyloxallyl Glycine, an agent for HIF-1α stabilization and accumulation) in kidney progenitor cells to detect the endothelium. For the disease modeling study, we treated kidney organoid with cisplatin under hypoxia environment, with additional HIF-1α transfection.

RESULT

HIF-1α overexpression elicited kidney organoid vascularization. The endothelial cells and angiotool analysis parameters were increased in HIF-1α plasmid-transfected and DMOG-treated organoids. These angiogenesis processes were partially blocked by VEGFR inhibitors, semaxanib or axitinib. Cisplatin-induced kidney injury (Cleaved caspase 3) was protected by HIF-1α through the upregulation of CD31 and SOD2.

CONCLUSION

We demonstrated that HIF-1α elicited the process of kidney organoid vascularization and protected against cisplatin-induced kidney organoid injury in hypoxia environment.

SYVN1 ubiquitinates FoxO1 to induce β-catenin nuclear translocation, PD-L1-mediated metastasis, and immune evasion of hepatocellular carcinoma

BACKGROUND

A high incidence of hepatocellular carcinoma (HCC), the most frequently diagnosed form of liver cancer, is observed in Africa and Asia. SYVN1 is upregulated in HCC; however, the biological roles of SYVN1 in immune evasion remain unclear.

METHODS

RT-qPCR and western blot were employed to detect the expression levels of SYVN1 and the key molecules in HCC cells and tissues. Flow cytometry was used to determine the proportion of T cells, and an ELISA assay was used to determine the amount of IFN-γ secreted. Cell viability was monitored by CCK-8 and colony formation assays. The metastatic properties of HCC cells were detected by Transwell assays. Bioinformatics analysis, ChIP, and luciferase assays were used to study the transcriptional regulation of PD-L1. Co-IP was used to detect direct interaction between SYVN1 and FoxO1, as well as the ubiquitination of FoxO1. The in vitro findings were validated in xenograft and lung metastasis models.

RESULTS

In HCC cells and tissues, SYVN1 was upregulated while FoxO1 was downregulated. SYVN1 knockdown or FoxO1 overexpression reduced PD-L1 expression, and inhibited immune evasion, cell growth, and metastasis in HCC cells. Mechanistically, FoxO1 regulated PD-L1 transcription in a β-catenin-independent or -dependent manner. Functional studies further showed that SYVN1 promoted immune evasion, cell proliferation, migration and invasion via facilitating ubiquitin-proteasome-dependent degradation of FoxO1. In vivo investigations showed that silencing of SYVN1 inhibited immune evasion and metastasis of HCC cells, possible via the FoxO1/PD-L1 axis.

CONCLUSION

SYVN1 regulates FoxO1 ubiquitination to stimulate β-catenin nuclear translocation and promotes PD-L1-mediated metastasis and immune evasion in HCC.

A Rationally Designed CRISPR/Cas12a Assay Using a Multimodal Reporter for Various Readouts

The CRISPR/Cas systems offer a programmable platform for nucleic acid detection, and CRISPR/Cas-based diagnostics (CRISPR-Dx) have demonstrated the ability to target nucleic acids with greater accuracy and flexibility. However, due to the configuration of the reporter and the underlying labeling mechanism, almost all reported CRISPR-Dx rely on a single-option readout, resulting in limitations in end-point result readouts. This is also associated with high reagent consumption and delays in diagnostic reports due to protocol differences. Herein, we report for the first time a rationally designed Cas12a-based multimodal universal reporter (CAMURE) with improved sensitivity that harnesses a dual-mode reporting system, facilitating options in end-point readouts. Through systematic configurations and optimizations, our novel universal reporter achieved a 10-fold sensitivity enhancement compared to the DETECTR reporter. Our unique and versatile reporter could be paired with various readouts, conveying the same diagnostic results. We applied our novel reporter for the detection of staphylococcal enterotoxin A due to its high implication in staphylococcal food poisoning. Integrated with loop-mediated isothermal amplification, our multimodal reporter achieved 10 CFU/mL sensitivity and excellent specificity using a real-time fluorimeter, in-tube fluorescence, and lateral flow strip readouts. We also propose, using artificially contaminated milk samples, a fast (2-5 min) Triton X-100 DNA extraction approach with a comparable yield to the commercial extraction kit. Our CAMURE could be leveraged to detect all gene-encoding SEs by simply reprogramming the guide RNA and could also be applied to the detection of other infections and disease biomarkers.

Prevalence and Correlates of Stunting among Children Aged 6-23 Months from Poor Households in Rwanda

Stunted linear growth continues to be a public health problem that overwhelms the entire world and, particularly, developing countries. Despite several interventions designed and implemented to reduce stunting, the rate of 33.1% is still high for the proposed target of 19% in 2024. This study investigated the prevalence and associated factors of stunting among children aged 6-23 months from poor households in Rwanda. A cross-sectional study was conducted among 817 mother-child dyads (two individuals from one home) living in low-income families in five districts with a high prevalence of stunting. Descriptive statistics were used to determine the prevalence of stunting. In addition, we used bivariate analysis and a multivariate logistic regression model to measure the strength of the association between childhood stunting and exposure variables. The prevalence of stunting was 34.1%. Children from households without a vegetable garden (AOR = 2.165, p-value < 0.01), children aged 19-23 months (AOR = 4.410, p-value = 0.01), and children aged 13-18 months (AOR = 2.788, p-value = 0.08) showed increased likelihood of stunting. On the other hand, children whose mothers were not exposed to physical violence (AOR = 0.145, p-value < 0.001), those whose fathers were working (AOR = 0.036, p-value = 0.001), those whose parents were both working (AOR = 0.208, p-value = 0.029), and children whose mothers demonstrated good hand washing practice (AOR = 0.181, p-value < 0.001) were less likely to be stunted. Our findings underscore the importance of integrating the promotion of handwashing practices, owning vegetable gardens, and intimate partner violence prevention in the interventions to fight child stunting.

Harnessing enhanced CRISPR/Cas12a trans-cleavage activity with extended reporters and reductants for early diagnosis of Helicobacter pylori, the causative agent of peptic ulcers and stomach cancer

Developing rapid and non-invasive diagnostics for Helicobacter pylori (HP) is imperative to prevent associated diseases such as stomach gastritis, ulcers, and cancers. Owing to HP strain heterogeneity, not all HP-infected individuals incur side effects. Cytotoxin-associated gene A (CagA), and vacuolating cytotoxin A (VacA) genes predominantly drive HP pathogenicity. Therefore, diagnosing CagA and VacA genotypes could alert active infection and decide suitable therapeutics. We report an enhanced LbCas12a trans-cleavage activity with extended reporters and reductants (CEXTRAR) for early detection of HP. We demonstrate that extended ssDNA reporter acts as an excellent signal amplifier, making it a potential alternative substrate for LbCas12a collateral activity. Through a systematic investigation of various buffer components, we demonstrate that reductants improve LbCas12a trans-cleavage activity. Overall, our novel reporter and optimal buffer increased the trans-cleavage activity to an order of 16-fold, achieving picomolar sensitivity (171 pM) without target pre-amplification. Integrated with loop-mediated isothermal amplification (LAMP), CEXTRAR successfully attained attomolar sensitivity for HP detection using real-time fluorescence (43 and 96 aM), in-tube fluorescence readouts (430 and 960 aM), and lateral flow (4.3 and 9.6 aM) for CagA and VacA, respectively. We also demonstrate a rapid 2-min Triton X-100 lysis for clinical sample analysis, which could provide clinicians with actionable information for rapid diagnosis. CEXTRAR could potentially spot the ¹³C urea breath test false-negatives. For the first time, our study unveils an experimental outlook to manipulate reporters and reconsider precise cysteine substitution via protein engineering for Cas variants with enhanced catalytic activities for use in diagnostics and genetic engineering.

Large-scale expansion of human umbilical cord-derived mesenchymal stem cells using PLGA@PLL scaffold

Mesenchymal stem cells (MSCs) are highly important in biomedicine and hold great potential in clinical treatment for various diseases. In recent years, the capabilities of MSCs have been under extensive investigation for practical application. Regarding therapy, the efficacy usually depends on the amount of MSCs. Nevertheless, the yield of MSCs is still limited due to the traditional cultural methods. Herein, we proposed a three-dimensional (3D) scaffold prepared using poly lactic-co-glycolic acid (PLGA) nanofiber with polylysine (PLL) grafting, to promote the growth and proliferation of MSCs derived from the human umbilical cord (hUC-MSCs). We found that the inoculated hUC-MSCs adhered efficiently to the PLGA scaffold with good affinity, fast growth rate, and good multipotency. The harvested cells were ideally distributed on the scaffold and we were able to gain a larger yield than the traditional culturing methods under the same condition. Thus, our cell seeding with a 3D scaffold could serve as a promising strategy for cell proliferation in the large-scale production of MSCs. Moreover, the simplicity and low preparation cost allow this 3D scaffold to extend its potential application beyond cell culture.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s40643-023-00635-6.

Thermal stress involved in TRPV2 promotes tumorigenesis through the pathways of HSP70/27 and PI3K/Akt/mTOR in esophageal squamous cell carcinoma

BACKGROUND

The transient receptor potential vanilloid receptor 2 (TRPV2) has been found to participate in the pathogenesis of various types of cancers, however, its role(s) in the tumorigenesis of ESCC remain poorly understood.

METHODS

Western blotting and immunohistochemistry were performed to determine the expression profiles of TRPV2 in the ESCC patient tissues. A series of in vitro and in vivo experiments were conducted to reveal the role of TRPV2 in the tumorigenesis of ESCC.

RESULTS

Our study first uncovered that the activation of TRPV2 by recurrent acute thermal stress (54 °C) or O1821 (20 μM) promoted cancerous behaviours in ESCC cells. The pro-angiogenic capacity of the ESCC cells was found to be enhanced profoundly and both tumour formation and metastasis that originated from the cells were substantially promoted in nude mouse models upon the activation of TRPV2. These effects were inhibited significantly by tranilast (120 μM) and abolished by TRPV2 knockout. Conversely, overexpression of TRPV2 could switch the cells to tumorigenesis upon activation of TRPV2. Mechanistically, the driving role of TRPV2 in the progression of ESCC is mainly regulated by the HSP70/27 and PI3K/Akt/mTOR signalling pathways.

CONCLUSIONS

We revealed that TRPV2-PI3K/Akt/mTOR is a novel and promising target for the prevention and treatment of ESCC.

Mycotoxins detection: view in the lens of molecularly imprinted polymer and nanoparticles

Molecularly imprinted polymers (MIPs) are tailor-made functional composites which selectively recognize and bind the target molecule of interest. MIP composites are products of the massively cross-linked polymer matrices, generated via polymerization, with bio-inspired recognition cavities that are morphologically similar in size, shape and spatial patterns to the target conformation. These features have enabled researchers to expand the field of molecular recognition, more specifically for target with peculiar requirements. Nevertheless, MIPs alone are characterized with weak sensitivity. Besides, nanoparticles (NPs) are remarkably sensitive but also suffer from poor selectivity. Intriguingly, the combination of the two results in a highly sensitive and selective MIP composite. For instance, the conjugation of different functional NPs with MIPs can generate new flexible target capture tools, either a dynamic sensor or a novel drug delivery system. In this regard, although the technology is considered an established and feasible approach, it is still perceived as a burgeoning technology for various fields, which makes it unceasingly worthy reviewing. Therefore, in this review, we attempt to give an update on various custom-made biosensors based on MIPs in combination with various NPs for the detection of mycotoxins, the toxic secondary metabolites of fungi. We first summarize the classification, prevalence, and toxicological characteristics of common mycotoxins. Next, we provide an overview of MIP composites and their characterization, and then segment the role of NPs with respect to common types of MIP-based sensors. At last, conclusions and outlook are discussed.

Rational Programming of Cas12a for Early-Stage Detection of COVID-19 by Lateral Flow Assay and Portable Real-Time Fluorescence Readout Facilities

Coronavirus disease 2019 (COVID-19) caused by the SARS-CoV-2 virus has led to a global pandemic with a high spread rate and pathogenicity. Thus, with limited testing solutions, it is imperative to develop early-stage diagnostics for rapid and accurate detection of SARS-CoV-2 to contain the rapid transmission of the ongoing COVID-19 pandemic. In this regard, there remains little knowledge about the integration of the CRISPR collateral cleavage mechanism in the lateral flow assay and fluorophotometer. In the current study, we demonstrate a CRISPR/Cas12a-based collateral cleavage method for COVID-19 diagnosis using the Cas12a/crRNA complex for target recognition, reverse transcription loop-mediated isothermal amplification (RT-LAMP) for sensitivity enhancement, and a novel DNA capture probe-based lateral flow strip (LFS) or real-time fluorescence detector as the parallel system readout facility, termed CRICOLAP. Our novel approach uses a customized reporter that hybridizes an optimized complementary capture probe fixed at the test line for naked-eye result readout. The CRICOLAP system achieved ultra-sensitivity of 1 copy/µL in ~32 min by portable real-time fluorescence detection and ~60 min by LFS. Furthermore, CRICOLAP validation using 60 clinical nasopharyngeal samples previously verified with a commercial RT-PCR kit showed 97.5% and 100% sensitivity for S and N genes, respectively, and 100% specificity for both genes of SARS-CoV-2. CRICOLAP advances the CRISPR/Cas12a collateral cleavage result readout in the lateral flow assay and fluorophotometer, and it can be an alternative method for the decentralized field-deployable diagnosis of COVID-19 in remote and limited-resource locations.

A rapid and sensitive CRISPR/Cas12a based lateral flow biosensor for the detection of Epstein-Barr virus

Nasopharyngeal carcinoma (NPC) is one of the most common malignant tumors in the world, and several studies have associated Epstein-Barr virus (EBV) with NPC occurrence and development. EBV-PCR (polymerase chain reaction), in situ hybridization and immunoassays are the most common methods for NPC identification. However, these approaches have drawbacks, which include tedious procedures and false results. Therefore, a rapid, accurate, and sensitive clinical diagnostic method for the prognosis of EBV-related diseases is needed. In this study, we developed a simple and sensitive approach for EBV detection based on the combination of CRISPR-Cas12a and a lateral flow biosensor (LFB). Cas12a exhibits collateral cleavage propensity of both target DNA and any single-stranded(ss) DNA in the vicinity (herein referred to as a reporter). The LFB test line contained an ssDNA probe complementary to the reporter. In the presence of the target, Cas12a trans-cleaved the ssDNA reporter, which resulted in the inability of cleaved sequences to bind the LFB test line. With a PCR pre-amplification of the target (45 min), the assay achieved a sensitivity of 7.1 × 10-14 M (∼42 000 copies per μl) both in plasmid and plasmid-spiked samples. The assay attained a high specificity in the presence of various bacteria and applicability in EBV Burkitt's lymphoma serum samples. This method could be applied for the detection of EBV and other infectious diseases.

Generation of UCiPSC-derived neurospheres for cell therapy and its application

BACKGROUND

Neural stem cell (NSC) therapy remains one of the most potential approaches for the treatment of neurological disorders. The discovery of human induced pluripotent stem cells (hiPSCs) and the establishment of hiPSC-derived human neural stem cells (hiNSCs) have revolutionized the technique of cell therapy. Meanwhile, it is often required that NSCs are stored and transported to a long distance for research or treatment purposes. Although high survival rates could be maintained, conventional methods for cell transportation (dry ice or liquid nitrogen) are inconvenient and expensive. Therefore, the establishment of a safe, affordable, and low-cost strategy to store and transport easily accessible hiPSCs and hiNSCs, with characteristics that match fetal hNSCs, is incredibly urgent.

METHODS

We reprogrammed human urinary cells to iPSCs using a non-integrating, virus-free technique and differentiated the iPSCs toward iNSCs/neurospheres and neurons, under Good Manufacturing Practice (GMP)-compatible conditions. The pluripotency of iPSCs and iNSCs was characterized by a series of classical methods (surface markers, karyotype analysis, and in vitro as well as in vivo differentiation capabilities, etc.).

RESULTS

Here, our results showed that we successfully generated hiNSCs/neurospheres from more available, non-invasive, and more acceptable urinary cells by a virus-free technique. Next, we demonstrated that the iNSCs differentiated into mature cerebral cortical neurons and neural networks. Interestingly, hiNSCs survived longer as neurospheres at ambient temperature (AT) than those cultured in a monolayer. Within 7 days approximately, the neural viability remained at > 80%, while hiNSCs cultured in a monolayer died almost immediately. Neurospheres exposed to AT that were placed under standard culture conditions (37 °C, 5% CO₂) recovered their typical morphology, and retained their proliferation and differentiation abilities.

CONCLUSIONS

In this study, we provided a simple method for the storage of NSCs as neurospheres at AT as an alternative method to more costly and inconvenient traditional methods of cryopreservation. This will enable hiNSCs to be transported over long distances at AT and facilitate the therapeutic application of NSCs as neurospheres without any further treatment.

Ultrasensitive Fluorometric Angling Determination of Staphylococcus aureus in Vitro and Fluorescence Imaging in Vivo Using Carbon Dots with Full-Color Emission

Rapid, accurate, and safe screening of foodborne pathogenic bacteria is essential to effectively control and prevent outbreaks of foodborne illness. Fluorescent sensors constructed from carbon dots (CDs) and nanomaterial-based quenchers have provided an innovative method for screening of pathogenic bacteria. Herein, an ultrasensitive magnetic fluorescence aptasensor was designed for separation and detection of Staphylococcus aureus (S. aureus). Multicolor fluorescent CDs with a long fluorescent lifetime (6.73 ns) and high fluorescence stability were synthesized using a facile hydrothermal approach and modified cDNA as a highly sensitive fluorescent probe. CD fluorescence was quenched by Fe₃O₄ + aptamer via fluorescence resonance energy transfer (FRET). Under optimal conditions, the FRET-based aptasensor can detect S. aureus accompanied by a wide linear range of 50-10⁷ CFU·mL^-1 and a detection limit of 8 CFU·mL^-1. Compared with other standard methods, this method was faster and more convenient, and the entire test was finished within 30 min. The capability of the aptasensor was simultaneously investigated on food samples. Additionally, the developed CDs exhibited excellent biocompatibility and were thus applied as fluorescent probes for bioimaging both in vitro and in vivo. This new platform provided an excellent application of the CDs for detecting and bioimaging pathogenic bacteria.

Cell Based-Green Fluorescent Biosensor Using Cytotoxic Pathway for Bacterial Lipopolysaccharide Recognition

Lipopolysaccharide (LPS), a characteristic component of the outer membrane of Gram-negative bacteria, can be used as an effective biomarker to detect bacterial contamination. Here, we reported a 293/hTLR4A-MD2-CD14 cell-based fluorescent biosensor to detect and identify LPS, which is carried out in a 96-well microplate which is nondestructive, user-friendly, and highly efficient. The promoter sequence of the critical signaling pathway gene ZC3H12A (encoding MCPIP1 protein) and enhanced green fluorescence protein (EGFP) were combined to construct a recombinant plasmid, which was transferred into 293/hTLR4A-MD2-CD14 cells through lipid-mediated, DNA-transfection way. LPS was able to bind to TLR4 and coreceptors-induced signaling pathway could result in green fluorescent protein expression. Results show that stable transfected 293/hTLR4A-MD2-CD14 cells with LPS treatment could be directly and continually observed under a high content screening imaging system. The novel cell-based biosensor detects LPS at low concentration, along with the detection limit of 0.075 μg/mL. The cell-based biosensor was evaluated by differentiating Gram-negative and Gram-positive bacteria and detecting LPS in fruit juices as well. This proposed fluorescent biosensor has potential in sensing LPS optically in foodstuff and biological products, as well as bacteria identification, contributing to the control of foodborne diseases and ensurance of public food safety with its high throughput detection way.

Sensory Characteristics of Maillard Reaction Products Obtained from Sunflower Protein Hydrolysates and Different Sugar Types

The effect of different sugar types on the sensory characteristics of Maillard reaction products (MRPs) obtained from sunflower protein hydrolysates was evaluated. MRPs were prepared at 120 °C for a time of 2 h and a pH of 7.4. Results showed that the browning intensity, colour development and free and total amino acids of MRPs were highly affected by the sugar types. Peptide-xylose-cysteine (PXC) were more dark-brown in colour with lower free and total amino acid (FAA and TAA) content compared to the other MRPs. However, PXC showed great mouthfulness and continuity taste with stronger meat-like flavour and umami taste compared to MRPs. MRPs from hexose except PGaC, showed acceptable mouthfulness and continuity taste while PLC and PMC and PGaC showed higher caramel-like flavour and bitter taste. Furthermore, pentose sugars (xylose) were the great precursor of sulphur-containing compounds. It could be concluded that sunflower peptides, xylose, cysteine model system could be a good precursor of flavour enhancers.

Contribution of crosslinking products in the flavour enhancer processing: the new concept of Maillard peptide in sensory characteristics of Maillard reaction systems

In this study, the flavour-enhancing properties of the Maillard reaction products (MRPs) for different systems consisted of different peptides (sunflower, SFP; corn, CP and soyabean SP) with, xylose and cysteine were investigated. Maillard systems from peptides of sunflower, corn and soyabean with xylose and cysteine were designated as PXC, MCP and MSP, respectively. The Maillard systems were prepared at pH of 7.4 using temperature of 120C for 2 h. Results showed that all systems were significantly different in all sensory attributes. The highest scores for mouthfulness and continuity were observed for MCP with the lowest peptides distribution between 1000 and 5000 Da, known as Maillard peptide. This revealed that the MCP with the lowest Maillard peptide content had the strongest "Kokumi" effect compared to the other MRPsand demonstrated that "kokumi effect" of MRPs was contributed by not only the "Maillard peptide" defined by the molecular weight (1000-5000 Da). Results on sensory evaluation after fractionation of PXC followed by enzymatic hydrolysis showed no significant differences between PXC, P-PXC and their hydrolysates. This observation therefore confirmed that the presence of other contributors attributed to the "Kokumi" effect rather than the Maillard peptide. It can be deduced that the unhydrolyzed crosslinking products might have contributed to the "Kokumi" effect of MRPs. The structures of four probable crosslinking compounds were proposed and the findings have provided new insights in the sensory characteristics of xylose, cysteine and sunflower peptide MRPs.