Karan Saxena

Research Area

Developing Highly Sensitive Immunoassays for Point-of-Care Diagnostics

The immune system’s remarkable ability to produce highly specific antibodies has laid the foundation for a powerful class of diagnostic tools known as immunoassays. These tests detect target biological molecules—called antigens—by capturing them with matching antibodies, much like a lock and key. One of the most familiar examples is the home pregnancy test, which detects the hCG hormone using this principle.

Lateral flow immunoassays (LFAs), often in the form of strip tests, have brought diagnostics to the most remote and underserved corners of the world. However, a major limitation of these tests is their relatively low sensitivity. My research focuses on overcoming this challenge. The goal is to create next-generation lateral flow assays that are not only ultra-sensitive and reliable but also affordable and accessible for real-world point-of-care use in resource-limited settings.

Novel Hair-Dye Inspired Substrates for Enzyme-Enhanced Lateral Flow Assays

In our recent work, we introduced a new class of chromogenic substrates for horseradish peroxidase (HRP)-based lateral flow immunoassays, inspired by the oxidative chemistry of permanent hair dyes. These substrates, comprising a primary intermediate and a coupler, undergo HRP-catalysed oxidative coupling to generate intense colour signals, dramatically enhancing assay sensitivity. Using this strategy, we achieved a sub-ng/mL limit of detection (LoD) for human IgG—0.16 ng/mL (1.07 pM)—which is over 40 times more sensitive than conventional gold nanoparticle-based LFAs. Importantly, these substrates are ~10,000 times more cost-effective than standard enzyme substrates like DAB and TMB, making them ideal for low-cost point-of-care diagnostics in resource-limited settings.

Read this research article here.

🔍 Key Highlights of This Research

• 💡 Inspired by Hair Dye Chemistry: Novel substrates mimic oxidative coupling reactions used in permanent hair dyes.
  
  

• 🎯 Ultra-Sensitive Detection: Achieved a limit of detection of 0.16 ng/mL (1.07 pM) for human IgG.
  
  

• ⚗️ HRP-Catalyzed Color Development: Substrates generate intense color via enzymatic reaction with H₂O₂.
  
  

• 💰 ~10,000× More Cost-Effective: Compared to standard substrates like DAB and TMB.
  
  

• 📈 40× More Sensitive: Than conventional gold nanoparticle-based lateral flow assays.
  
  

• 🌍 Designed for Low-Resource Settings: Affordable and accessible for real-world point-of-care diagnostics.