We then studied the degradation behaviour of the bulk polymers. Figure shows the mass loss analysis of bulk materials under physiological conditions, pH 7.4 and 37 °C. A near linear decrease in mass, and hence degradation of the sample was observed for the Ala-APdA (1) and Gly-APdA (2) containing samples. The degradation of the bulk material shows the same trend as the monomer degradation in solution in the order with the alkyne phosphorodiamidate 3 PdA < 1 Ala-APdA < 2 Gly-APdA. Indeed, the bulk material derived from the non-amino acid containing monomer 3 PdA shows only very minimal degradation in the measured timeframe and conditions. This observation suggests that the potentially hydrolysable P-N linkage of 3 PdA, as well as the ester bonds of the TMPMP are highly stable under these mild conditions in this polymer system. Interestingly, while the degradation of the pristine monomers is strongly accelerated at pH 3.0, the pH value has little influence over the degradation process of the bulk material. This observation suggests a very low diffusion rate of solvent into the materials, in concurrence with the findings of Andrianov and Sukhishvili, who propose that diffusivity is rate-determining for the degradation kinetics of hydrophobic bulk materials. The near-linear nature of the degradation process, coupled with the relative pH independence of the degradation rates, suggests a surface erosion mechanism for these polymer systems. Surface erosion, generally expressed by a linear loss in mass over time is a highly desirable yet rarely achieved property for biodegradable materials intended for use as biomaterials. Such behaviour facilitates more uniform and thus predictable mechanical loss degradation and release of bioactives, if used for delivery purposes . Cytotoxicity studies were carried out to provisionally assess the suitability of the novel materials as biological implants, adhering to existing standards for testing medical devices (DIN EN ISO 10993-5). Products leachable within 24 h under physiological conditions showed no influence on the viability of the standard test cell line MC3T3-E1 (Figure ). Good surface adherence of the cells to bulk test specimens was observed, as well as cell-typical growth with doubling times between 27 -35 h (Figure ). ttachment of viable growing cells was detected by fluorescence microscopy on the surface of all material types (Figure ). of hydrolysis could be tuned by choice of amino acid. This property, combined with the good cytocompatibility and celladherence of the materials and the endogenous nature of the main degradation products, makes these materials of significant interest for future development as degradable, 3Dprintable biological scaffolds.