## 3 Results and Discussion  
**Genipin-glycated collagen:** The glycation of collagen using genipin resulted in a color change between the control and glycated gels (Figure 1). In addition, the treatment of gels between pre- and post-glycation also resulted in a color change. The control collagen gels were uniformly a translucent white color (Figure 1a), while glycated gels turned blue and brown when they were pre- or post-glycated, respectively (Figure 1b-e). Pre-glycated samples were consistently darker than post-glycated samples, pointing to the possibility that pH has an effect on the color that genipin turns. In the case of pre-glycated gels, genipin was present when the scaffolds were neutralized with 0.5 M NaOH, while the post-glycated gels were already polymerized and no pH adjustment took place. Color change of genipin-crosslinked gel has been previously reported [6; 8]. Genipin is often used as a blue dye in the food industry, and has been reported to change color depending on the amino acid with which it reacts [6]. Other pigments derived from genipin glycation were blue-green, green, purple, and black [9]. Browning is a common effect of the Maillard reaction by which glycation processes in general take place [9]. **Rheology**: In terms of mechanical testing, glycation with genipin increased the physical properties of the collagen gels across all treatments. As shown in Figure 2, both the storage (G') and loss modulus (G\") values increased with genipin concentration, with the G' of the 22 mM gel exceeding the G' of the control gel nearly 37 times. Using [PERSON]'s multiple pairwise comparison test, G' of all treatments was found to be significantly different (\(p<0.0001\)) from each other, as well as the G\" between treatments. In terms of the mechanical properties of the glycated gels, similar trends of moduli increase have been reported [5]. After a two hour incubation period, [PERSON] reported 0 mM, 1 mM, and 10 mM genipin gels having storage moduli of approximately 80, 90, and 600 Pa, respectively. Similarly, [PERSON] et al., (2019) created genipin gels in comparison to crosslinking agent, EDC [10]. The genipin-crosslinked gels were developed using genipin dissolved in a solution of DMSO and PBS. This resulted in 10 mM gels with  
Figure 1: Gross morphology of lyophilized tissue-engineered cylindrical constructs with genipin-cross-linked collagen: (**a**) control, (**b**,**c**) post-glycated (1 mM and 10 mM), and (**d**,**e**) pre-glycated (13 mM and 22 mM) samples in 24 well plate (well diameter is 14 mm). Scale bar = 6.15 mm. a storage modulus of 100 Pa when tested using a frequency sweep. In the future, further characterization is needed, including degraded fractions and mechanical stability as tissue grows in the scaffold. **AGE Fluorescence:** The presence of AGEs in the collagen scaffolds increased the level of absorbance within the glycated gels when compared to the control (Figure 3). The post-glycated gels followed a near-identical pattern of absorbance with the control gel, albeit at higher absorbance values. However, for the pre-glycated gels, new absorbance peaks formed at around 300-320 nm for both the 13 and 22 mM samples. The decay of absorbance in glycated gels was also measured, as higher levels of glycation correlate with higher rates of degradation [11; 12; 13]. After measuring the total degradation in absorbance between days 1 and 3 of the gels, it was found that the pre-glycated gels experienced a significantly higher degradation rate than the control gels (Figure 3). However, while all glycated gels had higher absorbance rates due to the presence of AGEs, post-glycated gels were found to have similar rates of degradation as the control gel. Figure 3: (**A**) Absorbance measurements of collagen scaffolds compared to pre-(**a**,**b**) and post-glycated scaffolds (**c**,**d**). Measurements were taken on day 1 (**top**, (**a**,**c**)) and day 3 (**bottom**, (**b**,**d**)). Absorbance values were obtained in triplicate and averaged.