6.1 Introduction
111
We have introduced reactive homopolymer ultrathin films based on poly(Nsuccinimidyl methacrylate) (PNHSMA) as platforms for biomolecule immobilization with high molecular loading (see Chap. 4). These and related polymer systems
(Chap. 5) possess several advantages compared with other polymer films and in
particular compared with monolayers. Firstly, a large fraction of activated ester side
groups of PNHSMA are exposed, which are very reactive toward nucleophiles [24].
Secondly, the coupling reactions are not limited to the very surface of the films.
Thus, these films are appropriate to anchor a large variety of molecules, including
amino-terminated DNA, proteins and synthetic polymers, in high coverages (reactive
quasi-3D film structure) (see Chap. 4). Thirdly, ultrathin films of PNHSMA can be
easily prepared by spin-coating and the film thickness is tunable. This may help to
contribute to solve the problem of fluorescence quenching due to energy transfer to
the underlying metal substrate in optical detection schemes, such as fluorescenceenhanced SPR [25]. Finally, the very good stability of PNHSMA compared with
other functionalized polymers (e.g., poly (ethylene imine) is water soluble [13]) can
expand the application of the polymer in preparing new platforms.
In this chapter, the PNHSMA-based platforms are expanded to patterned
biomolecular films. These patterned platforms can be conveniently fabricated using
a simple two-step procedure exploiting reactive microcontact printing followed by
wet chemical derivatization. The robustness of the PHNSMA platform, the quasi-3D
loading, and the versatility of reactive microcontact printing together with predictable
coupling of biomolecules from buffered solution render this approach attractive for
the fabrication of bioreactive screening platforms.
6.2 Approaches for Micropatterning of PNHSMA Films
For the fabrication of bioreactive micropatterns using reactive polymer thin films,
a simple, yet robust procedure was developed. Surface patterns were obtained by
reactive microcontact printing of PEG 500 -NH 2 on spin-coated films of PNHSMA
on oxidized silicon, followed by backfilling with the corresponding aminofunctionalized compounds in solution. This coupling reaction leads to a robust,
irreversible immobilization via the formation of covalent amide bonds.
The approach is depicted schematically in Scheme 6.1. Essential for the successful
realization of the approach is the controlled covalent coupling of a densely grafted
layer of PEG, a sufficiently effective function of this blocking layer, the retention of
reactivity of NHS esters in the unreacted areas, as well as the absence of restructuring/
reorientations of the polymer–solution interface.
111
We have introduced reactive homopolymer ultrathin films based on poly(Nsuccinimidyl methacrylate) (PNHSMA) as platforms for biomolecule immobilization with high molecular loading (see Chap. 4). These and related polymer systems
(Chap. 5) possess several advantages compared with other polymer films and in
particular compared with monolayers. Firstly, a large fraction of activated ester side
groups of PNHSMA are exposed, which are very reactive toward nucleophiles [24].
Secondly, the coupling reactions are not limited to the very surface of the films.
Thus, these films are appropriate to anchor a large variety of molecules, including
amino-terminated DNA, proteins and synthetic polymers, in high coverages (reactive
quasi-3D film structure) (see Chap. 4). Thirdly, ultrathin films of PNHSMA can be
easily prepared by spin-coating and the film thickness is tunable. This may help to
contribute to solve the problem of fluorescence quenching due to energy transfer to
the underlying metal substrate in optical detection schemes, such as fluorescenceenhanced SPR [25]. Finally, the very good stability of PNHSMA compared with
other functionalized polymers (e.g., poly (ethylene imine) is water soluble [13]) can
expand the application of the polymer in preparing new platforms.
In this chapter, the PNHSMA-based platforms are expanded to patterned
biomolecular films. These patterned platforms can be conveniently fabricated using
a simple two-step procedure exploiting reactive microcontact printing followed by
wet chemical derivatization. The robustness of the PHNSMA platform, the quasi-3D
loading, and the versatility of reactive microcontact printing together with predictable
coupling of biomolecules from buffered solution render this approach attractive for
the fabrication of bioreactive screening platforms.
6.2 Approaches for Micropatterning of PNHSMA Films
For the fabrication of bioreactive micropatterns using reactive polymer thin films,
a simple, yet robust procedure was developed. Surface patterns were obtained by
reactive microcontact printing of PEG 500 -NH 2 on spin-coated films of PNHSMA
on oxidized silicon, followed by backfilling with the corresponding aminofunctionalized compounds in solution. This coupling reaction leads to a robust,
irreversible immobilization via the formation of covalent amide bonds.
The approach is depicted schematically in Scheme 6.1. Essential for the successful
realization of the approach is the controlled covalent coupling of a densely grafted
layer of PEG, a sufficiently effective function of this blocking layer, the retention of
reactivity of NHS esters in the unreacted areas, as well as the absence of restructuring/
reorientations of the polymer–solution interface.