Natural Polymer-Polyphenol Bioadhesive Coacervate with Stable Wet Adhesion, Antibacterial Activity, and On-Demand Detachment.

Medical adhesives are emerging as an important clinical tool as adjuvants for sutures and staples in wound closure and healing and in the achievement of hemostasis. However, clinical adhesives combining cytocompatibility, as well as strong and stable adhesion in physiological conditions, are still in demand. Herein, a mussel-inspired strategy is explored to produce adhesive coacervates using tannic acid (TA) and methacrylate pullulan (PUL-MA). TA|PUL-MA coacervates mainly comprise van der Waals forces and hydrophobic interactions. The methacrylic groups in the PUL backbone increase the number of interactions in the adhesives matrix, resulting in enhanced cohesion and adhesion strength (72.7 Jm-2), compared to the non-methacrylated coacervate. The adhesive properties are kept in physiologic-mimetic solutions (72.8 Jm-2) for 72 h. The photopolymerization of TA|PUL-MA enables the on-demand detachment of the adhesive. The poor cytocompatibility associated with the use of phenolic groups is here circumvented by mixing reactive oxygen species-degrading enzyme in the adhesive coacervate. This addition does not hamper the adhesive character of the materials, nor their anti-microbial or hemostatic properties. This affordable and straightforward methodology, together with the tailorable adhesivity even in wet environments, high cytocompatibility, and anti-bacterial activity, enables foresee TA|PUL-MA as a promising ready-to-use bioadhesive for biomedical applications.

Unveiling the Assembly of Neutral Marine Polysaccharides into Electrostatic-Driven Layer-by-Layer Bioassemblies by Chemical Functionalization.

Marine-origin polysaccharides, in particular cationic and anionic ones, have been widely explored as building blocks in fully natural or hybrid electrostatic-driven Layer-by-Layer (LbL) assemblies for bioapplications. However, the low chemical versatility imparted by neutral polysaccharides has been limiting their assembly into LbL biodevices, despite their wide availability in sources such as the marine environment, easy functionality, and very appealing features for addressing multiple biomedical and biotechnological applications. In this work, we report the chemical functionalization of laminarin (LAM) and pullulan (PUL) marine polysaccharides with peptides bearing either six lysine (K6) or aspartic acid (D6) amino acids via Cu(I)-catalyzed azide-alkyne cycloaddition to synthesize positively and negatively charged polysaccharide-peptide conjugates. The successful conjugation of the peptides into the polysaccharide's backbone was confirmed by proton nuclear magnetic resonance and attenuated total reflectance Fourier-transform infrared spectroscopy, and the positive and negative charges of the LAM-K6/PUL-K6 and LAM-D6/PUL-D6 conjugates, respectively, were assessed by zeta-potential measurements. The electrostatic-driven LbL build-up of either the LAM-D6/LAM-K6 or PUL-D6/PUL-K6 multilayered thin film was monitored in situ by quartz crystal microbalance with dissipation monitoring, revealing the successful multilayered film growth and the enhanced stability of the PUL-based film. The construction of the PUL-peptide multilayered thin film was also assessed by scanning electron microscopy and its biocompatibility was demonstrated in vitro towards L929 mouse fibroblasts. The herein proposed approach could enable the inclusion of virtually any kind of small molecules in the multilayered assemblies, including bioactive moieties, and be translated into more convoluted structures of any size and geometry, thus extending the usefulness of neutral polysaccharides and opening new avenues in the biomedical field, including in controlled drug/therapeutics delivery, tissue engineering, and regenerative medicine strategies.

Assembly of High-Potency Photosensitizer-Antibody Conjugates through Application of Dendron Multiplier Technology.

Exploitation of photosensitizers as payloads for antibody-based anticancer therapeutics offers a novel alternative to the small pool of commonly utilized cytotoxins. However, existing bioconjugation methodologies are incompatible with the requirement of increased antibody loading without compromising antibody function, stability, or homogeneity. Herein, we describe the first application of dendritic multiplier groups to allow the loading of more than 4 porphyrins to a full IgG antibody in a site-specific and highly homogeneous manner. Photophysical evaluation of UV-visible absorbance and singlet oxygen quantum yields highlighted porphyrin-dendron 14 as the best candidate for bioconjugation; with subsequent bioconjugation producing a HER2-targeted therapeutic with average loading ratios of 15.4:1. In vitro evaluation of conjugate 18 demonstrated a nanomolar photocytotoxic effect in a target cell line, which overexpresses HER2, with no observed photocytotoxicity at the same concentration in a control cell line which expresses native HER2 levels, or in the absence of irradiation with visible light.

Porphyrin modified trastuzumab improves efficacy of HER2 targeted photodynamic therapy of gastric cancer.

Gastric cancer (GC) is the 3rd deadliest cancer worldwide, due to limited treatment options and late diagnosis. Human epidermal growth factor receptor-2 (HER2) is overexpressed in ∼20% of GC cases and anti-HER2 antibody trastuzumab in combination with conventional chemotherapy, is recognized as standard therapy for HER2-positive metastatic GC. This strategy improves GC patients' survival by 2-3 months, however its optimal results in breast cancer indicate that GC survival may be improved. A new photoimmunoconjugate was developed by conjugating a porphyrin with trastuzumab (Trast:Porph) for targeted photodynamic therapy in HER2-positive GC. Using mass spectrometry analysis, the lysine residues in the trastuzumab structure most prone for porphyrin conjugation were mapped. The in vitro data demonstrates that Trast:Porph specifically binds to HER2-positive cells, accumulates intracellularly, co-localizes with lysosomal marker LAMP1, and induces massive HER2-positive cell death upon cellular irradiation. The high selectivity and cytotoxicity of Trast:Porph based photoimmunotherapy is confirmed in vivo in comparison with trastuzumab alone, using nude mice xenografted with a HER2-positive GC cell line. In the setting of human disease, these data suggest that repetitive cycles of Trast:Porph photoimmunotherapy may be used as an improved treatment strategy in HER2-positive GC patients.