Engineering of Bioresorbable Polymers for Tissue Engineering and Drug Delivery Applications.

Herein, the recent advances in the development of resorbable polymeric-based biomaterials, their geometrical forms, resorption mechanisms, and their capabilities in various biomedical applications are critically reviewed. A comprehensive discussion of the engineering approaches for the fabrication of polymeric resorbable scaffolds for tissue engineering, drug delivery, surgical, cardiological, aesthetical, dental and cardiovascular applications, are also explained. Furthermore, to understand the internal structures of resorbable scaffolds, representative studies of their evaluation by medical imaging techniques, e.g., cardiac computer tomography, are succinctly highlighted. This approach provides crucial clinical insights which help to improve the materials' suitable and viable characteristics for them to meet the highly restrictive medical requirements. Finally, the aspects of the legal regulations and the associated challenges in translating research into desirable clinical and marketable materials of polymeric-based formulations, are presented.

A technique for improving dispersion within polymer-glass composites using polymer precipitation.

Particulate reinforcement of polymeric matrices is a powerful technique for tailoring the mechanical and degradation properties of bioresorbable implant materials. Dispersion of inorganic particles is critical to achieving optimal properties, however established techniques such as twin-screw extrusion or solvent casting can have significant drawbacks including excessive thermal degradation or particle agglomeration. We present a facile method for production of polymer-inorganic composites that reduces the time at elevated temperature and the time available for particle agglomeration. Glass slurry was added to a dissolved PLLA solution, and ethanol was added to precipitate polymer onto the glass particles. Characterisation of parts formed by subsequent micro-injection moulding of composite precipitate revealed a significant reduction in agglomeration, with d0.9 reduced from 170 to 43 µm. This drastically improved the ductility (ɛB) from 7% to 120%, without loss of strength or stiffness. The method is versatile and applicable to a wide range of polymer and filler materials.

Femtosecond lasers for high-precision orthopedic surgery.

Laser micromachining with ultrashort pulses has shown great promise for clean, safe surgical treatment of bone tissue. However, comparisons of performance and development of "best practice" have been hampered by the difficulty of comparing results across a wide variety of experimental approaches and under surgically irrelevant conditions (e.g., dried, dead bone). Using a femtosecond (fs) pulsed laser system (τ = 140 fs, repetition rate = 1 kHz, λ = 800 nm), a comprehensive study of femtosecond laser microsurgery using the standard metrics of laser micromachining (ablation threshold, incubation effects, ablation rates, effect of focal point depth within the material and heat affected zone (HAZ)) was conducted on live, freshly harvested bovine and ovine cortical bone. Three important points of optimism for future implementation in the surgical theatre were identified: (1) the removal of material is relatively insensitive to the focal point depth within the material, removing the need for extreme depth precision for excellent performance; (2) femtosecond laser ablation of fresh bone demonstrates very little incubation effect, such that multiple passes of the laser over the same region of bone removes the same amount of material; and (3) the complete absence of collateral damage, heat- or shock-induced, on both the macro- and microscopic scales can be achieved readily, within a broad parameter range. Taken together, these results indicate a handheld or robotic deployed fiber laser platform for femtosecond laser microsurgery is a very viable prospect.

Measuring the ablation threshold fluence in femtosecond laser micromachining with vortex and Bessel pulses.

Femtosecond laser micromachining holds significant promise for advanced manufacturing, however uptake has been limited by the low processing speed. Altering the beam shape from its typical Gaussian profile has been attempted to improve efficiency, however virtually all reliable methods for quantifying the efficiency assume a Gaussian beam shape. Here, we describe an approach for quantifying the ablation threshold fluence - the key parameter for comparing efficiency - suitable for weakly focused non-Gaussian beams. We successfully demonstrate this method for Bessel and vortex beams, finding that the ablation threshold depends not just on the material, but the beam shape as well.

Gold-sputtered Blu-ray discs: simple and inexpensive SERS substrates for sensitive detection of melamine.

Nanostructured gold substrates provide chemically stable, signal-enhancing substrates for the sensitive detection of a variety of compounds through surface-enhanced Raman spectroscopy (SERS). Recent developments in advanced fabrication methods have enabled the manufacture of SERS substrates with repeatable surface nanostructures that provide reproducible quantitative analysis, historically a weakness of the SERS technique. Here, we describe the novel use of gold-sputtered Blu-ray disc surfaces as SERS substrates. The unique surface features and composition of the Blu-ray disc recording surface lead to the formation of gold nano-islands and nanogaps following simple gold sputtering, without any background peaks from the substrate. The SERS performance of this substrate is strong and reproducible with an enhancement factor (EF) of 10(3) for melamine. A limit of detection (LOD) for this compound of 70 ppb and average reproducibility of ±12 % were achieved. Gold-sputtered Blu-ray discs thus offer an excellent alternative to more exotic gold SERS substrates prepared by advanced, time-consuming and expensive methods. Graphical abstract AFM 3D images of 1-µm(2) sections of uncoated and gold-sputtered recordable Blu-ray disc (BD-R) surfaces and the SERS signal obtained on the gold-sputtered surface for a 1000 ppm aqueous solution of melamine.

Topologically ordered magnesium-biopolymer hybrid composite structures.

Magnesium and its alloys are intriguing as possible biodegradable biomaterials due to their unique combination of biodegradability and high specific mechanical properties. However, uncontrolled biodegradation of magnesium during implantation remains a major challenge in spite of the use of alloying and protective coatings. In this study, a hybrid composite structure of magnesium metal and a biopolymer was fabricated as an alternative approach to control the corrosion rate of magnesium. A multistep process that combines metal foam production and injection molding was developed to create a hybrid composite structure that is topologically ordered in all three dimensions. Preliminary investigations of the mechanical properties and corrosion behavior exhibited by the hybrid Mg-polymer composite structures suggest a new potential approach to the development of Mg-based biomedical devices.