An Integrated Microfluidic Platform for Label-Free Sorting and Functional Assessment of Neutrophils in Sepsis

Neutrophil motility dysfunction, including impaired deformation and chemotaxis, contributes to reduced bacterial clearance and uncontrolled infections in sepsis. Dynamic, quantitative assessment of these parameters holds promise for early diagnosis and prognosis, yet no integrated, label-free platform currently enables neutrophil sorting and functional analysis. We developed a microfluidic cell sorting chip (CS chip) capable of isolating white blood cells (WBCs) from ≤50 μL of whole blood with >80% purity and >90% viability. Combined with a cell deformation and chemotaxis detection chip (CD² chip), we established a fully integrated cell sorting and function detection platform (CSFD platform) for comprehensive motility function evaluation within 30 min. The CSFD platform showed excellent reproducibility, with no significant differences in deformation time (T_D) or migration time (T_M) across three independent devices or operators. Clinical testing revealed that neutrophils from patients with sepsis exhibited significantly impaired motility versus healthy controls (T_D: 2.09 ± 0.32 min vs 1.42 ± 0.12 min; T_M: 18.50 ± 2.48 min vs 13.20 ± 1.51 min; both p < 0.01). We further developed a novel neutrophil motility function index (NMF index), integrating T_D and T_M, which correlated strongly and negatively with clinical markers, including SOFA score, CRP, and PCT. These results highlighted the CSFD platform's potential as a rapid, label-free, point-of-care tool for early diagnosis and real-time monitoring of immune dysfunction in sepsis.