Team:NJMU-China/Design

Can you hear the Sound of Silence ?

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Model

Overview

Considering the many problems in ASD detection, we think it necessary to develop a better plan for families or primary medical organizations. Based on our preliminary researches, we concluded that families with suspicious autistic children are in need of a detection plan satisfies:

(1) As for the complex etiology of ASD, the plan should base not only on behavioral changes but also on genetic and metabolic alterations.

(2) As for the social-psychological factors that hinder parents, the plan should be private, convenient, and easy to approach.

(3) Overall, as a screening plan rather than a diagnostic method, it would be better if the plan has higher sensitivity.

Our Solution: Sound of Silence

Name of our project: Sound of Silence stands for our purpose. As autistic children, so-called children from stars, barely interact with others let alone tending someone for help, we want to ‘speak’ for them through this detection plan.

Part A: SOS, The Test Strip

1. Selection of Biomarker: Serotonin

As stated before, we would like to find a biomarker that represents both genetic and metabolic changes in ASD development to improve sensitivity by covering most aspects of its causes and pathological processes.

During background learning, we found that besides main symptoms like altered social communication and stereotyped behaviors, ASD most commonly associates with medical comorbidities and gastrointestinal (GI) dysfunction^1,2. Studies have demonstrated a correlation between GI dysfunction and the degree of social impairment in ASD³, suggesting that overlapping developmental defects in the brain and the intestine and/or a defect in communication between the enteric and central nervous systems (ENS and CNS, respectively), known as the gut-brain axis, could be responsible for the observed phenotypes ^4,5. This reminds us of a key neurotransmitter, serotonin.

Serotonin, or 5-hydroxytryptamine(5-HT), as a critical modulator of ENS and CNS development and function, could be a nexus for the gut-brain axis in ASD. As a critical modulator of cortical function, serotonin's metabolism is defective in ASD brain^6,7. Also, the gain of function rare-variants (17q11.2 region) in Slc6a4, the gene which encodes SERT, in individuals with ASD, has been found to cause hyperserotonemia ^8,9. The most common of these variants, SERT Ala56, was found to be associated with both rigid-compulsive behavior and sensory aversion¹⁰.

According to the literature we mentioned above, the clinical correlates between hyperserotonemia and ASD-associated behaviors (e.g. stereotypy and self-injury) have been consistent. Therefore, it's reasonable to consider targeting serotonin as the biomarker in ASD detection and even the long-term surveillance of behavior changes.

2. Detecting Urine Instead of Blood

Considering privacy and convenience, we aim to design a domestic test method. Though there exist various methods and equipment for domestic blood tests like home blood glucose meter, we decided to avoid any operations that will increase the risk of infection, especially under this circumstance, the pandemic of COVID-19.

As the main route of serotonin’s excretion, elevated urinary serotonin levels have been found in research ^11,12. Also, we plan to complete our sample collection process before November and began our independent verification using HPLC/MS as a golden standard.

3. Design of Biosensor: Bases on Quorum-Sensing System

We found that there exist no designed biosensors against serotonin. Therefore, we decided to start a de novo design the biosensor of serotonin.

First, through massive literature investigation, we found that serotonin acts as an interkingdom signaling molecule via quorum sensing and stimulates the production of bacterial virulence factors as well as increases biofilm formation in vitro and in vivo in a novel mouse infection model ¹³. Specifically, no response was noted in the rhl cellular system, indicating specificity for the las QS pathway.

Therefore, it is reasonable for us to design the biosensor with QS regulatory system as recognition elements and β-galactosidase as the reporter protein, which could show a visible color change in the presence of X-gal (Substrate).

4. Design of Device: A Test Strip

Our team peruses more than operative convenience, but also portability and economic availability. After discussion we came up with our preliminary plan: slices of block-shaped LB medium with E. coli embedded. However, considering our proposed scene of usage, at home, it could bring various problems in storage such as contaminations of containers (e.g. household refrigerator).

During further literature research, we found research that coincidently match our design ¹⁴. They reported a filter-paper-based strip biosensor for the detection of bacterial quorum sensing signaling molecules, N-acylhomoserine lactones (AHLs) in saliva. Being body fluid like saliva, we consider it appropriate to adapt this device to target urine in our project.

To make the adaptation, we refer to mathematic modeling and completed preliminary optimization of this test strip.

Part B: SOS+, The Parallel Screening Strategy

ASD is well recognized to be biologically heterogeneous where various factors are associated, including genetic, metabolic, and environmental ones ¹⁵. Also, patients show different changes in different metabolites, as they have their distinct altered metabolic pathways. Therefore, targeting only one metabolite, for example, serotonin, in the detection, would compromise the sensitivity as subjects could have developed ASD based on other metabolic disorders such as lysine metabolism ¹².

As for the SOS+, we employed a machine learning algorithm and find a combination of metabolites for screening that performs best by representing most of the heterogeneous patient population. As for the output metabolites list, we would further discover according to biosensors in a high-throughput way based on systems-level Escherichia coli genome library construction and screening. The systematic biosensor design was referred to a published pipeline that utilizes next-generation sequencing and computational analysis ¹⁶.

Part C: Integrated Human Practices

Even though ASD can be diagnosed as early as 6 months, the average age of detection in the USA is as late as 4.5 years old 8 ¹⁷. Currently, most researches focused on the complicated etiology of ASD, the identification of biomarkers at omics-level or diagnosis by imaging ^18-20, and our project focused on improvements of early detection through experiments and modeling as well.

“It is far more important to know what person the disease has than what disease the person has.”

― Hippocrates

We believe, it is of great importance to meet with these autistic children. Therefore, we planned to visit Haizhixing Autism Children Rehabilitation Center in Jiangning District, Nanjing to accomplish voluntary work and consult related professionals about our project design. During this activity, we found that there exist various social-psychological factors hindering early detection besides those that are technological.

To further identify and understanding these factors, we would like to resort to social medical qualitative research methods that are the most suitable for this approach because of their emphasis on people’s lived experience ²¹. They are considered to be well suited for locating the meanings that people place on the events, processes, and structures of their lives and their perceptions, presuppositions and assumptions ²². With structured or semi-structured interviews, we would be able to investigate the whole process from suspecting children of autistic symptoms to deciding to seek professional medical help.

Besides, we found that parents or even staffs in special education agents lack knowledge of food intake cautions concerning autistic children. Therefore, it would be of public benefit to conducting related educations.

In all, through our integrated human practices including interviews, social medicine researches and health education, we would like to close the gap with the community from all aspects.

References

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