Biomedical Engineering Reference
In-Depth Information
[69]. Chitosan has been successfully electrospun together with alginate,
poly(ethylenoxide) (PEO), poly(vinyl alcohol) (PVA), silk i broin and
many other synthetic and natural polymers [70]. h e co-spinning of chi-
tosan with these bioactive substances may confer favourable properties to
the nanoi bres. One such example is the synthesis of hydroxyapatite (HA)
containing chitosan nanoi bres. h e presence of HA promotes cell attach-
ment, osteoblast proliferation and the production of bone extracellular cell
matrix when used as scaf olds for wound healing [71]. Commercially avail-
able nanoi bres are increasing, thus paving the way for advanced health-
care materials R & D. One of the most successful products which are based
on chitosan electrospun nanoi bres is the haemostatic wound dressings
manufactured by Hemcon Inc [72].
5.6 VisualisingNanostructures
Structures at the nano level are typically visualised using high powered
microscopes. With the help of these microscopes, the morphology and
surface & characteristics of nanomaterials can be observed. h e renewed
interest in nanotechnology in recent years brought attention to visuali-
sation techniques. Selected imaging devices can be categorized starting
with those that image materials from the surface proi le, right down to the
nanoscale or atomic level.
h e atomic force microscope (AFM) is commonly used to observe the
surface topology of nanomaterials. h is technique utilizes a cantilever with
a tip made of either a ceramic or a semiconducting material which moves
on the surface of the sample. A laser measures the del ection of the beam
from the surface producing a proi le of the surface. h e laser beam operates
at a wavelength of 1300 nm. h e AFM produces three-dimensional images
of the surface. Advantages of this technique include minimal sample prep-
aration and sample analysis can be carried out in dif erent environments
such as ambient conditions, in liquids, and in ultra-high vacuum over a
large temperature range [73]. A disadvantage with this technique is that the
widths of nano-objects may be overestimated due to tip sharpness. Object
resolution depends on the sharpness of the tip. h is problem can be solved
by using deconvolution algorithms to correct for the overestimation [74].
AFM can also be used to manipulate objects at the nanoscale [75]. h is
technique has been successfully utilized to visualise chitosan [76]. AFM
studies on chitosan are relatively new and only a few studies investigate
chitosan properties on a molecular level in relation to its interaction with
surfaces. h e application is yet to be exploited with biomedical materials. A
