Biocompatible Polymer Films Research Articles

Development of pH‐Sensitive Film for Detection of Implant Infection via Ultrasound Luminescent Chemical Imaging

AbstractA new hybrid ultrasound luminescent chemical imaging technique is described along with a pH sensor to image chemical concentrations at the surface of implanted medical devices. The purpose is to detect and study local biochemistry during infection. The sensor comprises a mechanoluminescent film (SrAl2O4:Eu, Dy microphosphors embedded in a biocompatible polymer film) and a pH indicator dye. A focused ultrasound beam generates green luminescence at the ultrasound focal point. By pulsing the ultrasound ON and OFF, the modulated luminescence can be distinguished from persistent luminescence, for high spatial resolution imaging. A red fluorescent dye and the pH indicator dye bromothymol blue are added to the coating to modulate the red‐light transmittance via pH dependent absorbance. Acidosis is observed as an increase in red luminescence intensity in spectroscopy and imaging. The films are sensitive to biologically relevant changes in pH (6.0–8.0) and can be imaged through optically scattering media to mimic tissue. The images have a knife edge spatial resolution of ≈3 mm through optically scattering phantoms, limited by the focused ultrasound spot size. This novel technique may permit the elucidation of implant infection at the implant surface and can be further developed for the measurement of other relevant chemical species in the future.

Biocompatible Film‐Coating of Magnetic Soft Robots for Mucoadhesive Locomotion (Adv. Mater. Technol. 12/2023)

Magnetic Soft Robots In article number 2201813, Venkatsubramanian Kalpathy Venkiteswaran and co-workers develop a biocompatible soft polymer film for coating the outer surface of a soft robot which can be controlled using magnetic fields. The Chitosan-Glycerol film endows the robot with ability of locomotion on confined 3D surfaces through the formation of hydrogen bonds with mucus-covered biological surfaces.

Thermal Analysis of Parylene Thin Films for Barrier Layer Applications.

Biocompatible polymer films demonstrating excellent thermal stability are highly desirable for high-temperature (>250 °C) applications, especially in the bioelectronic encapsulation domain. Parylene, as an organic thin film, is a well-established polymer material exhibiting excellent barrier properties and is often the material of choice for biomedical applications. This work investigated the thermal impact on the bulk properties of four types of parylene films: parylene N, C, VT4, and AF4. The films, deposited using the standard Gorham process, were analyzed at varying annealing temperatures from room temperature up to 450 °C. Thermal properties were identified by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) methods, while X-ray diffraction (XRD) analysis showed the effect of high-temperature exposure on the structural properties. In addition to thermal and structural analysis, the barrier properties were measured through the helium transmission rate (HTR) and the water vapor transmission rate (WVTR). Fluorinated parylene films were confirmed to be exceptional materials for high-temperature applications. Parylene AF4 film, 25um thick, demonstrated excellent barrier performance after 300 °C exposure, with an HTR and a WVTR of 12.18 × 103 cm3 (STP) m−2 day−1 atm−1 and 6.6 g m−2 day−1, respectively.

Starch-Mucilage Composite Films: An Inclusive on Physicochemical and Biological Perspective.

In recent years, scientists have focused on research to replace petroleum-based components plastics, in an eco-friendly and cost-effective manner, with plant-derived biopolymers offering suitable mechanical properties. Moreover, due to high environmental pollution, global warming, and the foreseen shortage of oil supplies, the quest for the formulation of biobased, non-toxic, biocompatible, and biodegradable polymer films is still emerging. Several biopolymers from varied natural resources such as starch, cellulose, gums, agar, milk, cereal, and legume proteins have been used as eco-friendly packaging materials for the substitute of non-biodegradable petroleum-based plastic-based packaging materials. Among all biopolymers, starch is an edible carbohydrate complex, composed of a linear polymer, amylose, and amylopectin. They have usually been considered as a favorite choice of material for food packaging applications due to their excellent forming ability, low cost, and environmental compatibility. Although the film prepared from bio-polymer materials improves the shelf life of commodities by protecting them against interior and exterior factors, suitable barrier properties are impossible to attain with single polymeric packaging material. Therefore, the properties of edible films can be modified based on the hydrophobic–hydrophilic qualities of biomolecules. Certain chemical modifications of starch have been performed; however, the chemical residues may impart toxicity in the food commodity. Therefore, in such cases, several plant-derived polymeric combinations could be used as an effective binary blend of the polymer to improve the mechanical and barrier properties of packaging film. Recently, scientists have shown their great interest in underutilized plant-derived mucilage to synthesize biodegradable packaging material with desirable properties. Mucilage has a great potential to produce a stable polymeric network that confines starch granules that delay the release of amylose, improving the mechanical property of films. Therefore, the proposed review article is emphasized on the utilization of a blend of source and plant-derived mucilage for the synthesis of biodegradable packaging film. Herein, the synthesis process, characterization, mechanical properties, functional properties, and application of starch and mucilage-based film are discussed in detail.

On-Site Longitudinal Monitoring of Crop Health Using Vapor-Printed Polymer Tattoos

Emergent wearable health-monitoring devices use a tissue-adhered electrode as their sensing element, which is typically created by applying a preformed polymer, nanoparticle/nanowire or carbon material film onto the outer surface of an organism. However, the surfaces of organisms display staggeringly diverse microscale features, and the complex biochemical, mechanical and transport phenomena that operate at the interface between such microstructured living tissue and a man-made device ultimately control the performance and longevity of tissue-adhered electrodes. Contemporary stick-and-play devices, such as smart patches and press-on buttons, are often susceptible to device delamination from the surface of living organisms and, often, perturb air/water/nutrient transport at the biointerface, reducing long-term viability. We demonstrate a new paradigm for vapor printing biocompatible polymer films directly onto a living organism, creating conformal and long-lasting electrodes that allow for long-term health monitoring using bioimpedance measurements. This approach enables on-site and longitudinal monitoring of otherwise hard to track abiotic stressors, such as ozone damage, even at low exposure levels. Oxidative damage produces a unique change in the high-frequency (>104 Hz) impedance and phase signals of leaves, which is not replicated by other abiotic stressors, such as drought. The polymer tattoos are resilient against ozone-induced chemical degradation and persist on the leaves of fruiting plants, thus allowing for frequent and long-term monitoring of cellular ozone damage in economically important crops, such as grapes and apples.

Development of a biocompatible, biodeshipple polymer for medicine and agriculture, able to long-term extract of bioactive substances

A team of authors developed a technology for producing biocompatible biodegradable polymer films based on high-molecular polylactide with the properties necessary for medical and agricultural use. A technology has been developed for the inclusion of active substances (gentamicin sulfate, lincomycin hydrochloride, cefotaxime) into films of high-molecular polylactide. The rate of release of active substances from polylactide can vary with time as a decaying exponent, as well as a function close to linear. The process of release of active substances is significantly affected by the pH of the surrounding film of the solution. It was found that the dynamics of release of active substances from biocompatible biodegradable polymer films created on the basis of high-molecular polylactide depends on the properties of the substance immobilized in the film, the technology of the film and the conditions under which the extraction is carried out. The technical parameters of biocompatible biodegradable polymer films based on high-molecular polylactide are quite suitable for the manufacture of coatings of stents and prostheses with prolonged and controlled release of drugs into the surrounding tissues, as well as for use in agriculture to increase the safety of the harvest.

Development of a Biocompatible and Biodegradable Polymer Capable of Long-Term Release of Biologically Active Substances for Medicine and Agriculture

A process was developed for producing biocompatible and biodegradable polymer films based on high-molecular-weight polylactide with properties necessary for medical and agricultural applications. A method was devised for the inclusion of active substances (gentamicin sulfate, lincomycin hydrochloride, or cefotaxime) into high-molecular-weight polylactide films. The rate of release of active substances from polylactide can vary with time according to a decaying exponential law or nearly linearly. The release of active substances is significantly affected by pH of the solution surrounding the film. It was found that the dynamics of release of active substances from biocompatible biodegradable polymer films based on high-molecular-weight polylactide depends on the properties of the immobilized substance, the film preparation method, and the conditions of extraction. The biocompatible biodegradable polymer films based on high-molecular-weight polylactide are quite suitable for the manufacture of coatings for stents and prostheses with prolonged and controlled drug release into the surrounding tissues and for agricultural applications to improve crop preservation.

Gallium-doped titania nanotubes elicit anti-bacterial efficacy in vivo against Escherichia coli and Staphylococcus aureus biofilm

In this work, the modification of titanium surface with TiO2 nano-tubes (TNTs), and a solvent casting of biocompatible polymer (poly-DL-lactic acid) film combines gallium (III), as a factor of anti-inflammatory and bone resorption inhibitors, was assessed in the spinal infection rat model. Under in vitro condition, it is found that S. aureus and E. coli can attach and competitively survive on the TiO2 nano-tube surface and form the mixed bacteria biofilm. By contrasting the in vivo implantation of Cp Ti, TNTs and Ga-Cp Ti scaffolds, Ga-doped TNTs showed distinct and excellent anti-bacterial property and reduced inflammation and favorable compatibility with osteoblasts, which reveal a large potential of exploiting and modifying the multi-biofunction of implantable biomaterials. The described in vivo work expands the fundamental understanding of the advantages of gallium (III) and titania nano-array on antiresorptive and antimicrobial properties and the designing strategy of the composite coating is broadly applicable to a wide range of multifunctional biomaterials.

Mechanically robust antireflective coatings

Mechanical strength is an essential parameter that influences and limits the lifetime performance of antireflective (AR) coatings in optical devices. Specifically, amphiphobic AR coatings with reduced reflectance are of great significance as they considerably enlarge the range of fundamental applications. Herein, we describe the design and fabrication of amphiphobic AR coatings with reduced reflectance and enhanced mechanical resilience. Introducing a thin polytetrafluoroethylene (PTFE) layer on top of the bilayer SiO2 coating via vapor deposition method makes it highly liquid repellent. We achieved reduced reflectance (< 1%) over the entire visible wavelength range, as well as tunability according to the desired wavelength region. The fabricated film showed better thermal stability (up to 300 °C) with stable AR efficiency, when an ultrathin dense coat of Al2O3 was deposited via atomic layer deposition (ALD) on the polymer-based bilayer SiO2 antireflective coating (P-BSAR). The experimental results prove that the omnidirectional AR coating in this study exhibits multifunctional properties and should be suitable for the production of protective optical equipment and biocompatible polymer films for the displays of portable electronic devices.

Ordered honeycomb biocompatible polymer films via a one-step solution-immersion phase separation used as a scaffold for cell cultures

Ordered porous biocompatible polymer films with controllable pore dimensions have vast application potential in biotechnology. In this article, a large-scale, ordered honeycomb biocompatible poly(lactic acid) film that is fabricated using a simple, scalable solution-immersion phase separation method is demonstrated. The entire preparation process is conducted in normal air without additional humidity or surfactants required. Notably, methanol, which is purposely employed to form a ternary polymer-solvent-nonsolvent solution, is critical because it not only induces phase separation and guarantees a highly ordered structure but it also assists in effectively controlling the surface morphology of the structured film. The ordered honeycomb poly(lactic acid) film produced using this approach demonstrates good adhesion and proliferation of NIH3T3 cells as evidence for use in future biomedical applications.

Direct photo-patterning on anthracene containing polymer for guiding stem cell adhesion.

BackgroundVarious micropatterned surfaces capable of guiding the selective adhesion of biomolecules such as proteins and cells are of great interests in biosensor, diagnostics, drug screening, and tissue engineering. In this study, we described a simple photo-patterning method to prepare micro-patterned films for stem cell patterning using anthracene containing polymers (PMAn). This micro patterned polymer film was prepared by the facile photo-reaction of anthracene units in polymer backbone structure.ResultsThe UV irradiation of PMAn through a photomask resulted in the quenching of fluorescent intensity as well as the changes in surface wettability from hydrophobic to hydrophilic surface. As a result, UV exposed regions of PMAn film show lower fluorescent intensity as well as higher proliferation rate of mesenchymal stem cells (MSCs) than unexposed region of PMAn film. Furthermore, the selective MSC attachment was clearly observed in the UV exposed regions of PMAn film.ConclusionWe developed a simple cell patterning method with a fluorescent, biocompatible, and patternable polymer film containing anthracene units. This method provides a facile stem cell patterning method and could be extended to various patterning of biomaterials without labor-intensive preparation and no pre-treatment for complex interactions of cell-microenvironment.

Polymer–gold nanoparticle composite films for topical application: Evaluation of physical properties and antibacterial activity

The biocompatible polymer films show potential as an alternative to gels and patches used for topical delivery of therapeutics and cosmetics. The physical strength and antimicrobial activity of polymer films are important attributes for their topical applicability. Here, we have investigated the physical properties and antibacterial activity of six commonly used film forming polymers before and after formation of nanocomposites with gold nanoparticles (AuNP). The blank and AuNP loaded polymer films were prepared by solvent casting method and characterized for thickness, tensile strength, burst strength, skin adhesion strength, degree of swelling, and porosity. The antibacterial activity of the composite films was evaluated by zone‐of‐inhibition and spectrophotometric growth inhibition method against Staphylococcus aureus and Escherichia coli. The physical characterization showed that chitosan films casted using 1.5% w/w resulted in 76 MPa of tensile strength, while zein films required 40% w/w to show 23 MPa of tensile strength. The AuNP (250 μM; 35 nm) loaded polymer films showed significantly (p &lt; 0.05) greater burst strength and skin adhesion strength compared with respective blank films. Among the polymers tested, only blank films of chitosan and zein showed antibacterial activity. On the other hand, all the AuNP loaded polymer films showed significantly (p &lt; 0.05) greater antibacterial activity. The AuNP loaded chitosan film showed E. coli growth inhibition similar to tetracycline. Taken together, chitosan‐ and zein‐AuNP nanocomposite films showed better physical properties and antibacterial activity. POLYM. COMPOS., 38:2829–2840, 2017. © 2015 Society of Plastics Engineers

Novel use of superdisintegrants as viscosity enhancing agents in biocompatible polymer films containing griseofulvin nanoparticles

The advantages of using superdisintegrants, sodium starch glycolate (SSG), croscarmellose sodium (CCS) and crospovidone (CP) over traditional high molecular weight (MW) viscosity enhancing agents, guar gum (GG), xanthan gum (XG), pectin and high MW HPMC are examined for improving drug content uniformity without compromising dissolution of films containing nanoparticles of griseofulvin (GF), used as a model poorly water-soluble drug. Films were fabricated by preparing low MW HPMC solutions to which a fixed amount of viscosity enhancing agents was added and mixed with GF nanosuspensions produced via wet milling, followed by casting and drying. The addition of superdisintegrants and high MW HPMC led to an increase in viscosity of precursor suspensions without GF particle aggregation, and hence excellent drug content uniformity along with retention of the high surface area of the GF nanoparticles in dried films. In contrast, the addition of XG and pectin resulted in aggregation of GF particles in suspensions, leading to poor content uniformity and incomplete recovery of GF nanoparticles upon redispersion of dried films. In spite of their high precursor viscosity, the films containing superdisintegrants did not lead to increased mechanical strength and demonstrated fast drug release, suggesting faster matrix erosion. In contrast, films with high MW polymers (GG, XG, and pectin and high MW HPMC) had increased mechanical strength and their subsequent slow erosion/disintegration along with longer hydration times resulted in significant delay of drug release, which was found to be directly proportional to their MW. These results demonstrate novel use for superdisintegrants as economical and superior alternative to traditional viscosity enhancing agents in forming drug laden biocompatible polymer films.

MO‐FG‐BRA‐04: Leveraging the Abscopal Effect Via New Design Radiotherapy Biomaterials Loaded with Immune Checkpoint Inhibitors

Purpose:Studies show that stereotactic body radiation therapy (SBRT) of a primary tumor in combination with immune checkpoint inhibitors (ICI) could Result in an immune‐mediated regression of metastasis outside the radiation field, a phenomenon known as abscopal effect. However toxicities due to repeated systematic administration of ICI have been shown to be a major obstacle in clinical trials. Towards overcoming these toxicity limitations, we investigate a potential new approach whereby the ICI are administered via sustained in‐situ release from radiotherapy (RT) biomaterials (e.g. fiducials) coated with a polymer containing the ICI.Methods:New design RT biomaterials were prepared by coating commercially available spacers/fiducials with a biocompatible polymer (PLGA) film containing fluorescent nanoparticles of size needed to load the ICI. The release of the nanoparticles was investigated in‐vitro. Meanwhile, an experimentally determined in‐ vivo nanoparticle diffusion coefficient was employed in analytic calculations based on Fick's second law to estimate the time for achieving the concentrations of ICI in the tumor draining lymph node (TDLN) that are needed to engender the abscopal effect during SBRT. The ICI investigated here was anti‐CTLA‐4 antibody (ipilimumab) at approved FDA concentrations.Results:Our in ‐vitro study results showed that RT biomaterials could be designed to achieve burst release of nanoparticles within one day. Meanwhile, our calculations indicate that for a 2 to 4 cm tumor it would take 4–22 days, respectively, following burst release, for the required concentration of ICI nanoparticles to accumulate in the TDLN during SBRT.Conclusion:Current investigations combining RT and immunotherapy involve repeated intravenous administration of ICI leading to significant systemic toxicities. Our preliminary results highlight a potential new approach for sustained in‐situ release of the ICI from new design RT biomaterials. These results provide impetus for more studies to leverage the powerful abscopal effect, while minimizing systemic toxicities through the new approach.

Control of Heterogeneous Nucleation via Rationally Designed Biocompatible Polymer Surfaces with Nanoscale Features

Direct control of nucleation in a crystallization process is difficult to achieve but offers many potential benefits to the food, chemicals, and pharmaceutical industries. We demonstrate a rational approach for designing and fabricating biocompatible polymer films that can drastically enhance nucleation rates and enable polymorph selection of small-molecule compounds. The core design philosophy was to calculate angles between major crystal faces and determine suitable substrate geometry to use for enhancing heterogeneous nucleation. Aspirin and indomethacin were used as model compounds; poly(vinyl alcohol) (PVA) with no additional chemical modification was made into films and imprinted with nanoscale features. Nucleation induction time experiments showed that using PVA films significantly reduced the nucleation induction time at a fixed supersaturation due to favorable chemical interactions and could be further reduced when the angles of the nano-indentations on the substrate matched the angles between di...

Fast drying of biocompatible polymer films loaded with poorly water-soluble drug nano-particles via low temperature forced convection

Fast drying of nano-drug particle laden strip-films formed using water-soluble biocompatible polymers via forced convection is investigated in order to form films having uniform drug distribution and fast dissolution. Films were produced by casting and drying a mixture of poorly water soluble griseofulvin (GF) nanosuspensions produced via media milling with aqueous hydroxypropyl methylcellulose (HPMC E15LV) solutions containing glycerin as a plasticizer. The effects of convective drying parameters, temperature and air velocity, and film-precursor viscosity on film properties were investigated. Two major drying regimes, a constant rate period as a function of the drying conditions, followed by a single slower falling rate period, were observed. Films dried in an hour or less without any irreversible aggregation of GF nanoparticles with low residual water content. Near-infrared chemical imaging (NIR-CI) and the content uniformity analysis indicated a better drug particle distribution when higher viscosity film-precursors were used. Powder X-ray diffraction showed that the GF in the films retained crystallinity and the polymorphic form. USP IV dissolution tests showed immediate release (~20 min) of GF. Overall, the films fabricated from polymer-based suspensions at higher viscosity dried at different conditions exhibited similar mechanical properties, improved drug content uniformity, and achieved fast drug dissolution.

Bridging the Bio-Electronic Interface with Biofabrication

Advancements in lab-on-a-chip technology promise to revolutionize both research and medicine through lower costs, better sensitivity, portability, and higher throughput. The incorporation of biological components onto biological microelectromechanical systems (bioMEMS) has shown great potential for achieving these goals. Microfabricated electronic chips allow for micrometer-scale features as well as an electrical connection for sensing and actuation. Functional biological components give the system the capacity for specific detection of analytes, enzymatic functions, and whole-cell capabilities. Standard microfabrication processes and bio-analytical techniques have been successfully utilized for decades in the computer and biological industries, respectively. Their combination and interfacing in a lab-on-a-chip environment, however, brings forth new challenges. There is a call for techniques that can build an interface between the electrode and biological component that is mild and is easy to fabricate and pattern. Biofabrication, described here, is one such approach that has shown great promise for its easy-to-assemble incorporation of biological components with versatility in the on-chip functions that are enabled. Biofabrication uses biological materials and biological mechanisms (self-assembly, enzymatic assembly) for bottom-up hierarchical assembly. While our labs have demonstrated these concepts in many formats, here we demonstrate the assembly process based on electrodeposition followed by multiple applications of signal-based interactions. The assembly process consists of the electrodeposition of biocompatible stimuli-responsive polymer films on electrodes and their subsequent functionalization with biological components such as DNA, enzymes, or live cells. Electrodeposition takes advantage of the pH gradient created at the surface of a biased electrode from the electrolysis of water. Chitosan and alginate are stimuli-responsive biological polymers that can be triggered to self-assemble into hydrogel films in response to imposed electrical signals. The thickness of these hydrogels is determined by the extent to which the pH gradient extends from the electrode. This can be modified using varying current densities and deposition times. This protocol will describe how chitosan films are deposited and functionalized by covalently attaching biological components to the abundant primary amine groups present on the film through either enzymatic or electrochemical methods. Alginate films and their entrapment of live cells will also be addressed. Finally, the utility of biofabrication is demonstrated through examples of signal-based interaction, including chemical-to-electrical, cell-to-cell, and also enzyme-to-cell signal transmission. Both the electrodeposition and functionalization can be performed under near-physiological conditions without the need for reagents and thus spare labile biological components from harsh conditions. Additionally, both chitosan and alginate have long been used for biologically-relevant purposes. Overall, biofabrication, a rapid technique that can be simply performed on a benchtop, can be used for creating micron scale patterns of functional biological components on electrodes and can be used for a variety of lab-on-a-chip applications.

Bridging the Bio-Electronic Interface with Biofabrication

Advancements in lab-on-a-chip technology promise to revolutionize both research and medicine through lower costs, better sensitivity, portability, and higher throughput. The incorporation of biological components onto biological microelectromechanical systems (bioMEMS) has shown great potential for achieving these goals. Microfabricated electronic chips allow for micrometer-scale features as well as an electrical connection for sensing and actuation. Functional biological components give the system the capacity for specific detection of analytes, enzymatic functions, and whole-cell capabilities. Standard microfabrication processes and bio-analytical techniques have been successfully utilized for decades in the computer and biological industries, respectively. Their combination and interfacing in a lab-on-a-chip environment, however, brings forth new challenges. There is a call for techniques that can build an interface between the electrode and biological component that is mild and is easy to fabricate and pattern. Biofabrication, described here, is one such approach that has shown great promise for its easy-to-assemble incorporation of biological components with versatility in the on-chip functions that are enabled. Biofabrication uses biological materials and biological mechanisms (self-assembly, enzymatic assembly) for bottom-up hierarchical assembly. While our labs have demonstrated these concepts in many formats 1,2,3, here we demonstrate the assembly process based on electrodeposition followed by multiple applications of signal-based interactions. The assembly process consists of the electrodeposition of biocompatible stimuli-responsive polymer films on electrodes and their subsequent functionalization with biological components such as DNA, enzymes, or live cells 4,5. Electrodeposition takes advantage of the pH gradient created at the surface of a biased electrode from the electrolysis of water 6,7,. Chitosan and alginate are stimuli-responsive biological polymers that can be triggered to self-assemble into hydrogel films in response to imposed electrical signals 8. The thickness of these hydrogels is determined by the extent to which the pH gradient extends from the electrode. This can be modified using varying current densities and deposition times 6,7. This protocol will describe how chitosan films are deposited and functionalized by covalently attaching biological components to the abundant primary amine groups present on the film through either enzymatic or electrochemical methods 9,10. Alginate films and their entrapment of live cells will also be addressed 11. Finally, the utility of biofabrication is demonstrated through examples of signal-based interaction, including chemical-to-electrical, cell-to-cell, and also enzyme-to-cell signal transmission. Both the electrodeposition and functionalization can be performed under near-physiological conditions without the need for reagents and thus spare labile biological components from harsh conditions. Additionally, both chitosan and alginate have long been used for biologically-relevant purposes 12,13. Overall, biofabrication, a rapid technique that can be simply performed on a benchtop, can be used for creating micron scale patterns of functional biological components on electrodes and can be used for a variety of lab-on-a-chip applications.

Prototyping chips in minutes: Direct Laser Plotting (DLP) of functional microfluidic structures

We report a fast and simple prototyping method to fabricate polymer-based microfluidic chips using Direct Laser Plotting (DLP) technique, by which various functional micro-structures can be realized within minutes, in a mask-free and out-of-cleanroom fashion. A 2D Computer-Aid-Design (CAD) software was employed to layout the required micro-structures and micro-channels, a CO2 laser plotter was then used to construct the microstructures. The desired patterns can be plotted directly on PDMS substrates and bio-compatible polymer films by manipulating the strength and density of laser pulses. With the DLP technique, chip-embedded micro-electrodes, micro-mixers and 3D microfluidic chips with 5 layers, which normally require several days of work in a cleanroom facility, can be fabricated in minutes in common laboratory. This novel method can produce microfluidic channels with average feature size of 100μm, while feature size of 50μm or smaller is achievable by making use of the interference effect from laser impulsion. In this report, we present the optimized parameters for successful fabrication of 3D microchannels, micro-mixers and microfluidic chips for protein concentration measurements (Bovine Serum Albumine (BSA) test), and a novel procedure to pattern flexible embedding electrodes on PDMS-based microfluidic chips. DLP offers a convenient and low cost alternative to conventional microfluidic channel fabrication technique which relies on complicated and hazardous soft lithography process.

Biocompatible polymer coating of titania nanotube arrays for improved drug elution and osteoblast adhesion

Bacterial infection, extensive inflammation and poor osseointegration have been identified as the major reasons for [early] orthopaedic implant failures based on titanium. Creating implants with drug-eluting properties to locally deliver drugs is an appealing way to address some of these problems. To improve properties of titanium for orthopaedic applications, this study explored the modification of titanium surfaces with titaniananotube (TNT) arrays, and approach that combines drug delivery into bone and potentially improved bone integration. A titania layer with an array of nanotube structures (∼120nm in diameter and 50μm in length) was synthesized on titanium surfaces by electrochemical anodization and loaded with the water-insoluble anti-inflammatory drug indomethacin. A simple dip-coating process of polymer modification formed thin biocompatible polymer films over the drug-loaded TNTs to create TNTs with predictable drug release characteristics. Two biodegradable and antibacterial polymers, chitosan and poly(lactic-co-glycolic acid), were tested for their ability to extend the drug release time of TNTs and produce favourable bone cell adhesion properties. Dependent on polymer thickness, a significant improvement in the drug release characteristics was demonstrated, with reduced burst release (from 77% to >20%) and extended overall release from 4days to more than 30days. Excellent osteoblast adhesion and cell proliferation on polymer-coated TNTs compared with uncoated TNTs were also observed. These results suggest that polymer-modified implants with a TNT layer are capable of delivering a drug to a bone site over an extended period and with predictable kinetics. In addition, favourable bone cell adhesion suggests that such an implant would have good biocompatibility. The described approach is broadly applicable to a wide range of drugs and implants currently used in orthopaedic practice.