Novel multifunctional delivery system for chondrocytes and articular cartilage based on carbon quantum dots

Formulating an effective delivery system that facilitates bioactive factors/drugs penetrating dense cartilage surface structure to reach deep zones and repair cartilage injury is a critical and unresolved problem. In this work, carbon quantum dots prepared from m-phenylenediamine (m-CQDs) were used to develop a novel multifunctional delivery system for chondrocytes and cartilage. The proposed delivery system exhibited quick transfection ability (30 min), high transfection effectiveness (exceeding 90%), excellent biocompatibility (92% cell activity) and stable photoluminescence in chondrocytes. Remarkably, the system could effectively reach the chondrocytes in the deep cartilage zones due to its small diameter (4–5 nm). To determine the deliverability of m-CQDs in chondrocytes and cartilage tissues, we prepared m-CQD-HA (i.e., m-CQD carrying oligomeric HA) and evaluated the effect of m-CQD-HA on osteoarthritis chondrocyte model and cartilage tissue. The results showed that m-CQD-HA provided a better treatment effect than HA. In summary, m-CQD is an excellent multifunctional delivery vehicle with small size, high cellular uptake efficiency, exceptional biocompatibility, and integrated imaging function. Most importantly, m-CQDs could help bioactive factors penetrate the dense structure of cartilage surface layer into deep cartilage zones, substantially increasing their therapeutic effect. •m-phenylenediamine-carbon quantum dots (m-CQDs) is an excellent multifunctional delivery vehicle.•m-CQDs could effectively reach the chondrocytes of deep cartilage zones due to the small diameter (4–5 nm) of m-CQDs.•m-CQDs could deliver oligo-HA into the deep cartilage zones and increase substantially the factor’s effectiveness.