Margarida M. Fernandes

Tannic acid NPs – Synthesis and immobilization onto a solid surface in a one-step process and their antibacterial and anti-inflammatory properties

Tannic acid nanoparticles were synthesized from an aqueous solution without the use of stabilizers via a sonochemical process. In order to avoid the dissolution of the formed nanoparticles, the sonochemical reaction was performed in the presence of a cotton fabric: following their formation, the tannic acid nanoparticles were embedded into the cotton substrate in a one-step process. The bioactive properties of the tannic acid coated surface were examined towards the inhibition of myeloperoxidase and collagenase, two major enzymes related with inflammatory processes. In addition, the antibacterial activity of the tannic acid nanoparticles coated textiles was evaluated against Staphylococcus aureus and Pseudomonas aeruginosa.

Bacteria-responsive multilayer coatings comprising polycationic nanospheres for bacteria biofilm prevention on urinary catheters

UNLABELLED This work reports on the development of infection-preventive coatings on silicone urinary catheters that contain in their structure and release on demand antibacterial polycationic nanospheres. Polycationic aminocellulose conjugate was first sonochemically processed into nanospheres to improve its antibacterial potential compared to the bulk conjugate in solution (ACSol). Afterward the processed aminocellulose nanospheres (ACNSs) were combined with the hyaluronic acid (HA) polyanion to build a layer-by-layer construct on silicone surfaces. Although the coating deposition was more effective when HA was coupled with ACSol than with ACNSs, the ACNSs-based coatings were thicker and displayed smoother surfaces due to the embedment of intact nanospheres. The antibacterial effect of ACNSs multilayers was 40% higher compared to ACSol coatings. This fact was further translated into more effective prevention of Pseudomonas aeruginosa biofilm formation. The coatings were stable in the absence of bacteria, whereas their disassembling occurred gradually during incubation with P. aeruginosa, and thus eradicate the biofilm upon release of antibacterial agents. Only 5 bilayers of HA/ACNSs were sufficient to prevent the biofilm formation, in contrast to the 10 bilayers of ACSol required to achieve the same effect. The antibiofilm efficiency of (HA/ACNSs)10 multilayer construct built on a Foley catheter was additionally validated under dynamic conditions using a model of the catheterized bladder in which the biofilm was grown during seven days. STATEMENT OF SIGNIFICANCE Antibacterial layer-by-layer coatings were fabricated on silicone that efficiently prevents Pseudomonas aeruginosa biofilm formation during time beyond the useful lifetime of the currently employed urinary catheters in medical practice. The coatings are composed of intact, highly antibacterial polycationic nanospheres processed from aminated cellulose and bacteria-degrading glycosaminoglycan hyaluronic acid. The importance of incorporating nanoscale structures within bacteria-responsive surface coatings to impart durable antibacterial and self-defensive properties to the medical indwelling devices is highlighted.

One-step sonochemical preparation of redox-responsive nanocapsules for glutathione mediated RNA release

Efficient RNA delivery to targeted cells requires the use of stable interactive carriers that provide RNA protection during the extracellular transit and trigger release once internalised. One strategy to avoid the premature extracellular RNA drain coupled to sufficient intracellular release is the use of stimuli-responsive delivery materials exploiting as a triggering mechanism the redox gradient between the extra- and intracellular compartments. This work describes a facile route for the preparation of redox-active nanocarriers containing disulphides that combine RNA protection and delivery on demand based on intracellular glutathione (GSH) levels. A one-step sonochemical technology was employed to generate thiolated chitosan (TC) nanocapsules with a diameter between 250 and 570 nm and simultaneously load them with RNA. Their size and physiological stability were directly proportional to the extent of disulphide cross-linking, which in turn could be ruled by adjusting the processing pH and degree of chitosan thiolation. TC processing into nanocapsules showed to be advantageous in terms of RNA condensation and protection compared to the typically employed nanocomplexation. Fluorescence microscopy imaging revealed that: (i) the nanocapsules enter the human fibroblasts and migrate to the perinuclear regions within 1 h, and (ii) the cargo release may occur after the internalisation. These redox-responsive and biocompatible drug carriers demonstrated an effective (∼60%) and sustained (up to 72 h) RNA release at intracellular GSH concentrations (10 mM) in vitro, based on disulphide reduction and consequent capsule disassembly.

Escherichia coli and Pseudomonas aeruginosa eradication by nano-penicillin G

The transformation of penicillin G into nano/micro-sized spheres (nanopenicillin) using sonochemical technology was explored as a novel tool for the eradication of Gram-negative bacteria and their biofilms. Known by its effectiveness only against Gram-positive microorganisms, the penicillin G spherization boosted the inhibition of the Gram-negative Pseudomonas aeruginosa 10-fold (from 0.3 to 3.0 log-reduction) and additionally induced 1.2 log-reduction of Escherichia coli growth. The efficient penetration of the spheres within a Langmuir monolayer sustained the theory that nanopenicillin is able to cross the membrane and reach the periplasmic space in Gram-negative bacteria where they inhibit the β-lactam targets: the transferases that build the bacteria cell wall. Moreover, it considerably suppressed the growth of both bacterial biofilms on a medically relevant polystyrene surface, leaving majority of the adhered cells dead compared to the treatment with the non-processed penicillin G. Importantly, nanopenicillin was found innocuous towards human fibroblasts at the antibacterial-effective concentrations.

Biocompounds from rapeseed oil industry co-stream as active ingredients for skin care applications

Despite the great number of substances produced by the skincare industry, very few of them seem to truly have an effect on the skin. Therefore, given the social implications surrounding physical appearance, the search for new bioactive compounds to prevent or attenuate skin ageing and enhance self‐image is a priority of current research. In this context, being rich in valuable compounds, such as proteins, phenolics, lipids and vitamins, this study is focused on the potential activity of rapeseed press cake hydrolysates to be used as raw materials for skincare applications.

ACL injuries identifiable for pre-participation imagiological analysis: Risk factors

Identification of pre-participation risk factors for noncontact anterior cruciate ligament (ACL) injuries has been attracting a great deal of interest in the sports medicine and traumatology communities. Appropriate methods that enable predicting which patients could benefit from preventive strategies are most welcome. This would enable athlete-specific training and conditioning or tailored equipment in order to develop appropriate strategies to reduce incidence of injury. In order to accomplish these goals, the ideal system should be able to assess both anatomic and functional features. Complementarily, the screening method must be cost-effective and suited for widespread application. Anatomic study protocol requiring only standard X rays could answer some of such demands. Dynamic MRI/CT evaluation and electronically assisted pivot-shift evaluation can be powerful tools providing complementary information. These upcoming insights, when validated and properly combined, envision changing pre-participation knee examination in the near future. Herein different methods (validated or under research) aiming to improve the capacity to identify persons/athletes with higher risk for ACL injury are overviewed.

Strategies for Silencing Bacterial Communication

Recent advances in microbiology have revealed that bacteria are able to communicate and cooperate in a wide range of multicellular behaviors such as dispersal, foraging and biofilm formation, in a process called quorum sensing (QS). In the QS-regulated communication, bacteria produce and secrete small signaling molecules – autoinducers that are recognised by specific receptors. Gram-negative bacteria secrete acyl-homoserine lactones (AHLs) that in threshold concentrations penetrate into the cells and activate cognate intracellular AHL receptors, while gram-positive bacteria produce autoinducing peptides that are detected by the cell membrane histidine kinase receptor. However, not all bacterial communication is species specific. Bacteria also possess a receptor for the signals sent out by other bacteria species. The knowledge about how this intra- and inter-species communication occurs has been increasingly used to develop new strategies for fighting infectious diseases. This chapter summarises recent advances for silencing cell-to-cell communication as a new approach for the prevention of bacterial diseases.

Polymers in Wound Repair

Efficient dermal wound care implies providing a healing environment at the site of injury. Current repair techniques, including polymeric dressings, are able to accelerate only the healing of epidermal and partial thickness acute wounds based on maintaining the area moist. However, these are not efficient in treatment of full-thickness and chronic wounds, which lack in inborn regenerative elements and are highly prone to infections. For this reason the research interest is nowadays shifted towards functional biomaterials to tackle severe skin deteriorations by providing a beneficiary for healing pro-active and pathogen-free environment. Recent advances in molecular biology and materials science together with better understanding of wound pathophysiology allowed for designing of new wound care approaches that rely on biochemical stimuli to promote wound closure. Biopolymers that couple intrinsic antimicrobial and wound repair properties with hydrophilicity appear as suitable dressing platforms. These can be further upgraded using various bio-entities (therapeutic molecules, cells) with the ability to address specific targets in the biochemical environment of wounds in order to stimulate the healing process. This chapter summarises the abundant experimental and clinical data on polymers in advanced wound dressings, scaffolds for dermal regeneration and platforms for drug delivery.

Bottom-up Layer-by-Layer Assembling of Antibacterial Freestanding Nanobiocomposite Films

In this study, freestanding nanobiocomposite films were obtained by the sequential deposition of biopolymer-capped silver nanoparticles (AgNPs) and hyaluronic acid (HA). At first, dispersions of AgNPs decorated with chitosan (CS) or aminocellulose (AC) were synthesized by applying high intensity ultrasound. These polycationic nanoentities were layer-by-layer assembled with the HA polyanion to generate stable 3D supramolecular constructs, where the biopolymer-capped AgNPs play the dual role of active agent and structural element. SEM images of the assemblies revealed gradual increase of thickness with the number of deposited bilayers. The composites of ≥50 bilayers were safe to human cells and demonstrated 100% antibacterial activity against Staphylococcus aureus and Escherichia coli. Moreover, the films containing CSAgNPs brought about the total prevention of biofilm formation reducing the cells surface adherence by up to 6 logs. Such nanobiocomposites could serve as an effective barrier to control bacterial growth on injured skin, burns, and chronic wounds.