Nanosensors for Continuous and Noninvasive Monitoring of Mesenchymal Stem Cell Osteogenic Differentiation

Assessing mesenchymal stem cell (MSC) differentiation status is crucial to verify therapeutic efficacy and optimize treatment procedures. Currently, this involves destructive methods including antibody-based protein detection and polymerase chain reaction gene analysis, or laborious and technically challenging genetic reporters. Development of noninvasive methods for real-time differentiation status assessment can greatly benefit MSC-based therapies. This report introduces a nanoparticle-based sensing platform that encapsulates two molecular beacon (MB) probes within the same biodegradable polymeric nanoparticles. One MB targets housekeeping gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as an internal reference, while another detects alkaline phosphatase (ALP), a functional biomarker. Following internalization, MBs are gradually released as the nanoparticle degrades. GAPDH MBs provide a stable reference signal throughout the monitoring period (18 days) regardless of differentiation induction. Meanwhile, ALP mRNA undergoes well-defined dynamics with peak expression observed during early stages of osteogenic differentiation. By normalizing ALP-MB signal with GAPDH-MB, changes in ALP expression can be monitored, to noninvasively validate osteogenic differentiation. As proof-of-concept, a dual-colored nanosensor is applied to validate MSC osteogenesis on 2D culture and polycaprolactone films containing osteo-inductive tricalcium phospate.