"Milk detector nano-sensor"

Transcription

1 "Milk detector nano-sensor" 1

2 Table of Contents Abstract... 3 Introduction... 3 Literature review... 5 Project description... 5 Conclusions and recommendations... 9 References

3 Abstract Approximately 2.5 percent of children younger than three years of age are allergic to milk. Allergy to milk is the response of the immune system to specific protein found in milk. A serious milk allergy causes anaphylaxis, a life-threatening reaction that can narrow the airways and block breathing. People allergic to milk should completely avoid eating dairy products. The project's goal is to make a "Milk detector nano-sensor" to imitate the sense of touch, by locating the nano-sensor on the fingers, the nano-sensor detect dairy products by touching them. The project discusses milk nano-sensor based on identification of lactose. Lactose is a disaccharide sugar derived from galactose and glucose that is found in milk. Lactose makes up around 2 8% of milk (by weight), that's why we can assume that whatever contains lactose contains the milk protein. We chose to fabricate the nanosensor via quantum dots due to of their most important property which is the ability to control their light absorbance and emission frequencies. The process of fabrication based on encapsulation within amphiphilic polymers, which selectively interact with the native trioctylphosphine oxide (TOPO) and trioctylphosphine (TOP) shell. The nano-sensor will be placed on the child`s finger at the dominant hand and will illuminate in specific color when it sense lactose. The idea is that kids younger than 3 years old eating with their hands and this why the nano-sensor will indicate to their supervisors that they ate food that contains milk and to treat them quickly, additional option is the supervisors to test the food before they handed it to the children. By sensing lactose in food, the nano-sensor can also help people that suffer from lactose intolerance. This may not be life threatening but it makes these people very uncomfortable and the sensor can help them avoid dairy outside their home. Introduction Allergy to cow s milk is the most common food allergy in infants and young children. In most cases, the reaction is mild, causing symptoms like a rash, a stuffy nose, or an upset stomach, but a serious milk allergy causes anaphylaxis, a life-threatening reaction that can narrow the airways and block breathing. This can be deadly. Quick treatment can stop a dangerous reaction [1]. Milk allergy is an overreaction of the immune system to a specific food protein existing in milk: alpha s1 casein protein [2]. Children with milk allergy must avoid 3

4 anything containing traces of milk ingredients in it, and in severe cases of allergy, even avoid smelling them. In our modern times in the developed world, food has become more than a survival need; food has become a center of most social events (weddings, dates, holidays and more). When one is eating outside his home he doesn't always know the exact ingredients of his meal, there could be dishes that contain dairy without one knowing. Even if a dish isn't supposed to contain dairy, it may contain traces of dairy above the dangerous level of allergens. Lactose and milk proteins are unique components that characterize cow and goats milk. Therefore we can detect the existents of dairy in our food by detecting the lactose. We will place a sensor on the finger to reduce the exposure, thus creating a sense of touch that detects dairy products. By doing so, people allergic to milk or supervisors of allergic children will be able to detect dairy presence in food by only touching it. By being a nanoscale sensor it can remain in the finger permanently and be always available for the user In addition, the sensor will notify immediately about contact with dairy products, so in cases where young children that usually eat with their hands accidentally eat dairy food their parents or their other supervisors will be able to provide them medical treatment quickly. The sensor can also be useful to people who are not allergic to milk, but suffer from lactose intolerance. Lactose intolerance is the inability of adults to digest lactose. In this case the consuming milk or products containing milk is not dangerous but causes side effects such as diarrhea, abdominal pain, and swelling. A large percentage of the population that suffers from lactose intolerance, need to moderate their milk consumption, the Awareness to the presence of dairy foods, can help them to do so. Figure 1 -Lactose (milk sugar) 4

5 Literature review Various methods are used for the determination of lactose including titrimetry, gravimetric analysis, polarimetry, spectrophotometry, chromatography (gas, liquid and high-pressure liquid chromatography), and infrared spectroscopy [4]. However, biosensors offer a low cost, quick, and reliable alternative for the determination of lactose. Several types of lactose biosensors have been reported in literature. A biosensor is a device for the detection of ananalyte that combines a biological component with a physicochemical detector component. Mehmet Akif Ersoy University, Turkey developed lactose biosensor using surfactant doped conducting polymer [4]. A research team at Tel-Aviv University developed a sensor that is based on serial reactions of three enzymes β-galactosidase, glucose oxidase, and horseradish peroxidase immobilized on a glassy carbon electrode. The sequential enzymatic reactions increase the selectivity and sensitivity of the sensor [5]. Quantum dots have been used to detect the presence of biomolecules using intricate probe designs incorporating energy donors or acceptors. For example, quantum dots can be adapted to sense the presence of the sugar maltose by conjugating the maltose binding protein to the nanocrystal surface. Upon addition of maltose, the quencher sugar conjugate is displaced and changing the fluorescence [6]. Project description The overall design: The nano-sensor for detecting milk by lactose presence responds to a chemical parameter and converts its response into an output or signal. Figure 2 shows an example of the sensing process. Figure 2 -the sensing process. (Image credit: NR Fuller,Sayo-Art LLC) 5

6 The nano-sensor will be placed on the finger at the dominant hand by special glue or sub-injection when a part of the nano-sensor is under the skin in the way that the surface of the nano sensor will be out of the skin and ready to test anything the child touches. The sensor will alert if the child eat any dairy product. The sensor will be placed on the parents fingers as well, thus enable them examine food and decide whether it is safe for the allergic child The sensor will change color and glow in the presence of lactose and that way will indicate to the supervisors that the child needs to be under close supervision and to get the anti-allergic treatment. The sensor will also cause slight pain in the finger and thereby inform the examiners the presence of dairy in food. The suggested sensor is a chemical sensor based on nanoparticles (Quantum dots (QDs)) designed to detect the presence of the specific structure of lactose. QDs are small semiconducting particles with typical size ranging from 1 nm to 10 nm. These are artificial clusters of semiconductive atoms that have the ability to confine electron motion due to their small size. One of the most important properties of quantum dots is the ability to tune their band gap and therefore to control their light absorbance and emission frequencies. Quantum dots absorb photons of light and then re-emit longer wavelength photons for a period of time. The high controllability of quantum dot size provides very precise control over the wavelength of the re-emitted photon. Therefore the color of the light emitted from the quantum dot can be manipulated without significant cost or the use of high-end technology. Additional important aspect of these nanoparticles is the ability to modify their surfaces with a wide variety of molecular ligands (such as DNA, proteins, sugars, enzymes, and more) that can bind with high specificity to many different receptors and targets. The optical properties of QDs are highly related to their size and composition and QD color can be fitted to the sensing application and to the diagnostic requirements. The luminescence of core quantum dots can be very sensitive to the surrounding chemical environment. The quantum dots are characterized by large surface area that is useful for analytes adsorption and enables sensitive measurement as well. 6

7 Therefore, QDs are fit to sense and indicate the presence of lactose in different kinds of food. The quantum dots are adapted to sense the presence of the lactose by conjugating the lactose binding protein to the nanocrystal surface.by initially incubating the quantum dots with an energy-accepting dye that is conjugated to a sugar recognized by the receptor, an excitation of the quantum dots yields little fluorescence, as the energy is nonradiatively transferred to the dye. Upon addition of lactose, the quencher sugar conjugate is displaced, restoring fluorescence in a concentrationdependent manner. Figure 3 - Quantum dots [6] The sensor change of color will alert the user about the presence of dairy. In addition, the sensor is located in the skin where there are a lot of nerves that transmits touch sensations to the brain. The sensor can transmit the chemical recognition in to electric current or thermal energy that will cause slight physical pain and warn the user from the presence of lactose in additional way. The method for fabrication: For biological applications, robust water soluble QDs are necessary. Several strategies aimed at developing stable water dispersions of luminescent QDs have been established [6]. We chose the process based on encapsulation within amphiphilic polymers, which selectively interact with the native trioctylphosphine oxide (TOPO) and trioctylphosphine (TOP) shell. This is because: 7

8 (a) There is no direct interaction with the quantum dot surface atoms and therefore can preserve the original quantum efficiency to a highest extent. (b) The polymer s large number of hydrophobic side chains strengthens the hydrophobic interaction to form more steady structures and consequently more stable water-soluble quantum dots. (c) These amphiphilic polymers are generally commercially available with low prices that make them better materials than other molecules such as peptides and phospholipids in large-scale preparation [7]. Figure 4: QD water solubility by hydrophobic interactions [6] Forming micelle through hydrophobic interaction Phospholipids such as 1, 2- dipalmitoyl-sn-glycero-3-phosphoethanolamine-n-[methoxy(polyethylene glycol)] or 1, 2-dipalmitoyl-sn-glycero-3-phosphocholine have both hydrophobic and hydrophilic ends, as seen in figure 1. They could encapsulate quantum dots in the core by forming oil-in-water micelles through hydrophobic interaction between their hydrophobic ends and the surface ligands of the quantum dots and provide watersolubility via hydrophilic exterior ends. A more promising approach is to use long chain length amphiphilic polymers to form micelle-like structures to transfer the hydrophobic quantum dots into water [7]. Our Quantum dots sensor will be adapted to sense the presence of the sugar lactose by conjugating the lactose binding protein to the nanocrystal surface. 8

9 Conclusions and recommendations Nowadays, there is no available sensor for lactose detection which can be used by individuals in their everyday life. Current sensors are used to diagnose lactose in the food industry and are not suitable to use by milk allergic children and their parents, or lactose-intolerant people. Dairy can also be selectively detected by identifying the unique proteins that existing only in milk. This target molecule requires a different sensing method and suitable sensor design. Milk allergies can be severe and life-threatening especially when it causes internal swelling of the trachea that causes suffocation without showing external signs. The response is especially dangerous for allergic young children, who aren`t aware of the danger it is for them to eat dairy, and are too young to know how to treat their allergy. In addition, a large percentage of the population suffers from lactose intolerance, therefore eating dairy impairs their life quality and thus they also have the need to know about the presence of dairy foods. The sensor enables the detection of dairy products in food by the discovery of the milk sugar - lactose, thus allowing people to enjoy eating outside their homes despite their condition. In addition, the sensor is a precaution for parents who need to look out for their allergic children. The offered sensor is a chemical sensor based on nanoparticles (Quantum dots) that is capable to selectively detect the lactose molecule. The sensor is located on the fingers, and creates a sense of touch that detects dairy in food. Nanoparticles electronic and optical properties are used for sensing applications and for immediately double alert by changing color and causing slight physical pain. Metal nanoparticles are typically biocompatible and stable in air, therefore promise a sensing product with long shelf time as well as long life-operation time. The fabrication process is cost-effective due to the simplicity of nanoparticle synthesis. It is essential to continue the research and development of this important application. Another way to improve the detector is by adding a Wi-Fi connection to electric devices such as smart phones and when the nano-sensor detects lactose it will notify immediately. In addition, by adding to the nano-sensor the ability to vibrate strongly when it detects lactose, the parents will be able to teach the child that when the sensor on their finger vibrates, they should throw away the food they are holding. 9

10 References [1] FARE-food allergy research and educationhttps:// [2] "Goat's Milk: A Natural Alternative for Milk Sensitive Patients",16 February [3]Food intolerance Diagnostics - Food tables: lactose [4] Grsoy_et_al-2014-Journal_of_Applied_Polymer_Science.pdf [5] A Three-Cascaded-Enzymes Biosensor to Determine Lactose Concentration in Raw Milk,Tel-Aviv University,2002 [6] Nanotechnology and Nano sensors, Thechnion, prof.hossam Haick - [7] William W. Yu, Emmanuel Chang, Rebekah Drezek, Vicki L. Colvin, Watersoluble quantum dots for biomedical applications, Biochemical and Biophysical Research Communications 348 (2006)