We designed and fabricated a smart and stimuli responsive membrane to cater on demand molecular transporting applications. A novel photoswitchable peptide (PSP) was synthesized and attached inside nanoporous anodic alumina membranes (NAAMs) pores. The PSP specifically switched between its cis and trans photostationary states on exposure to 364 nm and 440 nm wavelength lights respectively, which not only provided the ability to control its pore diameter but also the surface chemistry. The switchable molecular transport properties of the PSP-NAAMs have been shown as a function of the light exposure. Most importantly, the molecular transport across PSP-NAAMs could be repeatedly switched between on and off state, which is highly significant for on-demand triggered drug release systems.
Current treatment of a number of orthopaedic conditions, for example fractures, bone infection, joint replacement and
bone cancers, could be improved if mechanical support could be combined with drug delivery. A very challenging
example is that of infection following joint replacement, which is very difficult to treat, can require multiple surgeries
and compromises both the implant and the patient’s wellbeing. An implant capable of providing appropriate biomechanics
and releasing drugs/proteins locally might ensure improved healing of the traumatized bone. We propose
fabrication of nanoengineered titanium bone implants using bioinert titanium wires in order to achieve this goal.
Titanium in the form of flat foils and wires were modified by fabrication of titania nanotubes (TNTs), which are hollow
self-ordered cylindrical tubes capable of accommodating substantial drug amounts and releasing them locally. To further control the release of drug to over a period of months, a thin layer of biodegradable polymer PLGA poly(lactic-coglycolic acid) was coated onto the drug loaded TNTs. This delayed release of drug and additionally the polymer
enhanced bone cell adhesion and proliferation.
The concept of a microfluidic biosensing device based on reflective interferometric spectroscopy (RIfS) is presented in
this article. The key element of the sensor is a highly ordered nanoporous structure of anodic aluminium oxide (AAO)
integrated into a microfluidic chip combined with an optical fiber spectrophotometer. AAO was prepared by
electrochemical anodization of aluminium using 0.3 M oxalic acid. The structural and geometrical features of the AAO
porous structures were controlled to provide optimal RIfS sensing characteristics and there sensing capabilities were
explored using two different strategies; i) detection based on the response generated by pefusion of analyte ions inside
the pores and ii) detection based on specific adsorption of analyte molecules on surface of AAO pores. The second
strategy is based on chemical modification of the AAO surface to target molecules based on specific surface binding
reactions. In this work two cases are presented, including the binding of small thiol molecules on gold-modified AAO
(Au-AAO) and binding of larger targets such as circulating tumour cells (CTC) on antibody-modified AAO. Our
preliminary results show an excellent capability of our system in the detection of different analytes using both strategies,
and confirm good potential for the development and application of interferometric label-free biosensing devices in a
wide range of biomedical applications.
The preparation of bilayer lipid membranes (BLMs) on solid surfaces is important for many studies probing various
important biological phenomena including the cell barrier properties, ion-channels, biosensing, drug discovery and
protein/ligand interactions. In this work we present new membrane platforms based on suspended BLMs on nanoporous
anodic aluminium oxide (AAO) membranes. AAO membranes were prepared by electrochemical anodisation of
aluminium foil in 0.3 M oxalic acid using a custom-built etching cell and applying voltage of 40 V, at 1oC. AAO
membranes with controlled diameter of pores from 30 - 40 nm (top of membrane) and 60 -70 nm (bottom of membrane)
were fabricated. Pore dimensions have been confirmed by scanning electron microscopy (SEM) and atomic force
microscopy (AFM). AAO membranes were chemically functionalised with 3-aminopropyltriethoxysilane (APTES).
Confirmation of the APTES attachment to the AAO membrane was achieved by means of infrared spectroscopy, X-ray
photoelectron spectroscopy and contact angle measurements. The Fourier transform infrared (FTIR) spectra of
functionalised membranes show several peaks from 2800 to 3000 cm-1 which were assigned to symmetric and
antisymmetric CH2 bands. XPS data of the membrane showed a distinct increase in C1s (285 eV), N1s (402 eV) and
Si2p (102 eV) peaks after silanisation. The water contact angle of the functionalised membrane was 80o as compared to
20o for the untreated membrane. The formation of BLMs comprising dioleoyl-phosphatidylserine (DOPS) on APTESmodified
AAO membranes was carried using the vesicle spreading technique. AFM imaging and force spectroscopy was
used to characterise the structural and nanomechanical properties of the suspended membrane. This technique also
confirmed the stability of bilayers on the nanoporous alumina support for several days. Fabricated suspended BLMs on
nanoporous AAO hold promise for the construction of biomimetic membrane architectures with embedded
Diatoms are unicellular photosynthetic algae with enormous diversity of patterns in their silica structures at the nano- to
micronscale. In this study, we present results, which support the hypothesis that silica nanoparticles are released into the
diatom culture medium. The formation of an opalescent film by the self-assembly of silica nanoparticles produced in the
growth medium of diatoms. This film was formed on the filter paper from the culture medium of a Coscinodiscus sp.
culture. A numbers of diatoms with partially opened valves were observed on the film surface under light microscopy
and SEM, which indicates that cell contents inside of diatoms had been released into the culture solution. AFM images of
produced opalescent films show ordered arrays of silica nanoparticles with different diameters depending on the colors
observed by light microscopy. The film forming silica nanoparticles are either released by the diatoms during
reproduction or after cell death. This approach provides an environmentally friendly means for fabricating silica
nanoparticles, decorative coatings and novel optical materials.
Atomic layer deposition (ALD) of SiO2 onto nanoporous alumina (PA) membranes was investigated with the aim of
adjusting the pore size and transport properties. PA membranes from commercial sources with a range of pore diameters
(20 nm, 100 nm and 200 nm) were used and modified by atomic layer deposition using tris(tert-butoxy)silanol and water
as the precursor couple. By adjusting the number of deposition cycles, the thickness of the conformal silica coating was
controlled, reducing the effective pore diameter, and subsequently changing the transport properties of the PA
membrane. Silica coated PA membranes with desired pore diameters from <5 nm to 100 nm were fabricated. In addition
to the pore size, the transport properties and selectivity of fabricated silica coated PA membranes were controlled by
chemical functionalisation using a silane with hydrophobic properties. Structural and chemical properties of modified
membranes were studied by dynamic secondary ion mass spectrometry (DSIMS) and scanning electron microscopy
(SEM). Spectrophotometric methods were used to evaluate the transport properties and selectivity of silica coated
membranes by permeation studies of hydrophobic and hydrophilic organic molecules. The resultant silica/PA
membranes with specific surface chemistry and controlled pore size are applicable for molecular separation, cell culture,
bioreactors, biosensing and drug delivery.