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Biocompatible nanoparticles have been increasingly used in a variety of medical applications, including photodynamic therapy. Although the impact of synthesis parameters and purification methods is reported in previous studies, it is still challenging to produce a reliable protocol for the fabrication, purification, and characterization of nanoparticles in the 200-300 nm range that are highly monodisperse for biomedical applications.We investigated the synthesis of chitosan nanoparticles in the 200-300 nm range by evaluating the chitosan to sodium tripolyphosphate (TPP) mass ratio and acetic acid concentration of the chitosan solution. Chitosan nanoparticles were also crosslinked to rose bengal and incubated with human breast cancer cells (MCF-7) to test photodynamic activity using a green laser (λ = 532 nm, power = 90 mW).We established a simple protocol to fabricate and purify biocompatible nanoparticles with the most frequent size occurring between 200 and 300 nm. This was achieved using a chitosan to TPP mass ratio of 5:1 in 1% v/v acetic acid at a pH of 5.5. The protocol involved the formation of nanoparticle coffee rings that showed the particle shape to be spherical in the first approximation. Photodynamic treatment with rose bengal-nanoparticles killed ~98% of cancer cells.A simple protocol was established to prepare and purify spherical and biocompatible chitosan nanoparticles with a peak size of ~200 nm. These have remarkable antitumor activity when coupled with photodynamic treatment.

An original wireless stimulator for peripheral nerves based on a metal loop (diameter ≈1 mm) that is powered by a transcranial magnetic stimulator (TMS) and does not require circuitry components is reported. The loop can be integrated in a chitosan scaffold that functions as a graft when applied onto transected nerves (graft‐antenna). The graft‐antenna is bonded to rat sciatic nerves by a laser without sutures; it does not migrate after implantation and is able to trigger steady compound muscle action potentials for 12 weeks (CMAP ≈1.3 mV). Eight weeks postoperatively, axon regeneration is facilitated in transected nerves that are repaired with the graft‐antenna and stimulated by the TMS for 1 h per week. The graft‐antenna is an innovative and minimally‐invasive device that functions concurrently as a wireless stimulator and adhesive scaffold for nerve repair.

The organic electrochemical transistor (OECT) with a conjugated polymer as the active material is the elementary unit of organic bioelectronic devices. Improved functionalities, such as low power c ...

Interaction of conjugated polymers with liposomes is an attractive approach that benefits from both systems' characteristics such as electroactivity and enhanced interaction with cells. Conjugated polymer-liposome complexes have been investigated for bioimaging, drug delivery, and photothermal therapy. Their fabrication has largely been achieved by multistep procedures that require first the synthesis and processing of the conjugated polymer. Here, a new one step fabrication approach is reported based on in situ polymerization of a conjugated monomer precursor around liposomes. Polyaniline (PANI) doped with phytic acid is synthesized via oxidative polymerization in the presence of 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine (DOPC) vesicles to produce a conductive aqueous suspension of Liposome-PANI complexes. PANI interacts with liposomes without disrupting the bilayer as shown using differential scanning calorimetry and fluorescence quenching studies of the hydrophobic Nile red probe. The electronic conductivity of the Liposome-PANI complexes, which stems from the doped PANI accessible on the liposome surface, is confirmed using conductive atomic force microscopy and electrochemical impedance spectroscopy. Further, short-term in vitro cell studies show that the complexes colocalize with the cell membrane without reducing cell proliferation. This study presents a novel fabrication route to conductive suspensions of conjugated polymer-liposome complexes suitable for potential applications at the biointerface.

Conjugated polymers are the material of choice for organic bioelectronic interfaces as they combine mechanical flexibility with electric and ionic conductivity. Their attractive properties are largely demonstrated in vitro, while the in vivo applications are limited to the coating of inorganic electrodes, where they are used to improve the intimate electronic contact between the device and the tissue. However, there has not been a commensurate rise in the in vivo applications of entirely organic implantable electronic devices based on conjugated polymers. To date, there is no comprehensive understanding of how these devices will interface with real biological systems. With the push toward increasingly thinner and more flexible next generation medical implants, this limitation remains a major detractor in the translation of conjugated polymers toward biological applications. This research news article examines the few reported in vivo studies and attempts to establish why there is such a dearth in the literature.

A range of chitosan–based biomaterials have recently been used to perform sutureless, laser-activated tissue repair. Laser-activation has the advantage of bonding to tissue through a non-contact, aseptic mechanism. Chitosan adhesive films have also been shown to adhere to sheep intestine strongly without any chemical modification to chitosan. In this study, we continue to investigate chitosan adhesive films and explore the impact on the tissue repair strength and tensile strength characteristics of four types of adhesive film based on chitosan with different molecular weight and degree of deacetylation. Results showed that adhesives based on chitosan with medium molecular weight achieved the highest bonding strength, tensile strength and E-modulus when compared to the other adhesives. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A novel chitosan adhesive film that incorporates the dye 'Rose Bengal' (RB) was used in conjunction with a green laser to repair transected rat median nerves in vivo. Histology and electrophysiological recording assessed the impact of the laser-adhesive technique on nerves. One week post-operatively, the sham-control group (laser-adhesive technique applied on un-transected nerves) conserved the average number and size of myelinated fibres in comparison to its contralateral side and electrophysiological recordings demonstrated no significant difference with un-operated nerves. Twelve weeks after the laser-adhesive anastomoses, nerves were in continuity with regenerated axons that crossed the anastomotic site.

Onychomycosis, a fungal infection of the finger or toenails, is predominantly caused by Trichophyton rubrum. Treatment is difficult due to high recurrence rates and problems with treatment compliance. For these reasons, alternative therapies are needed. Here we describe the photoactivation of Rose Bengal (RB) using a green laser (λ = 532 nm) at fluences of 68, 133 and 228 J/cm2, and assess its fungicidal activity on T. rubrum spore suspensions. A 140 µM RB solution was able to induce a fungicidal effect on T. rubrum when photosensitized with the fluence of 228 J/cm2. RB photosensitization using a green laser provides a potential novel treatment for T. rubrum infections. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A novel approach to induce disassembly of electroactive multilayer films fabricated by the layer by layer assembly technique is reported. Electroactive multilayer films are constructed using water soluble polythiophenes, i.e., negatively charged poly[ammonium (3-thienyl)ethoxypropanesulfonate] (SPT) and positively charged poly[3-(3′-thienyloxy)ethyltriethylammonium] (APT). “Induced” dissolution of the films in response to applied potential is investigated using a quartz crystal microbalance equipped with an electrochemical cell module (EC-QCM-D). Disassembly of the films is observed in response to three different potentials: +650, –650, and ±650 mV; however the time for dissolution varies as a function of the potential with films subject to +650 mV dissolving fully in 19 h compared to 42 h for films subject to –650 mV. These electroactive films and their controlled dissolution under applied potential represent an attractive architectural feature for bionic devices that could benefit from their conductivity and dissolution over time.

Conducting polymers (CPs) have exciting potential as scaffolds for tissue engineering, typically applied in regenerative medicine applications. In particular, the electrical properties of CPs has been shown to enhance nerve and muscle cell growth and regeneration. Hydrogels are particularly suitable candidates as scaffolds for tissue engineering because of their hydrated nature, their biocompatibility, and their tissue-like mechanical properties. This study reports the development of the fi rst single component CP hydrogel that is shown to combine both electro-properties and hydrogel characteristics. Poly(3-thiopheneacetic acid) hydrogels were fabricated by covalently crosslinking the polymer with 1,1 ′ -carbonyldiimidazole (CDI). Their swelling behavior was assessed and shown to display remarkable swelling capabilities (swelling ratios up to 850%). The mechanical properties of the networks were characterized as a function of the crosslinking density and were found to be comparable to those of muscle tissue. Hydrogels were found to be electroactive and conductive at physiological pH. Fibroblast and myoblast cells cultured on the hydrogel substrates were shown to adhere and proliferate. This is the fi rst time that the potential of a single component CP hydrogel has been demonstrated for cell growth, opening the way for the development of new tissue engineering scaffolds.

Tissue reconstruction and wound closure rely on sutures, staples and clips in current surgical procedures. These traditional devices are nonetheless unable to prevent leakage of fluids from a variety of tissue including blood vessels and dura mater. Furthermore, sutures are usually difficult to apply during minimal invasive surgery and often induce detrimental scarring that may impair healing. To overcome these disadvantages, biocompatible and biodegradable glues based on fibrin, polyethylene glycol (PEG) and cyanoacrylate have recently been used in patients to seal and repair tissue wounds. Cyanoacrylate glues create typically very strong tissue bonds but have mostly been applied externally for skin wound closure because of their residual cytotoxicity. Other adhesive biomaterials are also emerging; these glues and adhesives are usually based on proteins such as albumin and collagen or polysaccharides like chitosan; these are irradiated with coherent or non-coherent light to trigger their adhesion to tissue. These biomaterial based devices offer significant advantages over sutures, such as their sealing or repairing ability, easy application modality and delivery in situ of compounds for accelerating wound healing. This paper reviews different tissue reconstruction strategies employing adhesive biomaterials currently used in surgical and experimental procedures.

Nail fungal infections are notoriously persistent and difficult to treat which can lead to severe health impacts, particularly in the immunocompromized. Current antifungal treatments, including systemic and topical drugs, are prolonged and do not effectively provide a complete cure. Severe side effects are also associated with systemic antifungals, such as hepatotoxicity. Light treatments of onychomycosis are an emerging therapy that has localized photodynamic, photothermal or photoablative action. These treatments have shown to be an effective alternative to traditional antifungal remedies with comparable or better cure rates achieved in shorter times and without systemic side effects. This report reviews significant clinical and experimental studies in the field, highlighting mechanisms of action and major effects related to light therapy; in particular, the impact of light on fungal genetics.