Combinatorial and High-Throughput Screening of Materials ...

ACS Combinatorial Science
show absence of a significant cytotoxicity. In a mechanistic point
of view, biomaterials enter in a three-way interaction with tissue
or blood proteins present in vivo as well as with some cellular
systems. Hence understanding the chemistry of these surfaces
and their subsequent surface-cell interactions is becoming critical
for the design of the perfect organic biomaterials. Such complex
surface interactions have been examined rapidly and effectively
by powerful combinatorial and high throughput methodologies.
Recent advances in cell interactions with biomaterials in an array
form (discrete libraries) or in a gradient form have been recently
reviewed. 436
The most commonly used biodegradable polylactic/glycolic
acid and polycaprolactam materials have been used in the
development of a high throughput cell-material screening strategy,
based upon local cell-feature analysis (LCFA) This methodology
was applied to screen osteoblast proliferation behavior on
combinatorial libraries of phase separated poly lactic/glycolic
acid and polycaprolactam materials. 437 The LCFA method,
based on histograms of distances between cells and microstructures,
was able to identify nonlinear, discrete relationships
between proliferation, PCL diameter, and cell-PCL distance.
Using these results, the authors proposed a model for classifying
the material microstructure interactions, in which small PCL
islands far from the cell nucleus act as holders for attachment and
large islands close to cells act to shape the cell.
Similarly, tyrosine derived biomaterials have been examined
using a high throughput characterization of the cell adhesive
responses to biomaterials. The substrates were made from poly
DTE carbonate and poly DTO carbonate substrates which
corresponding surfaces are made by gradient annealing. 460
Saos-2 cells engineered with a green fluorescent protein (GFP)
reporter for farnesylation (GFP-f) were cultured on the gradient
substrates to assess the effects of nanoscale surface topology and
roughness that arise during the phase separation process on cell
attachment and adhesion strength. The high throughput imaging
approach allowed the rapid establishment of a structure property
relationships between cell adhesion and biomaterial properties.
This study found that cell attachment and spreading
increased monotonically with DTE content and was significantly
elevated at the position with intermediate regions corresponding
to the highest “gradient” of surface roughness, while GFP-f
farnesylation intensity descriptors were sensitively altered by
surface roughness, even in cells with comparable levels of
spreading. Simon et al. highlighted the recent advances on the
use of gradients and arrays for combinatorial screening and
development of biomaterials toward tissue engineering. 436
Langer and co-workers reviewed the use of combinatorial
chemistry and high throughput screening tools to investigate the
optimization of stem cell microenvironments, which are critical
component to cell growth and proliferation. 461 Key studies of
stem cell/biomaterial interactions using combinatorial libraries
of polymers (array of discrete materials or gradient) were
reviewed comprehensively.
An interesting work on the investigation of protein cell
interactions was also highlighted and specifically the high importance
of such interactions in helping the optimization of stem
cell microenvironments. 462 As an example, a diverse set of 496
arrayed materials have been designed and prepared with 16 major
monomers and 6 minor monomers. Combining high throughput
polymer synthesis and rapid quantification of material/protein/
cell interactions, it was possible to quickly map out the interactions
among human embryonic body (hEB) cell attachment,
REVIEW
Figure 50. Mineralization height as a function of various surface
topographies. 463
fibronectin (Fn) adsorption, and the chemical structures structures
of the substrates. Both the major and minor monomers
have been shown to affect Fn adsorption and hEB cell attachment.
Further analysis revealed that the chemistry diversity
created here can generate a diverse collection of materials with
varying amounts of adsorbed Fn and cell adhesion. Controllable
hEB cell attachment was shown to be reproducible on four
polymer films with three distinct cell-attachment capacities, and
the biological properties of the scaled up films were found to be
similar to their microscale counterparts. It was believed the
integrated high-throughput synthesis and rapid quantification
of materials/protein/cell interactions may accelerate the development
of biomaterials for various applications, such as materials-directed
stem cell differentiations. 462
3.5.4. Inorganic Surfaces with Cell Systems. Biomaterials,
including those used as part of body implants, often contain
inorganic components. Work in elucidating and studying surface
interaction between these components attracted increasing
interest. A significant amount of work in the area has already
been reviewed recently by Simon et al. 436 Lovmand et al.
explored the use of combinatorial topographical libraries for
the screening of enhanced osteogenic expression and mineralization.
463 In this study, micro and nanofunctionalized surfaces have
been screened in a combinatorial approach for cell response. This
strategy has the merit to be able to provide crucial information
toward the optimization of the design of the biomaterials that will
be able to regulate cellular differentiation. A library of 504 unique
distinct surfaces (created using the Biosurface structure array
platform) has been screened for the osteoblastic cell line interaction
and subsequent mineralization. Each BSSA is a wafer
which is composed by a 13 13 array with 169 unique area
testers. These platforms have been constructed rapidly using
boron-doped p-type Si-wafers. The “combinatorial patterns”
were created using standard lithography and subsequent etching
processes using Cl 2 ,NF 3 , and HBr. The micro and nanostructured
surfaces of various sizes, shapes and heights which were
obtained were then screened for cellular response and more
particularly osteoblast cell expression and subsequent mineralization.
An example of the effect of mineralization height as a
function of surface topography is shown in Figure 50. Once
exposed to the optimal micro/nano surfaces, the surfaces were
622 dx.doi.org/10.1021/co200007w |ACS Comb. Sci. 2011, 13, 579–633