Release date: 2015-09-02 Everyone knows that the technology giant Google officially changed its name to Alphabet. In a few days, we saw another news: Alphabet's Google Life Sciences division signed a partnership with Dexcom, the world's leading manufacturer of blood glucose meters, to work together to create a "coin-sized" blood glucose meter. Among them, Dexcom is responsible for sensor development, and Google Life Sciences is responsible for miniaturization and data processing. Wait, are we really not mistaken? Want to develop a blood glucose meter with Dexcom? So where is the Google contact lens that can measure blood sugar in the legend? ! To know that at the beginning of last year, Google contact lenses have earned enough attention. Why did Google’s life sciences department start a new blood glucose meter development project after a year and a half? Further research found that, as early as 2011, Microsoft has launched a contact lens project to detect blood sugar, and currently the co-founder of Google contact lens project Babak Parviz is a member of the Microsoft contact lens research and development team. Now when I go to search for "Microsoft Contact Lenses", most of the reports that "Google Smart Contact Lenses are not new Microsoft has already started" can not find a special report on Microsoft contact lenses. Then, whether this technology is "the star of tomorrow" or "the king of the potholes", we look down. Is there glucose in the tears? Really! The basic principle of measuring blood glucose with contact lenses is to determine the correlation between the glucose content in the tears and the glucose content in the human blood, and then indirectly calculate the blood glucose level by measuring the glucose content in the tears. So let's see first, where is the glucose in the tears coming from? As shown below, the tears are mainly (the cornea and the conjunctiva are also secreted in a small amount) secreted by the lacrimal gland located in the upper part of the eye. Normally, the tears are discharged through the tear duct at a constant speed, and are concentrated near the bridge of the nose through the entire eyeball. The corner of the eye, then through the upper and lower tear duct, into the lacrimal sac, and finally into the nasal cavity [1]. Now think about "a nose and a tear", will it make sense. However, where does the glucose in the tears come from? There is no final conclusion [2]. There is currently little evidence that glucose in the tears may come from the cornea and conjunctiva. For example, there is a GLUT-1 glucose transporter in the cornea [3], but not in the lacrimal gland and conjunctiva [4]; however, there is a sodium/glucose cotransporter SGLT-1 [5] in the conjunctiva. This transporter can be based on sodium and The glucose concentration determines the transfer and withdrawal of glucose to maintain the stability of the glucose concentration in the tears. Although the source of glucose in tears is not known at present, this does not affect the enthusiasm of scientists to study the relationship between tear glucose and blood glucose. The reason is also very simple: even if I don't know how the tear glucose comes from, as long as it is related to blood glucose, we can use it. It seems to be the truth. Next, let's take a look at whether this is the case. Why is this actually a pothole technology? Since there is indeed glucose in the tears, and some researchers have assumed that it is associated with glucose in the blood, then we first look at the glucose content in the tears. First, the amount of basic tear secretion is very small. Mishima et al. discovered in 1966 that under normal conditions, the basal secretion of tears (normal secretion without stimulation) is between 0.5-2.2 μL/min, and the average secretion is 1.2 μL/min [ 6], the daily secretion is also between 0.72-3.2mL. In general, to complete the measurement of tear glucose, at least 10 μL of tears are required to fill the measurement chamber in the contact lens. It can take at least 5-20 minutes for the lacrimal gland to secrete 10 μL of tear fluid [7]. There is a serious lag in time. Second, different test methods, sampling methods have an effect on the concentration of glucose in the tears. The graph below shows the tear concentration of healthy adult tears measured by different research teams since 1937 [2]. The measurement methods in the above figure are the same, some different. However, no matter the different methods or the same method, almost no similar concentration range can be obtained. In other words, when you use different measurement methods, sampling methods, and even choose different experimental groups, you will find that the concentration of glucose in the tears falls in a completely different range. So which measurement method should we believe? Third, because the concentration of glucose in the tears is very low, the accuracy of the miniature sensor is extremely high. Mass spectrometry (ESI-MS, mass spectrometer is mostly a few hundred kilograms or more) is considered to be a detection method with high specificity and high sensitivity, so the tears measured by ESI-MS method in the above figure Sugar concentration, recently received the true tear sugar concentration. From the above measurement concentration, the tear sugar concentration should be only a few tenths of the blood glucose concentration, or even a few thousandth. In the previous article on blood glucose meters (click to view), we have concluded that the effective measurement range for the FDA-approved minimally invasive blood glucose meter Dexcom G4 is 2.22-22.2 mmol/L. Therefore, microsensors have a long way to go to measure such low glucose concentrations in tears. Although there are a large number of studies showing that the tear concentration of diabetic patients is higher than that of healthy people [9], this difference is completely negligible compared with the difference between them and blood glucose concentration. Finally, the tear composition is more complicated and is greatly affected by the outside world. There are also some studies showing a correlation between tear concentration and blood glucose concentration [10,11,12]. However, these studies are either animal experiments, in vitro experiments, or single factor variable control experiments. It is difficult to simulate the real environment of the human eye. Although the current understanding of the amount of tear secretion is basically unchanged since the study of Mishima et al in 1966. But the source of tears has always been controversial. Traditional research has always believed that the basic tear tears are basically secreted by the lacrimal gland, and the secretion of other parts such as the conjunctiva is less [13]. However, in recent years, studies have found that conjunctival secretion accounts for 25% of the basic tears [14]. When exposed to external stimuli (emotion, foreign body, onion, yawning), the massive amount of tears (the secretion rate is about 100 times normal) is secreted by the lacrimal gland. As mentioned earlier, the concentration of glucose in different sources of tears is different (determined by the glucose transporter on the secretory organs). Therefore, studies have shown that in order to accurately measure the concentration of tear glucose, it is necessary to avoid external stimuli (such as: emotions, foreign bodies, onions, yawning). Of course, we can control the sampling time while doing research to avoid the interference of external stimuli on tears. However, under normal circumstances, the effects of emotions, foreign bodies, onions, yawning, etc. on the composition of tears are basically incapable of control. After reading the above four difficulties, you should have a basic understanding of reality. Although, some studies have established a relationship between tear sugar and blood sugar. However, these relationships are based on a series of restrictions. These relationships can't stand the test in reality. Therefore, in the current field of research on the relationship between tear sugar and blood sugar, the mainstream view is that the correlation between tear glucose concentration and blood glucose concentration is uncertain [15,16]. This is not a pothole! This alone is enough for Microsoft and Google to drink a pot! There is another important difficulty to almost forget, many people with diabetes suffer from dry eye syndrome [17]. The disease affects the amount of tear secretion and the composition of the tears. Of course, scientists do not choose such patients when doing research. So, is google contact lens a joke? Just as Google just released a contact lens project to measure blood sugar in 2014, Google claimed that “we have completed several clinical studies and the results are helping to improve our prototype†(We've completed multiple clinical research studies which are helping To refine our prototype.). However, after reviewing ClinicalTrials.gov (almost every recent clinical study will be included), Dr. Bill Quick, a US health expert, did not find a clinical study of Google's contact lens project for measuring blood glucose. Later, Bill Quick called the founder of the Google Lens Project and got the answer that “data will be released at the appropriate time†[18]. It's no wonder that Google and Dexcom worked together a few days ago. When Steve Pacelli, executive vice president of Dexcom, interviewed MobiHealthNews, he was a bit dismissive of the Google Hidden Eyeglasses project. "It's just a science project." Of course, it is not that there is no way to achieve blood glucose measurement in contact lenses, but there is no way to achieve it at the current level of research. I hope that after Google and Dexcom cooperate, Professor Babak Parviz's R&D team can send a few good articles! references [1] http://; [2] Tear glucose analysis for the noninvasive detection and monitoring of diabetes mellitus. The Ocular Surface, 2007; [3] GLUT1 glucose transporter expression in the diabetic and nondiabetic human eye. Invest Ophthalmol Vis Sci 1994; [4] Glucose transporters are abundant in cells with "occluding" junctions at the blood-eye barriers. Proc Natl Acad Sci USA 1990; [5] Immunolocalization of Na-K-ATPase, Na-K-Cl and Na-glucose cotransporters in the conjunctival epithelium. Curr Eye Res 2000; [6] Determination of tear volume and tear flow, Invest Ophthalmol 1966; [7] Noninvasive Diagnostic Devices for Diabetes through Measuring Tear Glucose. Journal of Diabetes Science and Technology, January 2011; [8] Implanted electrochemical glucose sensors for the management of diabetes. Annu. Rev. Biomed. Eng. 1999; [9] Tear glucose levels in normal people and in diabetic patients. Br J Ophthalmol. Sep 1980; [10] Measurement of Tear Glucose Levels with Amperometric Glucose Biosensor/Capillary Tube Configuration. Anal. Chem. 2011; [11] Tear glucose detection of hyperglycemia. Am J Ophthalmol. 1968; [12] The glucose content of the tear fluid in normal and diabetic subjects. Jpn J Clin Ophthalmol. 1971; [13] Clinical biochemistry of tears. Surv Ophthalmol 1981; [14] Tear dynamics model. Curr Eye Res 2007; [15] Novartis signs up for Google smart lens, Nature Biotechnology, September 2014; [16] Evaluation of Commercial Glucometer Test Strips for Potential Measurement of Glucose in Tears. Anal. Chem, January 15, 2014; [17] Dry eye in diabetic patients. Am J Ophthalmol 2005; [18]http:// Source: Singularity Network Tiamulin Fumarate,Tiamulin Swine,Tiamulin Chicken,Tiamulin For Animal Use Shandong Shengli Bioengineering Co., Ltd , https://www.shenglipharm.com