BioEnerGel: A mechanically-resilient bioenergetic hydrogel enhances chondrogenic differentiation for cartilage regeneration.

Regeneration of damaged articular cartilage is intrinsically limited by its avascular nature, restricted nutrient transport, and the high bioenergetic demands of damaged chondrogenic cells. Conventional hydrogels often provide mechanical and other biochemical support but fail to sustain cellular bioenergetics required for cartilage matrix formation. Herein, we developed a multifunctional bioenergetic BioEnerGel hydrogel composed of poly (vinyl alcohol) (PVA) reinforced with cellulose nanofibers (CNF), polyglutamic acid (PGA), and crosslinked with tannic acid (TA) to address mechanical, immunomodulatory, and metabolic constraints of cartilage repair. The developed BioEnerGel hydrogel network is stabilized through physical crosslinking and dynamic hydrogen bonding due to presence of CNF and TA, resulting in enhanced mechanical strength (1.47 MPa; mimicking native cartilage modulus), energy dissipation (166.87 kJ·m-3) and resilience under 100 cycles of compressive loading (0.96 MPa). Developed BioEnerGel hydrogel provided antioxidant, anti-inflammatory and tissue-adhesive properties to support better integration with cartilage tissue. Importantly, the incorporation of PGA introduces a bioenergetic component in to BioEnerGel that supports cellular metabolism. In vitro studies demonstrated improved cell metabolism, with 3.5-fold increased intracellular ATP, high mitochondrial membrane potential, and reduced intracellular reactive oxygen species, and 2.2-fold enhanced chondrogenic differentiation, evidenced by increased expression of cartilage-specific markers by ∼4-5 fold including COL2A1 and ACAN, compared to PVA-based commercial (Cartiva®) mimic controls. The composite hydrogel effectively creates a metabolically supportive and mechanically robust microenvironment conducive to cartilage matrix deposition. This bioenergetic hydrogel platform highlights the importance of integrating metabolic regulation with structural design and represents a promising strategy for functional cartilage regeneration and osteoarthritis prevention. STATEMENT OF SIGNIFICANCE: Effective cartilage regeneration is limited by the metabolic demands of damaged chondrogenic cells within an avascular and nutrient-restricted microenvironment. Despite advances in physicochemical properties of hydrogel design, incorporating bioenergetics in hydrogel remains largely overlooked as a governing factor for chondrogenic differentiation and cartilage-matrix synthesis. Herein, we present a bioenergetic-hydrogel that actively supports cellular metabolism, intracellular ATP production, and high mitochondrial membrane potential while maintaining mechanical integrity along with adhesive and immunomodulation required for cartilage-repair. By integrating bioenergetic into the hydrogel, this system enhances chondrogenic differentiation and promotes cartilage-specific matrix formation in comparison to a mechanical commercial-mimic Cartiva. These findings establish bioenergetics as a critical unexplored parameter in cartilage tissue-engineering and provide a new framework for developing bioenergetics-biomaterials aimed at cartilage regeneration.