The effect of the surface properties of poly(methyl methacrylate) on the attachment, adhesion and retention of fungal conidia

Poly(methyl methacrylate) (PMMA) surfaces, (commercial PMMA (PMMAc), spin coated PMMA (PMMAsc) and a 90% methylmethacrylate/10% 3-methacryloxypropyltrimethoxysilane random copolymer (P(MMA-co-gMPS)) were used to determine the effect of surface properties on conidia biofouling. The contact angles of the substrates demonstrated that the PMMAsc and the P(MMA-co-gMPS) polymer (62.8°) were more wettable than the PMMAc surface (71.0°). The PMMAsc had the greatest roughness value (32.0 nm) followed by the PMMAc (3.0 nm), then P(MMA-co-gMPS) (1 nm). Aspergillus niger 1957 conidia were spherical, smooth and hydrophobic (12.1%). Aspergillus niger 1988 conidia were spherical with spikes and hydrophobic (17.1%). Aureobasidium pullulans was elliptical with longitudinal ridges and hydrophilic (79.9%). Following attachment assays, cPMMA attached the greatest numbers of conidia. Following the adhesion and retention assays (washing step included in the protocol), A. niger 1957 and A. niger 1988 were least adhered to the P(MMA-co-gMPS) surface, whilst A. pulluans was least adhered to the PMMAsc surface. This work demonstrated that in the absence of a washing step, only the surface properties influenced the conidia attachment, whilst in the presence of a washing step, both the properties of the surfaces and the conidia affected conidia adhesion and retention. Hence, the methodology used (with or without a washing step) should reflect the environment in which the surface is to be applied.