Biosensor Designed to Detect HIV Within One Week of Infection

A biosensor has been designed by scientists from The Spanish National Research Council (Consejo Superior de Investigaciones Científicas (in Spanish- CSIC) that can be used to detect HIV infection after a week of infection. The sensor consists of mechanical silicon structures with nanoparticles of gold with p24 present between the micromechanical silicon structures and the gold nanoparticles. The study titled “Ultrasensitive detection of HIV-1 p24 antigen by a hybrid nanomechanical-optoplasmonic platform with potential for detecting HIV-1 at first week after infection” was published in PLOS recently.

Apart from being able to detect the infection within a week, the test takes only 4 hours and 45 minutes that allows the results to be provided the same day.

Structure of the Biosensor

In the structure of the biosensor, the gold nanoparticles contain plasmons which are optical resonances. These plasmons can scatter light, a factor that has resulted in bringing attention to these structures in the field of optics. The micromechanical structures detect small intermolecular forces which makes them efficient. 

When these two structures are combines, they produce both optical signals as well as mechanical structures, resulting in remarkable sensitivity and ability to detect p24. A patented technology, it is already being used to detect some forms of cancer.

Dr. Javier Tamayo, a CSIC researcher, said that the physical aspect of the chip used in this study is identical to the one used in biomarker studies. However, the chemical aspect of the chip like the solutions used would vary depending upon what is being detected.  The research team involved in the study is trying to identify other possible applications of this biosensor.

Key Facts About Structure of the Biosensor

The biosensor

• Uses microelectronics technology that are well established
• Has lowered production cost
• Is simple to use
• Is ideal for use in developing nations

Functioning of the Biosensor

• One millilitre of human serum was added onto the biosensor for a period of one hour at 37 °C.
• This is carried out to facilitate binding of any existing HIV-1 p24 antigens to antibodies that are present on the surface of the sensor.
• The biosensor is re-incubated for 15 minutes at 37 °C with gold nanoparticles. This will allow identification of the p24 proteins.
• The unbound particles are removed by rinsing.

The total time taken for the test is 4 hours and 45 minutes which, according to Dr. Javier, will allow the test to be repeated the same day. The results of the study were found to be statistically significant which makes it eligible for use in medical services.

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Detecting HIV

Seroconversion is the time taken for the HIV virus to result in the detectable presence of antibodies in the blood of the infected individual. Currently, HIV is detected by

• Using the Nucleic Acid Amplification Tests (NAAT) which identifies the presence of viral RNA in the blood. This method can detect 20-35 copies of RNA per milliliter, which is usually found nearly 2 to 3 weeks after the initial HIV infection.
• Using fourth generation immunoassays  which detect the presence of p24 protein upto 10 picograms per milliliter, which usually occurs about 3 to 4 weeks after the initial HIV infection.

Advantage of the Biosensor

The biosensor can detect low concentrations of p24, up to 100,000 times lower than that detected by the fourth generation immunoassays and 100 times lower than methods that are used for identifying the presence of viral RNA.

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The undetectable phase of the HIV infection is reduced to one week, providing early detection and better care.

Importance of Early Detection of HIV

The current methods of detection require approximately 4 weeks for identifying HIV infection. During this time there is

• Irreversible reduction in the CD4 lymphocytes in the gut
• Multiplications of the virus in the central nervous system
• Occurrence of HIV reserves

Moreover, the initial stages of infection are very critical as the potential to infect another person is very high. Apart from the risk of spreading the infection, increased period of infection leads to irreparable damage to the immune system of the host, therefore early detection will facilitate faster administration of anti-retroviral infections.

AIDS/ HIV

Human immunodeficiency virus (HIV) affects the immune system of the host by attacking the CD4 lymphocytes which are important for fighting infection. This increases the risk for serious infections as well as for the development of cancer.

Acquired immunodeficiency syndrome (AIDS) is the condition caused by HIV infection and is considered to be the final stage of infection. It could take weeks to months for an HIV infected individual to develop AIDS.

The spread of HIV infection is mostly through

• Unprotected intercourse with an infected person.
• Sharing needles
• Transmission from an infected mother to the unborn child.

The initial symptoms of the infection are characterized by flu like symptoms as well as swollen glands. The lowered immunity caused due to the infection results in the development of associated infections, most common of those is tuberculosis.

The biosensors will aid in detecting the infection early which can be used to administer antiretroviral infections before there is complete depletion of the CD4 cells. This would aid in better health among HIV infected individuals, lowering the risk of acquiring other severe infections.

References:

1. HIV/AIDS - (https://medlineplus.gov/hivaids.html)

Source-Medindia