In this research was verified the effect of 3D SCA functionalized with aptamers on blood clot formation and, additionally, on osteogenesis. The results showed that the aptamers led to an improvement in PhC patterns, exhibiting greater expression of MSC (CD90) and HSC (CD45 and CD44). The morphological aspect of blood clots formed on chitosan scaffolds with aptamers reveal clear predominance of white blood cells (WBC) in a fibrin mesh enriched with ECM. In the same group was greater ALP and IBS protein labeling and
Tgfβ1 gene expression associated with osteoblastic differentiation. The use of 3D chitosan/
-TCP based SCA in this investigation was carried out because this biomaterial is highly hydrophilic, with excellent biological properties [
15] for 3D SCA elaboration for bone regeneration [
11,
16,
17]. In this context, the 3D biomaterials functionalization has been proposed, aiming the adsorption of specific molecules on the surface, in an attempt to modify its bioactivity and physiology [
18]. Inspired by natural healing hematoma, tissue-engineered SCA/hydrogels and prefabrication strategies attract significant interests in developing functional bone biomaterial [
19].
Here, anti-fibronectin aptamers functionalization was proposed because the FN is a glycoprotein widely available in blood plasma, especially helping in platelet aggregation and fibrinogenesis [
20,
21]. On the other hand, FN will reinforce fibrin mesh formation that will serve for progenitor’s cells recruitment [
22]. In addition, this important ECM protein is indispensable in many physiological processes [
23,
24], being known to participate in early stages of osteogenesis [
25,
26]. The use of blood clot formed in animal model allowed its PhC formation. This method reflects the simultaneous orchestration of immune response along with cellular interactions of the host’s clotting. There are ex vivo models of blood clot formation, where blood is collected and immediately added to SCA [
27]. However, the proper cascade of events that happens in vivo is underestimated. In this study, PhC was created in the calvaria rat’s defects, allowing the release of substantial growth factors (GF’s), MSC and immune cells recruitment and, after that, transported to analysis. With this, we sought to observe the whole process in the coagulum formation mimicking a prohealing microenvironment. It was observed that aptamers induced MSC (CD90) prevalence in PhC. MSC can differentiate into specific cell types [
28] and lead to secretion of various cytokines and chemokines that contribute to OSB differentiation [
29]. This paracrine signaling can influence resident cells, promoting immunomodulatory [
30], anti-apoptotics and antioxidants [
31] effects. Thus, the MSC expressive detection in PhC formed on SCA with APT may, in addition to recruit cell types associated with tissue repair, potentiate the release of substantial GF’s for osteoimmunology. It was also observed a predominance of lymphocytes (CD45) and leukocytes (CD44) in PhC with APT. CD45 is a tyrosine phosphatase receptor protein, an essential regulator of T and B cells, protagonists in innate immune system mediation [
32]. The CD44 is a glycosaminoglycan that participates in cellular interactions with ECM, such as adhesion, motility, and proliferation [
33]. Leukocytes are cells normally present in fibrin clots, being a significant source of cytokines and GF’s, and can act synergistically with platelets present in blood clots [
34]. In addition, some studies report the role of CD44 in ECM stiffness [
33]. Together with various cell types (including MSC), lymphocytes and leukocytes participate in the healing process. The morphology results corroborate with FACS results. The morphology of PhC formed on aptamer functionalized on SCA showed a blood clot enriched with a fibrin mesh composed mainly of different WBC types, which could be blood, MSC or immune cells. As seen in 3D view by multiphoton microscopy, the OSB distribution on PhC formed in SCA with APT showed to be denser and with more cells when compared to the SCA group. This will create a cellular environment conducive to expression of genes associated with osteogenesis, including favoring Tgf
1 stimulation. The functionalization with aptamers resulted in high
Tgfβ1 gene expression observed in RT-PCR assay. Tgf
1 is a chemotactic polypeptide for macrophages and fibroblasts [
35], in addition to having high affinity with ECM proteins, such as FN [
36]. It supports deposition of main ECM components [
37] directly influencing cell differentiation being important in osteogenesis signaling pathway [
38]. Additionally, leukocytes and platelets, cells normally attached to the fibrin meshwork, are rich sources of GF’s [
39] [39]. Thus,
Tgfβ1 expression is indirectly related to WBC adherence and was increased in PhC formed on SCA functionalized with anti-fibronectin aptamers. This fact possibly leads to
Tgfβ1 releases from leukocytes and platelets, acting directly on ECM deposition and osteodifferentiation. In osteodifferentiation, ALP is fundamentally known as an activator of initiating matrix mineralization mechanisms [
40]. This metalloenzyme is easily found on cell surface and in vesicle matrix of some tissues [
41]. When activated, it will induce hydroxyapatite (HA) deposition in vesicles and these will cross cell membranes, releasing HA into ECM [
42]. The HA adhesion to collagen and maturation of this matrix will be assisted by proteins present in ECM, such as BSP. This anionic phosphoprotein will mediate OSB behavior and consolidate mineralized matrix deposition to collagen [
43]. The immunofluorescence performed in this research showed higher ALP and BSP immunolabeling for the SCA+APT group. Despite the limitations of this research, it is possible to infer that the enrichment of a 3D scaffold with anti-fibronectin aptamer modifies coagulation formation patterns favoring osteoblastic behavior in ex vivo assays, amplifying positive effects on osteodifferentiation.