Sustainable Carbododiimine and Triazine Reagents as Collagen Cross-Linking Agents in the Presence of PAMAM Dendrimers

Polyamidoamide Dendrimers and Cross-Linking Agents for Stabilized Bioenzymatic Resistant Metal-Free Bovine Collagen

“…Since the cross-linking reaction can be influenced by the pH of the medium, a set of experiments was carried out to determine the best pH value for each cross-linking agent. In agreement with the literature, we found that a slightly acidic medium (pH = 5.5) promotes the reaction with EDC/NHS [36,37], while the pH of the tanning bath marginally affected DMTMM efficiency (5.0–9.0 range) [31]. Accordingly, all further tests with DMTMM were carried out at pH 7.0.…”

“…Surprisingly, all Ts data reported in Table 2 achieved by treating bovine collagen powder with DMTMM and a PAMAM dendrimer are lower than the stabilization values reached with DMTMM alone [23,31]. In agreement with the literature, we assume that the lower Ts values measured are a consequence of a decrease in the number of cross-linking bonds.…”

“…The Ts data obtained using EDC/NHS in combination with PAMAM dendrimers are presented in Table 1. Cross-linking experiments were carried out according to the protocol optimized in our previous work [31], employing a fixed molar amount of dendrimer, regardless of its generation. Hence, each generation contributes with a different number of free NH 2 groups, i.e., zero generation with 4 NH 2 and first generation with 8.…”

“…[8,28,29,30]. Preliminary studies carried out employing an amine-rich dendrimer in combination with EDC/NHS and DMTMM gave encouraging results [31]; thus, the aim of this work is to highlight the different activity of EDC/NHS and DMTMM as cross-linking agents in combination with Tomalia-type PAMAM dendrimers (Scheme 1) and their effect on collagen biostability. In Figure 1, the structure of PAMAM dendrimers employed in this work is reported, along with the structure of two new 1,5-diamino-3-azapentane core amine-rich dendrimers (2- Triet -G0.0, 2- Triet -G1.0) synthesized according to Tomalia’s divergent synthetic methodology [32].…”