Bone defects arising from trauma, tumor resection, and infections pose rising scientific challenges [1], [2]. Of explicit significance are instances related to problems of bone mineralization, equivalent to osteoporosis, aging-related bone loss, hypophosphatasia, and X-linked hypophosphatemia [3]. In these pathological situations, the inherent mineral deposition course of is basically impaired, resulting in decreased vitality metabolism, compromised mechanical integrity, and finally, poor regenerative outcomes [3], [4]. Whereas standard bone-graft substitutes, together with metals, ceramics and polymers, usually exhibit enough preliminary energy [5], [6], they sometimes fail to combine biologically or take part dynamically in mineral ion metabolism, limiting their lengthy‑time period efficacy.
To bridge this hole, biomimetic methods have primarily adopted two avenues: the bodily mixing of inorganic phases (e.g., hydroxyapatite particles) [7], and biomineralization through incubation in mineralizing answer [8], [9], [10], [11], [12]. Though mixing composites can enhance preliminary mechanical properties, they usually undergo from macroscopic part separation and poor interfacial integration, resulting in particle leaching and unstable long-term efficiency. Conversely, present biomineralization strategies can produce a extra bone-like hydroxyapatite (HAp) part [13], [14], however mineralization is normally confined to the scaffold floor. This ends in a heterogeneous construction, failing to recapitulate the uniform mineral distribution of native bone tissue.
Pure bone mineralization is a dynamic, spatially orchestrated course of pushed by molecular‑degree synergy between natural and inorganic parts. Phosphorylated proteins sequester Ca2+ to nucleate amorphous calcium phosphate (ACP) precursors inside nanoconfined aqueous domains, subsequently guiding their part transition into crystalline apatite [10], [15], [16]. This bottom-up, self-renewing cycle of ion adsorption, nucleation, and transforming is the essence of bone’s vitality and adaptive capability [17], [18]. Due to this fact, a complicated biomaterial for bone regeneration mustn’t solely present structural assist but in addition incorporate design options that facilitate guided and homogeneous mineralization, approaching the dynamic mineral metabolism noticed in native bone.
Silk fibroin (SF) has garnered consideration owing to its distinctive biocompatibility, tunable biodegradability, and versatile chemical performance [19], [20], [21], [22]. Its negatively charged amino acids can electrostatically entice Ca2+ [23], [24], whereas the nanoconfined areas shaped by its crystalline-amorphous part separation can template HAp nucleation [25], [26], [27]. Consequently, SF‑primarily based programs have been extensively explored for superior manufacturing and biomineralization [14], [28], [29], [30]. Though promising, the present SF-based programs usually depend on static encapsulation and passive mineralization schemes, which don’t adequately replicate the continual and uniform mineral dynamics inherent to physiological bone transforming.
To handle these limitations, we suggest a bioinspired technique primarily based on a molecularly engineered silk composite hydrogel able to guided, homogeneous mineralization. Central to this design is an natural‑inorganic crosslinked bioink (OCB) composed of methacrylate-modified silk fibroin (SilMA), bis(2-methacryloyloxyethyl) phosphate (BMAP), and Ca2+. By Ca2+-mediated coordination, this method allows the homogeneous formation of ACP nanoclusters and establishes an interconnected community of nanoscale ionic channels throughout the hydrogel (Scheme 1A). Utilizing 3D printing, we fabricated photopolymerized hydrogels with tailor-made architectures that mimic the bone microenvironment and the defect geometry (Scheme 1B). The embedded ACP nanoclusters act as nucleation websites, selling gradual part transition to HAp underneath physiologically simulated situations (Scheme 1B). In consequence, the hydrogel reveals mineral-maturing by steady mineral transforming and helps each angiogenesis and osteogenesis in vitro and in vivo (Scheme 1C). By reaching supramolecular-level organic-inorganic synergy built-in by phototriggered dual-crosslinking and Ca2+ coordination, this technique not solely achieves uniform nucleation of ACP all through the community, but in addition overcomes the interfacial weaknesses inherent in conventional composites via its “dynamic hardening functionality.” It thus gives a flexible platform for constructing 3D in vitro bone fashions and for selling regeneration in mineralization‑poor environments in vivo.
