Difference Between Radioactive and Nonradioactive Probes

The key difference between radioactive and nonradioactive probes is that radioactive probes are single-stranded DNA or RNA sequences that are labeled with radioactive isotopes while nonradioactive probes are single-stranded DNA or RNA sequences that are labeled with a chemical tag or a fluorescent tag.

Nucleic acid hybridization is an important technique in molecular biology, especially in microbial diagnosis. It helps to identify or detect a particular nucleic acid sequence. In this technique, nucleic acids are fixed to a solid surface and hybridized with a probe. A probe is a fragment of DNA or RNA that is complementary to a sequence of interest. If the target sequence is present in the sample, the probe will hybridize with it and make it detectable. There are two types of probes as radioactive and nonradioactive probes. Therefore, we can tag the probes with a radioactive tag or a fluorescent tag.

CONTENTS

1. Overview and Key Difference
2. What are Radioactive Probes
3. What are Nonradioactive Probes
4. Similarities Between Radioactive and Nonradioactive Probes
5. Side by Side Comparison – Radioactive vs Nonradioactive Probes in Tabular Form
6. Summary

What are Radioactive Probes?

Radioactive probes are the single-stranded DNA or RNA fragments with a radioactive tag. Radioisotopes are used in preparing radioactive probes. Radioisotopes ³²P, ³³P and ³⁵S are commonly used in the labeling of probes. Moreover, radioisotopes ³H and ¹²⁵1 are also used to a lesser extent in the labeling of probes. But they are used for specific applications. Among different radioisotopes, ³²P is the most commonly used isotope in labelling radioactive probes.

Radioactive probes provide a higher degree of reliability and specificity. Therefore, they provide maximum sensitivity and allow accurate quantification of target sequences. However, there are several disadvantages associated with radioactive probes. They have short half-lives. Moreover, they are hazardous and production, use and disposal are problematic when handling. In addition, radioactive probe preparation is a costly process. Therefore, due to the safety issues and cost, radioactive probes are not used as nonradioactive probes nowadays.

What are Nonradioactive Probes?

Nonradioactive probes are the second type of probes that are chemically labelled. Digoxigenin is a nonradioactive probe, which is an antibody-based marker. Digoxigenin probes are specific and sensitive. Biotin is another label used in nonradioactive probe preparation. Biotin/Streptavidin and Digoxigenin/Antibody-detection systems are the most commonly used nonradioactive probes in hybridization. Furthermore, horseradish peroxidase system is another nonradioactive probe system. Once these nonradioactive probes are hybridized with the target sequences, they can be detected via autoradiography or other imaging techniques.

Nonradioactive probes are used more often in nucleic acid hybridization than radioactive probes. This is because nonradioactive probes are not associated with hazardous materials. Furthermore, nonradioactive detection methods require shorter exposure times to detect the hybridization signal. However, the steps involved in DNA hybridization with nonradioactive probes are usually tedious and time-consuming. Moreover, commercially available solutions are expensive.

What are the Similarities Between Radioactive and Nonradioactive Probes?

• Radioactive and nonradioactive probes are two types of probes used in nucleic acid hybridization.
• They facilitate the detection of target sequences in the sample.
• Both types of probes are equally sensitive and specific.

What is the Difference Between Radioactive and Nonradioactive Probes?

Radioactive probes are the single-stranded DNA or RNA sequences labeled with radioactive isotopes, while nonradioactive probes are the single-stranded DNA or RNA sequences labeled with a chemical tag. So, this is the key difference between radioactive and nonradioactive probes. Also, radioactive isotopes are hazardous. Hence, radioactive probes are considerably hazardous, while nonradioactive probes are not hazardous.

Moreover, another difference between radioactive and nonradioactive probes is their disadvantages. Short half-lives and the hazards associated with their production, use and disposal are the disadvantages of using radioactive probes. On the other hand, the steps involved in DNA hybridization with nonradioactive probes are usually tedious and time-consuming.

Below infographic shows more comparisons related to the difference between radioactive and nonradioactive probes.

Summary – Radioactive vs Nonradioactive Probes

A probe is a fragment of DNA or RNA that contains a nucleotide sequence which is complementary to the sequence of interest. In order to detect the target sequence, the probes can be labeled radioactively, fluorescently or chemically. Probes bind with complementary sequences in the sample. Radioactive probes are labeled with radioactive isotopes while nonradioactive probes are labeled with biotin, digoxigenin or horseradish peroxidase. Thus, this is the key difference between radioactive and nonradioactive probes.

Reference:

1. “Hybridization Probe”. En.Wikipedia.Org, 2020, Available here.

Image Courtesy:

1. “Results of in situ hybridization of chromosome X and Y BAC probes” By Joanne H. Hsu, Hui Zeng, Kalistyn H. Lemke, Aris A. Polyzos, Jingly F. Weier, Mei Wang, Anna R. Lawin-O’Brien, Heinz-Ulrich G. Weier and Benjamin O’Brien – Joanne H. Hsu et al. “Chromosome-Specific DNA Repeats: Rapid Identification in Silico and Validation Using Fluorescence in Situ Hybridization” Int. J. Mol. Sci. 2013, 14(1), 57-71; doi:10.3390/ijms14010057 (CC BY 3.0) via Commons Wikimedia