Laser- and UV-assisted modification of polystyrene surfaces for control of protein adsorption and cell adhesion

doi:10.1016/j.apsusc.2008.08.053

Applied Surface Science

Volume 255, Issue 10, 1 March 2009, Pages 5453-5457

https://doi.org/10.1016/j.apsusc.2008.08.053 Get rights and content

Abstract

An appropriate choice of laser and process parameters enables new approaches for the fabrication of polymeric lab-on-chip devices with integrated functionalities. We will present our current research results in laser-assisted modification of polystyrene (PS) with respect to the fabrication of polymer devices for cell culture applications. For this purpose laser micro-patterning of PS and subsequent surface functionalization was investigated as function of laser and process parameters. A high power ArF-excimer laser radiation source with a pulse length of 19 ns as well as a high repetition ArF-excimer laser source with a pulse length of 5 ns were used in order to study the influence of laser pulse length on laser-induced surface oxidation. The change in surface chemistry was characterized by X-ray photoelectron spectroscopy and contact angle measurements. The difference between laser-assisted modification versus UV-lamp assisted modification was investigated. A photolytic activation of specific areas of the polymer surface and subsequent oxidization in oxygen or ambient air leads to a chemically modified polymer surface bearing carboxylic acid groups well-suited for controlled competitive protein adsorption or protein immobilization. Finally, distinct areas for cell growth and adhesion are obtained.

Introduction

In microsystem technology laser-assisted processes are of particular interest to produce devices for micro-fluidics, bio-analytics, bio-reactors and micro-optics [1], [2], [3], [4]. Current state of the art laser processing of polymer materials with respect to laser ablation, micro-patterning and packaging has been described elsewhere [5], [6].

UV-photon induced surface modification of polymers for functionalization of polymer-based micro-devices is a relatively new research field. For this purpose, laser radiation sources or UV-lamp systems may be applied [7], [8], [9], [10]. The main advantage of laser-based technology is its high process flexibility. Three dimensional structures may be modified and a variety of processing conditions can be applied [11], [12]. Excimer laser processing enables high local resolution via direct writing or direct optical imaging of complex mask structures. The process is in general initiated by direct bond breaking which leads to the formation of new bonds or radicals. As a consequence of this the formation or grafting of functional groups, such as amino-groups or carboxyl-groups is possible, which in turn affects protein adsorption and the subsequent adhesion of living eukaryotic, e.g. mammalian, cells.

In this paper different experimental approaches for surface functionalization of polystyrene (PS) will be discussed with respect to spatially controlled protein adsorption and subsequent cell adhesion. For this purpose, modification was performed with laser radiation (wavelength λ = 193 nm) at different laser pulse lengths and with a low-pressure mercury lamp (λ = 185 nm), which operates in a continuous wave mode. This type of modification in combination with laser-assisted microstructuring has been studied for producing polymeric structures used as scaffold for cell culturing applications.

Section snippets

Laser and UV-lamp

Laser-induced structuring and modification based on excimer laser radiation at 193 nm were performed with two different laser pulse lengths, 19 ns (Lambda LPX 210i) and 5 ns (ATLEX-M 300). A high beam homogeneity or “flat top” profile with intensity fluctuation better than 5% were established (more details in [5]). Surface modification of polymers samples by UV-lamp was performed in air using a low-pressure mercury lamp (λ = 185 nm, quartz tube, 15 W) at a 10 cm distance for 60 min [8]. The intensity of

Processing parameters

For the fundamental study of the mechanisms of protein adsorption and cell adhesion, surface modification was performed with a laser fluence of 4 mJ/cm², which is significantly below the ablation threshold of PS by using a laser wavelength of 193 nm [12]. This means that a topographical change of the surface was avoided. In comparison to laser surface modification UV-lamp modification was performed at an effective average intensity of I_L = 280 μW/cm² and the total exposure dose E_tot is controlled in

Summary

Laser patterning of polystyrene was investigated with respect to modification of surface chemistry, surface structuring and micro-drilling. Photo-oxidation and subsequent protein and cell adhesion were observed at very low laser fluences (<9 mJ/cm²) independent of a laser pulse length of 5 ns or 19 ns. The most promising approach for biological and micro-fluidic applications is the successful combination of laser structuring and laser-induced photo-oxidation without changing the processing chamber

Acknowledgments

We gratefully acknowledge the financial support by the program NANOMIKRO of the Helmholtz association and the EU within the Sixth Framework Programme (“Network of Excellence in Multi-Material Micro Manufacture (4M)”).

References (19)

A. Brandenburg et al.
Sens. Actuators B
(1993)
A. Welle et al.
J. Neurosci. Methods
(2005)
W. Pfleging et al.
Appl. Surf. Sci.
(2007)
E. Detrait et al.
J. Neurosci. Methods
(1998)
B. Feng et al.
Biomaterials
(2003)
P.H. Wang et al.
Colloid. Polym. Sci.
(2001)
C.G. Khan Malek
Anal. Bioanal. Chem.
(2006)
E. Gottwald et al.
Lab. Chip
(2007)
D.A. Chang-Yen et al.
Proc. SPIE
(2003)

There are more references available in the full text version of this article.

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Laser- and UV-assisted modification of polystyrene surfaces for control of protein adsorption and cell adhesion

Abstract

Introduction

Section snippets

Laser and UV-lamp

Processing parameters

Summary

Acknowledgments

Sens. Actuators B

J. Neurosci. Methods

Appl. Surf. Sci.

J. Neurosci. Methods

Biomaterials

Colloid. Polym. Sci.

Anal. Bioanal. Chem.

Lab. Chip

Proc. SPIE