Purpose: Adoptive cell transfer of tumor-specific T cells is a promising cancer immunotherapy, but efficient and economical ex vivo expansion of T cells remains a bottleneck. Artificial antigen-presenting cells (aAPCs) with high surface area and modular design could overcome cost and scalability limits of dendritic cell–based expansion.
Hypothesis: A carbon nanotube–polymer composite (CNP) presenting T-cell stimuli on bundled carbon nanotubes, combined with PLGA nanoparticles co-encapsulating IL-2 and magnetite, can act as an efficient artificial antigen-presenting cell—expanding T cells to clinically relevant numbers using 1,000-fold less soluble IL-2, and the expanded T cells can delay tumor growth in a murine melanoma model.
Aims: Synthesize and characterize CNPs: bundled carbon nanotubes functionalized with neutravidin, biotinylated MHC-I/peptide and anti-CD28, plus PLGA nanoparticles containing IL-2 and magnetite. - Test in vitro expansion, phenotype, cytokine release, and cytolytic activity of murine OT-1 CD8⁺ T cells versus soluble tetramers, Dynabeads, and CNT-only controls. - Evaluate in vivo anti-tumour activity of CNP-expanded T cells in a B16-OVA murine melanoma model after peritumoral adoptive transfer. - Demonstrate human translation by expanding EBV-specific CD8⁺ T cells from healthy HLA-A2⁺ donors and comparing to dendritic cell stimulation.
Delivery system:
Component: Core material; Details: Hydroxyl-modified, bundled carbon nanotubes (CNTs); ~13 µm assemblies; high surface area (~1,610 m² g⁻¹)
Component: Surface functionalization; Details: Neutravidin adsorbed onto CNTs; biotinylated T-cell stimuli attached
Component: T-cell stimuli; Details: Peptide-loaded MHC-I (H-2Kᵇ/SIINFEKL for OT-1; EBV peptide/HLA-A2 dimer for human) and anti-CD28
Component: Cytokine delivery; Details: PLGA nanoparticles (~264 nm) co-encapsulating IL-2 and magnetite (12 wt% magnetite); DSPE-PEG-biotin surface
Component: Binding strategy; Details: Biotin–neutravidin coupling
Component: Separation; Details: Magnetite enables magnetic separation of CNPs from T cells
Component: Payload; Details: Antigen/MHC complexes, co-stimulatory ligand, and IL-2 cytokine (no genetic payload)
Component: Target cells; Details: CD8⁺ T cells (murine OT-1; human EBV-specific)
Component: Key feature; Details: Paracrine IL-2 delivery and multivalent antigen presentation on a high-aspect-ratio nanotube substrate
Approach: In vitro murine model: OT-1 CD8⁺ T cells isolated from transgenic mice; stimulated with CNPs or controls (¹⁴CNT, Dynabeads, soluble tetramers) with/without exogenous IL-2; some controls received 1,000-fold higher IL-2 (62.5 ng mL⁻¹). - In vivo model: C57BL/6 mice inoculated with B16F10-OVA melanoma for 10 days; single peritumoral injection of 1×10⁶ CNP-activated OT-1 CD8⁺ T cells; n = 6 mice per group; tumour growth monitored for 14 days. - Human translation: CD8⁺ T cells from HLA-A2⁺ healthy donors stimulated with CNP/EBV, CNP/OKT-3, or EBV-pulsed dendritic cells + IL-2 (100 U mL⁻¹); EBV-specific expansion measured at day 7. - Controls: PBS (no treatment), Dynabeads + IL-2 (DYNA-EXO), soluble tetramers + IL-2 (TET-EXO), CNP without IL-2 (CNP), ¹⁴CNT controls.
Key methods: Characterization: TEM, SEM, size distribution, zeta potential, NMR for PEG-biotin, FRET for antigen clustering, adsorption isotherm for neutravidin. - T-cell expansion and phenotype: Coulter counter for fold expansion; flow cytometry for CD27, CD69, CD25, CD62L, CD44, granzyme-B, EBV tetramer. - Function: IFN-γ ELISA; cytolytic activity against B16-OVA target cells; MTS/viability. - In vivo: Tumour volume and mass; tumour-infiltrating lymphocyte (TIL) counts; CD44⁺/CD62L⁻ effector TILs; haematoxylin and eosin histology. - Human T-cell expansion: Flow cytometry for EBV⁺/CD8⁺ frequency.
Key results: Murine T-cell expansion: CNPs expanded OT-1 CD8⁺ T cells ~200-fold after 2 weeks—more than 2× DYNA-EXO and more than 4× TET-EXO. - Cytokine efficiency: Expansion comparable to clinical standards using 1,000-fold less soluble IL-2. - Phenotype/function: >90% CD8⁺/CD27⁺ and CD69⁺/CD25⁺ during first week; higher granzyme-B; cytolytic activity at 20:1 E:T ratio was 3× that of DYNA-EXO. - In vivo efficacy: Significant delay in tumour growth at day 14 vs no treatment; TIL counts ~9×10⁴ for CNP and DYNA-EXO⁺ vs ~1×10⁴ for TET-EXO⁺ and PBS; increased CD44⁺/CD62L⁻ effector TILs; histology showed lymphocyte infiltration and tumour apoptosis. - Human translation: CNP/EBV expanded EBV-specific CD8⁺ T cells to 8.04% vs dendritic cells 2.22% (~4-fold); CNP/OKT-3 reached 4.97% (~2-fold).
Interpretation: The authors claim the CNP composite is a promising platform for generating large numbers of cytotoxic T cells for cancer immunotherapy, offering modularity, off-the-shelf storage, and significant cost reductions by reducing IL-2 dose 1,000-fold while enabling magnetic enrichment. They suggest this artificial APC system may improve antigen-specific T-cell expansion for adoptive cell therapies.
Limitations: In vivo scope: Only one murine melanoma model with peritumoral injection; short 2-week follow-up; no survival or memory T-cell data. - Human validation: Only in vitro; full clinical adaptation was explicitly beyond the scope. - Safety: Long-term fate, biodistribution, and toxicity of carbon nanotubes were not extensively assessed in vivo. - Manufacturing: Magnetic separation may complicate large-scale clinical translation. - Release profile: IL-2 release showed an initial burst followed by sustained release; leaching of iron was negligible but measured only over 150 h. - Controls: Not all clinical expansion standards were compared; 1,000-fold higher IL-2 was used in some controls to match CNP effects, which may not fully reflect conventional protocols.
