Figure 4.

Different spectra of ¹H and ¹³C nuclear magnetic resonance (NMR) analysis of the hyaluronic acid (HA) filler samples: (A,B) Product 7 has a low MoD but a high CrR value of 0.222 among the tested fillers. (A) The N-acetyl signal (CH₃) from HA and BDPE signals (H5′, H6′) used for the determination of the MOD. MoD ¹H (%) = (Iδ^H1.7/4)/(Iδ^H2.1/3) × 100. (B) The C10′ signals on mono-linked BDPE are the C5′ and C6′ of both mono- and cross-linked BDPE used to determine the CrR, CrR = 1 − I^δC62.7/(I^δC25.2/2). The signals and CH₃ of N-Acetyl glucosamine are used to determine the MoD, MoD (%) = (I^δC25.2/2)/I^{δC21.9−22.6} 100. MoD, degree of modification; CrR, cross-linking ratio.