Abstract
A new method using a magnetic nanoparticle-based colorimetric biosensing assay (NCBA) was compared with sputum smear microscopy (SSM) for the detection of pulmonary tuberculosis (PTB) in sputum samples. Studies were made to compare the NCBA against SSM using sputum samples collected from PTB patients prior to receiving treatment. Experiments were also conducted to determine the appropriate concentration of glycan-functionalized magnetic nanoparticles (GMNP) used in the NCBA and to evaluate the optimal digestion/decontamination solution to increase the extraction, concentration and detection of acid-fast bacilli (AFB). The optimized NCBA consisted of a 1:1 mixture of 0.4% NaOH and 4% N-acetyl-L-cysteine (NALC) to homogenize the sputum sample. Additionally, 10 mg/mL of GMNP was added to isolate and concentrate the AFB. All TB positive sputum samples were identified with an increased AFB count of 47% compared to SSM, demonstrating GMNP’s ability to extract and concentrate AFB. Results showed that NCBA increased AFB count compared to SSM, improving the grade from “1+” (in SSM) to “2+”. Extending the finding to paucibacillary cases, there is the likelihood of a “scant” grade to become “1+”. The assay uses a simple magnet and only costs $0.10/test. NCBA has great potential application in TB control programs.
Highlights
One third of the world’s population carries an asymptomatic infection from Mycobacterium tuberculosis (Mtb)
This paper reports the use of a glycan-functionalized magnetic nanoparticle-based colorimetric biosensing assay (NCBA) that can be used to capture and increase the acid-fast bacilli (AFB) count in pulmonary tuberculosis (PTB) positive sputum samples without the use of expensive and temperature-sensitive antibodies
The results show that 0.4% NaOH/4% NALC yielded the best performance, as indicated by the higher AFB count in NCBA, with an overall 143% increase over sputum smear microscopy (SSM) (Table 1)
Summary
One third of the world’s population carries an asymptomatic infection from Mycobacterium tuberculosis (Mtb). Mtb and can identify the most infectious patients in areas where there is a high TB prevalence [2]. This test is easy to perform, inexpensive, provides rapid results and does not require complex laboratory equipment, it has considerable drawbacks [3]. The clinical sensitivity of this test is highly variable (20–80%) with much lower sensitivity in paucibacillary cases, such as in immunocompromised or pediatric patients where the bacterial load is usually fewer than 5,000–10,000 acid-fast bacilli (AFB)
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