Advances in Paper-Based Sensors for the Detection of Antibiotic-Resistant Bacteria

Background

Antimicrobial resistance (AMR) is one of the most significant global public health challenges today. With the extensive use and misuse of antibiotics, more and more bacteria have developed resistance, rendering traditional treatments ineffective. According to the Global Burden of Disease Study data, approximately 7.7 million deaths in 2019 were attributed to bacterial infections, many of which were associated with AMR. The rapid spread of antibiotic-resistant bacteria not only increases healthcare costs but also prolongs hospital stays and significantly boosts mortality rates. Thus, developing rapid, accurate, and cost-effective methods to identify antibiotic-resistant bacteria has become a critical focus in medical and biosensing research.

Paper-based sensors have gained widespread attention in recent years as low-cost and portable solutions for pathogen detection. These sensors can detect target bacteria rapidly through simple color changes or fluorescence signals, making them especially suitable for resource-limited settings. This article reviews the applications of paper-based sensors in detecting antibiotic-resistant bacteria, discussing their advantages, limitations, and future directions.

Source of the Paper

This paper, jointly authored by Aayushi Laliwala, Ashruti Pant, Denis Svechkarev, Marat R. Sadykov, and Aaron M. Mohs, hails from institutions such as the University of Nebraska Medical Center and the University of Nebraska at Omaha. It was published in 2024 in the journal npj Biosensing, titled “Advancements of Paper-Based Sensors for Antibiotic-Resistant Bacterial Species Identification.”

Key Content of the Paper

1. Mechanisms of Antimicrobial Resistance and Detection Tools

Antimicrobial resistance refers to a microorganism’s ability to survive standard antibiotic treatments. Bacteria can develop resistance either through intrinsic resistance, which is naturally encoded in their chromosomes, or acquired resistance mechanisms, such as horizontal gene transfer or genetic mutations. For example, Staphylococcus aureus acquires the mecA gene to develop resistance to methicillin, leading to methicillin-resistant Staphylococcus aureus (MRSA).

Traditional methods for antibiotic susceptibility testing (AST), such as broth dilution, agar dilution, and disc diffusion tests, are time-consuming, often requiring 2–3 days for results. In recent years, molecular techniques such as polymerase chain reaction (PCR) and genomic sequencing have shown promise for rapid detection of resistance genes. However, these remain dependent on sophisticated equipment and skilled technical staff.

2. Advantages and Applications of Paper-Based Sensors

Paper-based sensors are ideal tools for detecting antibiotic-resistant bacteria due to their low cost, portability, and ease of use. Typically made from cellulose, these sensors are hydrophilic and can transport samples via capillary action to the detection zones. Paper-based sensors can detect target bacteria via colorimetric, fluorescent, or electrochemical signals and are suited for resource-limited environments.

Detection targets for paper-based sensors include whole bacterial cells, nucleic acids, and enzymes. Whole-cell detection focuses on observing bacterial growth dynamics in the presence of antibiotics to gauge resistance. For instance, researchers have developed a paper-based AST chip by printing wax-based microchannels on chromatography paper. This chip immobilizes antibiotics and chromogenic substrates within test zones, and bacterial activity in the presence of antibiotics triggers visual color changes (e.g., blue to pink), enabling rapid identification of resistant strains.

3. Detection Techniques for Paper-Based Sensors

Paper-based sensors primarily employ the following detection techniques:

• Colorimetric Detection: Detects target bacteria through visible color changes of chromogenic substrates. For example, tetrazolium salts can serve as substrates for detecting bacterial metabolic activity.
• Fluorometric Detection: Utilizes fluorescent dyes to detect target bacteria. For instance, SYBR Green I has been used for identifying resistance genes in MRSA.
• Surface-Enhanced Raman Spectroscopy (SERS): Relies on nanostructured surfaces to enhance Raman scattering signals, enabling detection of low-concentration target molecules. For example, silver nanoparticles as SERS substrates can detect β-lactamase activity associated with antibiotic resistance.

4. The Role of Nanoparticles in Paper-Based Sensors

Nanoparticles play a vital role in enhancing the sensitivity and functionality of paper-based sensors due to their unique optical properties and ability for functionalization. For example, researchers have developed paper-based sensors incorporating metal-organic frameworks (MOFs) coated with chromogenic substrates like bromothymol blue and nitrocefin. This type of sensor can detect antibiotic-resistant Escherichia coli by indicating changes in pH and β-lactamase activity through colorimetric reactions. The addition of nanoparticles also enables multiplex detection, allowing simultaneous identification of multiple resistance genes or enzymes.

5. Challenges and Future Directions for Paper-Based Sensors

Despite their promise, paper-based sensors face challenges before being widely adopted as clinical diagnostic tools. For example, antibody-based sensors, while highly sensitive, often involve high production costs and demanding storage requirements. Quantitative detection also remains a limitation, as many paper-based sensors are designed primarily for qualitative or semi-quantitative analysis.

Future directions include integrating smartphones or other portable devices for quantitative analysis, developing novel sensing elements such as aptamer-based sensors, and enabling multiplex detection and sample preparation capabilities. Additionally, advanced designs could facilitate dynamic sampling with technologies like soft microneedles.

Significance and Impact of the Paper

This paper provides a comprehensive review of advancements in paper-based sensors for detecting antibiotic-resistant bacteria, detailing their detection techniques, applications, and future directions. Paper-based sensors, as low-cost, portable, and easy-to-use diagnostic tools, are especially beneficial in resource-limited settings, offering significant public health value. Through the integration of nanotechnology and multiplex detection, paper-based sensors hold potential to become mainstream tools for combating antibiotic resistance worldwide.

Key Highlights

• Low Cost and Portability: Leveraging inexpensive paper materials, these sensors are ideal for resource-limited regions.
• Rapid Detection: Using colorimetric or fluorescent methods, paper-based sensors can detect antibiotic-resistant bacteria within hours.
• Multiplex Detection: Integrated with nanotechnology, these sensors offer the capability to detect multiple resistance genes or enzymes simultaneously.
• Future Potential: Combining with portable devices like smartphones, paper-based sensors may further expand their clinical applications.

This paper serves as an essential reference in the field of antibiotic-resistant bacteria detection and provides direction for the future development of paper-based sensors.