PB@BPNSs@CS

Stages

1. 1.
   Cargo loading and formulation build(library_build)

   This stage creates the NIR-responsive sustained-release therapeutic formulation.

   Selection: Bind PDGF-BB to 2D black phosphorus nanosheets and fabricate PB@BPNSs@CS microspheres.

2. 2.
   Physicochemical and binding characterization(functional_characterization)

   This stage verifies that the intended formulation was formed and that PDGF-BB is associated with the nanosheets.

   Selection: Characterize morphology, polydispersity, zeta potential, and verify binding efficacy.

3. 3.
   Release performance testing(secondary_characterization)

   This stage tests whether the formulation solves the short half-life and rapid clearance problem motivating the study.

   Selection: Assess sustained and controllable release by ELISA.

4. 4.
   Cell biocompatibility assessment(confirmatory_validation)

   This stage checks whether the formulation is compatible with chondrogenic cells before or alongside in vivo efficacy testing.

   Selection: Evaluate biocompatibility with ATDC5 cells using Cell Counting Kit-8 assay.

5. 5.
   Mouse osteoarthritis efficacy testing(in_vivo_validation)

   This stage tests whether the controlled-release formulation translates into therapeutic benefit in vivo.

   Selection: Assess therapeutic efficacy in a mouse DMM osteoarthritis model using histological staining and immunochemistry.

6. 6.
   Human tissue and molecular mechanism confirmation(confirmatory_validation)

   This stage is used to confirm pathway relevance beyond the mouse model and cultured cells.

   Selection: Analyze human cartilage samples and perform western blot and immunofluorescence to assess signaling pathway involvement.

Steps

1. 1.
   Bind PDGF-BB to 2D black phosphorus nanosheetsengineered formulation intermediate

   Load the therapeutic cargo onto an NIR-responsive carrier.

   Cargo loading is required before microsphere fabrication so the final formulation contains the intended therapeutic complex.

2. 2.
   Fabricate PB@BPNSs@CS microspheresfinal engineered therapeutic formulation

   Create the sustained-release microsphere delivery system.

   Microsphere fabrication follows cargo loading to encapsulate the loaded nanosheet complex into the final delivery matrix.

3. 3.
   Characterize morphology and particle propertiesassayed formulation

   Verify morphology, polydispersity, and zeta potential of the nanosheet formulations.

   Characterization is performed after formulation build to confirm the physical properties of the assembled material before biological testing.

4. 4.
   Verify PDGF-BB binding efficacyassayed formulation

   Confirm that PDGF-BB is successfully associated with the nanosheet carrier.

   Binding verification reduces the risk of interpreting downstream release or efficacy data from an incompletely loaded formulation.

5. 5.
   Assess sustained and controllable releaseassayed formulation

   Measure whether the formulation provides long-term and controllable PDGF-BB release.

   Release testing is needed before efficacy interpretation because sustained and controllable delivery is the central engineering objective of the formulation.

6. 6.
   Evaluate biocompatibility in ATDC5 cellsassayed formulation

   Test whether the formulation is biocompatible with chondrogenic cells.

   Biocompatibility testing helps guard against toxicity before or alongside in vivo therapeutic evaluation.

7. 7.
   Test therapeutic efficacy in mouse DMM osteoarthritistherapeutic formulation under test

   Determine whether a single administration alleviates osteoarthritis in vivo.

   In vivo testing follows formulation and preliminary characterization to evaluate whether the engineered release properties translate into therapeutic benefit.

8. 8.
   Analyze human cartilage and pathway markers

   Confirm findings in human OA cartilage and assess relevance of the identified signaling pathway.

   Human tissue analysis is used as a later confirmation step to extend disease relevance after cell and mouse findings.

9. 9.
   Probe molecular mechanism by western blot and immunofluorescence

   Investigate whether PI3K/AKT/GSK-3β/SOX9 signaling explains the observed chondrogenic and therapeutic effects.

   Mechanism probing is performed after efficacy observations to explain how the formulation and PDGF-BB exert their effects.