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7 Reactive μCP on Ultrathin Block Copolymer Films …
7.1 Introduction
The fabrication of biomolecular patterns with dimensions ranging from the millimeter
to 10 μm scale has become important for the development of biosensors, biomaterials, genomic arrays, as well as tissue engineering [1]. For fundamental studies
of cell biology and for future miniaturized applications in the named areas even
smaller patterns are required. Cells and proteins have been previously patterned on
various substrates using self-assembled monolayers (SAMs) [2], metal templates
[3], stamped proteins and peptides [4], bio and comb polymers [5], microfluidic
channels [6], and membranes [7]. As an attractive method to pattern biological
molecules, microcontact printing (μCP) techniques became very popular due to
their simplicity, flexibility, and low cost compared to other techniques [8]. Using
μCP, Khademhosseini et al. [9] have demonstrated a simple process that can be used
to pattern oxide-based substrates with biofouling-resistant polymers (poly(ethylene
glycol)-based random copolymer) with precise control over surface topography. Such
controlled patterns can be used further for patterning proteins and cells. Control of
biopolymer binding and release, or cell attachment on micropatterned materials with
appropriate features fabricated by μCP have been studied in detail [10]. Microarrays
containing up to 16 different proteins were fabricated on polystyrene through physical
adsorption by simple μCP molecular transfer techniques combined with microfluidic
networks [11]. In addition, the preparation of multiprotein arrays on polymer films
by μCP was also studied and tested as a detection system for specific antibodies [12].
After fabrication, immunoassays were successfully carried out using the patterned
protein microarrays. The characterization revealed high quality of the protein deposition and indicated a high degree of selectivity for the targeted antigen–antibody
interactions.
It has been pointed out throughout this book that an important part of the biosensor
design is the (bio)chemical nature of the interfacial layer at the sensor surface.
Compared to SAMs, polymers have several distinct advantages, including low cost,
ease of film preparation, stability, and three-dimensional structure and functionalities
[13]. As an alternative to the PNHSMA system discussed in the previous chapters, the
biomolecular patterning of the PtBA skin layer in PS-b-PtBA polymer thin films will
be treated in this chapter. One additional advantage of the PS 690 -b-PtBA 1210 diblock
copolymer system is the high stability for a broad range of processing conditions
because this diblock copolymer contains a water insoluble polystyrene block (see
Chap. 5). In addition, the microphase separation observed for this block copolymer
offers the possibility to fabricate nanometer scale patterned surfaces, as described in
Chap. 8.
In this chapter, three patterning approaches are discussed to direct the deposition
of biomolecules on PS 690 -b-PtBA 1210 diblock copolymer films, as shown in Fig. 7.1.
In approach (A), two different types of molecules, bovine serum albumin (BSA) and
fluoresceinamine, were directly stamped onto the polymer films in two sequential
reactive μCP steps for covalent binding in micrometer scale patterns. In approach (B),
7 Reactive μCP on Ultrathin Block Copolymer Films …
7.1 Introduction
The fabrication of biomolecular patterns with dimensions ranging from the millimeter
to 10 μm scale has become important for the development of biosensors, biomaterials, genomic arrays, as well as tissue engineering [1]. For fundamental studies
of cell biology and for future miniaturized applications in the named areas even
smaller patterns are required. Cells and proteins have been previously patterned on
various substrates using self-assembled monolayers (SAMs) [2], metal templates
[3], stamped proteins and peptides [4], bio and comb polymers [5], microfluidic
channels [6], and membranes [7]. As an attractive method to pattern biological
molecules, microcontact printing (μCP) techniques became very popular due to
their simplicity, flexibility, and low cost compared to other techniques [8]. Using
μCP, Khademhosseini et al. [9] have demonstrated a simple process that can be used
to pattern oxide-based substrates with biofouling-resistant polymers (poly(ethylene
glycol)-based random copolymer) with precise control over surface topography. Such
controlled patterns can be used further for patterning proteins and cells. Control of
biopolymer binding and release, or cell attachment on micropatterned materials with
appropriate features fabricated by μCP have been studied in detail [10]. Microarrays
containing up to 16 different proteins were fabricated on polystyrene through physical
adsorption by simple μCP molecular transfer techniques combined with microfluidic
networks [11]. In addition, the preparation of multiprotein arrays on polymer films
by μCP was also studied and tested as a detection system for specific antibodies [12].
After fabrication, immunoassays were successfully carried out using the patterned
protein microarrays. The characterization revealed high quality of the protein deposition and indicated a high degree of selectivity for the targeted antigen–antibody
interactions.
It has been pointed out throughout this book that an important part of the biosensor
design is the (bio)chemical nature of the interfacial layer at the sensor surface.
Compared to SAMs, polymers have several distinct advantages, including low cost,
ease of film preparation, stability, and three-dimensional structure and functionalities
[13]. As an alternative to the PNHSMA system discussed in the previous chapters, the
biomolecular patterning of the PtBA skin layer in PS-b-PtBA polymer thin films will
be treated in this chapter. One additional advantage of the PS 690 -b-PtBA 1210 diblock
copolymer system is the high stability for a broad range of processing conditions
because this diblock copolymer contains a water insoluble polystyrene block (see
Chap. 5). In addition, the microphase separation observed for this block copolymer
offers the possibility to fabricate nanometer scale patterned surfaces, as described in
Chap. 8.
In this chapter, three patterning approaches are discussed to direct the deposition
of biomolecules on PS 690 -b-PtBA 1210 diblock copolymer films, as shown in Fig. 7.1.
In approach (A), two different types of molecules, bovine serum albumin (BSA) and
fluoresceinamine, were directly stamped onto the polymer films in two sequential
reactive μCP steps for covalent binding in micrometer scale patterns. In approach (B),