Combined control of matrix additions and co-culture influences MCF10A organisation. (a) Box plots (n = 6) showing bulk oscillatory rheology results of peptide gels with and without matrix modifications, *indicates p < 0.05 relative to all other conditions (one-way ANOVA), (b) acinar morphology on indirect co-culture with HMF, (c) acinar morphology in MCF10A monoculture in 10 mg/mL peptide gels with matrix additions, (d) acinar morphology on indirect co-culture with HMF in 10 mg/mL peptide gels with matrix additions, (e) quantification of acinar diameter for each condition, *indicates p < 0.05 relative to all other conditions (Kruskal-Wallis, >25 acini across 2 independent experiments per condition), (f) immunostaining of an acinus surrounded by collagen I matrix in a 10 mg/mL peptide gel modified with 200 μg/mL collagen I. Scale bar 50 μm.