Supramolecular antifouling additives for robust and efficient functionalization of elastomeric materials: molecular design matters

The ultimate functionality of elastomeric materials can be largely influenced by the molecular design of antifouling additives that interact through directed hydrogen bonding bisurea motifs. Herein, three additives, composed of matching bisurea groups and antifouling oligo(ethylene glycol) (OEG) functionalities, are judiciously designed. The first additive is composed of one bisurea and one OEG, the second additive of one bisurea and two OEGs, and the third additive of two bisurea and one OEG. On solution-cast films, non-cell adhesive properties are dependent on the amount of incorporated OEG irrespective of the bisurea design; however, on 3D electrospun scaffolds only the additive that consists of two bisurea moieties connected via an OEG functionality ensures proper non-cell adhesive properties. Interestingly, robust non-cell adhesive properties are maintained, both with repeated cell seeding and after partial enzymatic degradation of the scaffold. These results highlight the importance of additive design in supramolecular functionalization and show that translation from simple 2D solution-cast films to 3D electrospun scaffolds is not trivial with respect to additive presentation and functionality

Combinatorial functionalization with bisurea‐peptides and antifouling bisurea additives of a supramolecular elastomeric biomaterial

The bioactive additive toolbox to functionalize supramolecular elastomeric materials expands rapidly. Here we have set an explorative step toward screening of complex combinatorial functionalization with antifouling and three peptide-containing additives in a bisurea-based supramolecular system. Thorough investigation of surface properties of thin films with contact angle measurements, X-ray photoelectron spectroscopy and atomic force microscopy, was correlated to cell-adhesion of endothelial and smooth muscle cells to apprehend their respective predictive values for functional biomaterial development. Peptides were presented at the surface alone, and in combinatorial functionalization with the oligo(ethylene glycol)-based non-cell adhesive additive. The bisurea-RGD additive was cell-adhesive in all conditions, whereas the endothelial cell-specific bisurea-REDV showed limited bioactive properties in all chemical nano-environments. Also, aspecific functionality was observed for a bisurea-SDF1α peptide. These results emphasize that special care should be taken in changing the chemical nano-environment with peptide functionalization

Combinatorial functionalization with bisurea-peptides and antifouling bisurea additives of a supramolecular elastomeric biomaterial

The bioactive additive toolbox to functionalize supramolecular elastomeric materials expands rapidly. Here we have set an explorative step toward screening of complex combinatorial functionalization with antifouling and three peptide-containing additives in a bisurea-based supramolecular system. Thorough investigation of surface properties of thin films with contact angle measurements, X-ray photoelectron spectroscopy and atomic force microscopy, was correlated to cell-adhesion of endothelial and smooth muscle cells to apprehend their respective predictive values for functional biomaterial development. Peptides were presented at the surface alone, and in combinatorial functionalization with the oligo(ethylene glycol)-based non-cell adhesive additive. The bisurea-RGD additive was cell-adhesive in all conditions, whereas the endothelial cell-specific bisurea-REDV showed limited bioactive properties in all chemical nano-environments. Also, aspecific functionality was observed for a bisurea-SDF1α peptide. These results emphasize that special care should be taken in changing the chemical nano-environment with peptide functionalization

Impact of Additives on Mechanical Properties of Supramolecular Electrospun Scaffolds

The mechanical properties of scaffolds used for mechanically challenging applications such as cardiovascular implants are unequivocally important. Here, the effect of supramolecular additive functionalization on mechanical behavior of electrospun scaffolds was investigated for one bisurea-based model additive and two previously developed antifouling additives. The model additive has no effect on the mechanical properties of the bulk material, whereas the stiffness of electrospun scaffolds was slightly decreased compared to pristine PCL-BU following the addition of the three different additives. These results show the robustness of supramolecular additives used in biomedical applications, in which mechanical properties are important, such as vascular grafts and heart valve constructs

Impact of Additives on Mechanical Properties of Supramolecular Electrospun Scaffolds

The mechanical properties of scaffolds used for mechanically challenging applications such as cardiovascular implants are unequivocally important. Here, the effect of supramolecular additive functionalization on mechanical behavior of electrospun scaffolds was investigated for one bisurea-based model additive and two previously developed antifouling additives. The model additive has no effect on the mechanical properties of the bulk material, whereas the stiffness of electrospun scaffolds was slightly decreased compared to pristine PCL-BU following the addition of the three different additives. These results show the robustness of supramolecular additives used in biomedical applications, in which mechanical properties are important, such as vascular grafts and heart valve constructs

Effectiveness of cell adhesive additives in different supramolecular polymers

Supramolecular motifs in elastomeric biomaterials facilitate the modular incorporation of additives with corresponding motifs. The influence of the elastomeric supramolecular base polymer on the presentation of additives has been sparsely examined, limiting the knowledge of transferability of effective functionalization between polymers. Here it was investigated if the polymer backbone and the additive influence biomaterial modification in two different types of hydrogen bonding supramolecular systems, that is, based on ureido-pyrimidinone or bis-urea units. Two different cell-adhesive additives, that is, catechol or cyclic RGD, were incorporated into different elastomeric polymers, that is, polycaprolactone, priplast or polycarbonate. The additive effectiveness was evaluated with three different cell types. AFM measurements showed modest alterations on nano-scale assembly in ureido-pyrimidinone materials modified with additives. On the contrary, additive addition was highly intrusive in bis-urea materials. Detailed cell adhesive studies revealed additive effectiveness varied between base polymers and the supramolecular platform, with bis-urea materials more potently affecting cell behavior. This research highlights that additive transposition might not always be as evident. Therefore, additive effectiveness requires re-evaluation in supramolecular biomaterials when altering the polymer backbone to suit the biomaterial application

Cell and Protein Fouling Properties of Polymeric Mixtures Containing Supramolecular Poly(ethylene glycol) Additives

Fouling properties of new biomaterials are important for the performance of a material in a biological environment. Here, a set of three supramolecular polymeric additives consisting of ureidopyrimidinone (UPy)-functionalized poly­(ethylene glycol) (UPyPEG) were formulated with UPy-modified polycaprolactone into thin supramolecular material films. The antifouling properties of these material films were determined by investigation of the relation of cell adhesion and protein adsorption on these materials films. The presence of the UPyPEG additives at the surface of the films was evident by an increased hydrophilicity. Adhesion of human epithelial and endothelial cells was strongly reduced for two of the UPyPEG-containing films. Analysis of adsorption of the first three proteins from the Vroman series, albumin, γ-globulin, and fibrinogen, using quartz crystal microbalance with dissipation in combination with viscoelastic modeling, revealed that the surfaces containing the UPyPEG additives had a limited effect on adsorption of these proteins. Despite a limited reduction of protein adsorption, UPyPEG-containing mixtures were non-cell-adhesive, which shows that non-cell-adhesive properties of supramolecular polymer surfaces are not always directly correlated to protein adsorption

Supramolecular Additive-Initiated Controlled Atom Transfer Radical Polymerization of Zwitterionic Polymers on Ureido-pyrimidinone-Based Biomaterial Surfaces

Surface-initiated controlled radical polymerization is a popular technique for the modification of biomaterials with, for example, antifouling polymers. Here, we report on the functionalization of a supramolecular biomaterial with zwitterionic poly(sulfobetaine methacrylate) via atom transfer radical polymerization from a macroinitiator additive, which is embedded in the hard phase of the ureido-pyrimidinone-based material. Poly(sulfobetaine methacrylate) was successfully polymerized from these surfaces, and the polymerized sulfobetaine content, with corresponding antifouling properties, depended on both the macroinitiator additive concentration and polymerization time. Furthermore, the polymerization from the macroinitiator additive was successfully translated to functional electrospun scaffolds, showing the potential for this functionalization strategy in supramolecular material systems. ©</p

Functional peptide presentation on different hydrogen bonding biomaterials using supramolecular additives

Supramolecular biomaterials based on hydrogen bonding units can be conveniently functionalized in a mix-and-match approach using supramolecular additives. The presentation of bioactive additives has been sparsely investigated in supramolecular-based elastomeric biomaterials. Here it was investigated how cell adhesive peptides are presented and affect the surface in supramolecular biomaterials based either on ureido-pyrimidinone (UPy) or bisurea (BU) moieties. Polycaprolactone modified with UPy or BU moieties served as the base material. RGD or cyclic (c)RGD were conjugated to complementary supramolecular motifs, and were mixed with the corresponding base materials as supramolecular additives. Biomaterial surface morphology changed upon bioactivation, resulting in the formation of random aggregates on UPy-based materials, and fibrous aggregates on BU-materials. Moreover, peptide type affected aggregation morphology, in which RGD led to larger cluster formation than cRGD. Increased cRGD concentrations led to reduced focal adhesion size and cell migration velocity, and increased focal adhesion numbers in both systems, yet most prominent on functionalized BU-biomaterials. In conclusion, both systems exhibited distinct peptide presenting properties, of which the BU-system most strongly affected cellular adhesive behavior on the biomaterial. This research provided deeper insights in the differences between supramolecular elastomeric platforms, and the level of peptide introduction for biomaterial applications