Photosensitive Chitosan-Based Injectable Hydrogel Chemically Cross-Linked by Perylene Bisimide Dopamine with Robust Antioxidant and Cytotoxicity Enhancer Properties for In Vitro Photodynamic Therapy of Breast Cancer.

Here, we report the fabrication of an antioxidant photosensitizing hydrogel system based on chitosan (CS-Cy/PBI-DOPA) covalently cross-linked with perylene bisimide dopamine (PBI-DOPA) as a photosensitizer. The severe insolubility and low tumor selectivity limitations of perylene were overcome by conjugation with dopamine and then to the chitosan hydrogel. The mechanical and rheological study of CS-Cy/PBI-DOPA photodynamic antioxidant hydrogels illustrated interconnected microporous morphologies with high elasticity, swelling ability, and suitable shear-thinning behavior. Bio-friendly properties, such as biodegradability and biocompatibility, excellent singlet oxygen production abilities, and antioxidant properties were also delivered. The antioxidant effects of the hydrogels control the physiological levels of reactive oxygen species (ROS) generated by photochemical reactions in photodynamic therapy (PDT), which are responsible for oxidative damage to tumor cells while protecting normal cells and tissues from ROS damage, including blood and endothelial cells. In vitro, PDT tests of hydrogels were conducted on two human breast cancer cell lines, MDA-MB-231 and MCF-7. These hydrogels offered more than 90% cell viability in the dark and good photocytotoxicity performance with 53 and 43% cell death for MCF-7 and MDA-MB-231 cells, which confirmed their promising potential for cancer therapeutic applications.

Phospholipid lateral diffusion in the presence of cationic peptides as measured via 31P CODEX NMR.

The effects of two cationic peptides on phospholipid lateral diffusion in binary mixtures of POPC with various anionic phospholipids were measured via 31P CODEX NMR. Large unilamellar vesicles composed of POPC/POPG (70/30 mol/mol), or POPC/DOPS (70/30 mol/mol), or POPC/TOCL (85/15 mol/mol), or POPC/DOPA (50/50 mol/mol) were exposed to either polylysine (pLYS, N = 134 monomers) or KL-14 (KKLL KKAKK LLKKL), a model amphipathic helical peptide, in an amount corresponding to 80% neutralization of the anionic phospholipid charge by the cationic lysine residues. In the absence of added peptide, phospholipid lateral diffusion coefficients (all measured at 10 °C) increased with increasing reduced temperature (T-Tm). The POPC/DOPA mixture was an exception to this generalization, in that lateral diffusion for both components was far slower than any other mixture investigated, an effect attributed to intermolecular hydrogen bonding. The addition of pLYS or KL-14 decreased lateral diffusion in the POPC/DOPS LUV, but had minimal effects in the POPC/POPG LUV, indicating that ease of access of the cationic peptide residues to the anionic phospholipid groups was important. Both cationic peptides produced the opposite effect in the POPC/DOPA case, in that lateral diffusion increased significantly in their presence, with KL-14 being most effective. This latter observation was interpreted in terms of the electrostatic / H-bond model proposed by Kooijman et al. [Journal of Biological Chemistry, 282:11356-11,364, 2007] to describe the mechanism of interaction between the phosphomonoester head group of PA and the tertiary amine of lysine.

Development of Thiol-Maleimide hydrogels incorporating graphene-based nanomaterials for cancer chemo-photothermal therapy.

Nano-sized materials have been widely explored in the biomedicine field, especially due to their ability to encapsulate drugs intended to be delivered to cancer cells. However, systemically administered nanomaterials face several barriers that can hinder their tumor-homing capacity. In this way, researchers are now focusing their efforts in developing technologies that can deliver the nanoparticles directly into the tumor tissue. Particularly, hydrogels assembled using Thiol-Maleimide Michael type additions are emerging for this purpose due to their capacity to incorporate high nanoparticles' doses in a compact 3D structure as well as good chemical selectivity, biocompatibility, and straightforward preparation. Nevertheless, such hydrogels have been mostly prepared using synthetic polymers, which is not ideal due to their poor biodegradability. In this work, a novel natural polymer-based Thiol-Maleimide hydrogel was produced for application in breast cancer chemo-photothermal therapy. To obtain natural polymers compatible with this crosslinking chemistry, Hyaluronic acid was endowed with Thiol groups and deacetylated Chitosan was grafted with Maleimide groups. Parallelly, Doxorubicin loaded Dopamine-reduced graphene oxide (DOX/DOPA-rGO) was prepared for attaining Near Infrared (NIR) light responsive chemo-photothermal nanoagents. By simply mixing Hyaluronic Acid-Thiol, deacetylated Chitosan-Maleimide and DOX/DOPA-rGO, Thiol-Maleimide crosslinked hydrogels incorporating this nanomaterial could be assembled (DOX/DOPA-rGO@TMgel). When breast cancer cells were incubated with DOPA-rGO@TMgel and exposed to NIR light (photothermal therapy), their viability was reduced to about 59 %. On the other hand, DOX/DOPA-rGO@TMgel (chemotherapy) reduced cancer cells' viability to 50 %. In stark contrast, the combined action of DOX/DOPA-rGO@TMgel and NIR light decreased breast cancer cells' viability to just 21 %, highlighting its chemo-photothermal potential.

pH Effects Can Dominate Chemical Shift Perturbations in 1H,15N-HSQC NMR Spectroscopy for Studies of Small Molecule/α-Synuclein Interactions.

1H,15N-Heteronuclear Single Quantum Coherence (HSQC) NMR is a powerful technique that has been employed to characterize small-molecule interactions with intrinsically disordered monomeric α-Synuclein (aSyn). We report how solution pH can impact the interpretation of aSyn HSQC NMR spectra and demonstrate that small-molecule formulations (e.g., complexation with acidic salts) can lower sample pH and confound interpretation of drug binding and concomitant protein structural changes. Through stringent pH control, we confirm that several previously identified compounds (EGCG, Baicalin, and Dopamine (DOPA)) as well as a series of potent small-molecule inhibitors of aSyn pathology (Demeclocycline, Ro90-7501, and (±)-Bay K 8644) are capable of direct target engagement of aSyn. Previously, DOPA-aSyn interactions have been shown to elicit a dramatic chemical shift perturbation (CSP) localized to aSyn's H50 at low DOPA concentrations then expanding to aSyn's acidic C-terminal residues at increasing DOPA levels. Interestingly, this CSP profile mirrors our pH titration, where a small reduction in pH affects H50 CSP, and large pH changes induce robust C-terminal CSP. In contrast, under tightly controlled pH 5.0, DOPA induces significant CSPs observed at both ionizable and nonionizable residues. These results suggest that previous interpretations of DOPA-aSyn interactions were conflated with pH-induced CSP, highlighting the need for stringent pH control to minimize potential false-positive interpretations of ligand interactions in HSQC NMR experiments. Furthermore, DOPA's preferential interaction with aSyn under acidic pH represents a novel understanding of DOPA-aSyn interactions that may provide insight into the potential gain of toxic function of aSyn misfolding in α-synucleinopathies.

Dose evaluation of the one-year-old child in PET imaging by18F-(DOPA, FDG, FLT, FET) and68Ga-EDTA using reference voxel phantoms.

Because of more sensitive organs due to high growth rates, evaluating the absorbed dose is essential for children to prevent irreparable damage. Therefore, to this aim, a one-year-old child's whole-body effective dose and organ absorbed dose were evaluated for various PET imaging Radiopharmaceuticals such as:18F-DOPA,18F-FDG,18F-FLT,18F-FET, and68Ga-EDTA. For this aim, one-year-old child reference voxel phantoms and GATE Monte Carlo simulation were used, and the results were compared with the ICRP128 report (for stylized phantom). The highest absorbed dose was related to bladder wall (for18F-DOPA,18F-FET, and68Ga-EDTA), heart wall (for18F-FDG), and liver (for18F-FLT) between 30 organs that have been studied. Comparing the results with the ICRP128 report values for a one-year-old child show a significant difference in some organs. Comparison of the effective dose with the ICRP128 report shows a relative difference of 22%, 12.5%, 11.8%, 10.8% and 8.6% for18F-DOPA,68Ga-EDTA,18F-FDG,18F-FET,18F-FLT, respectively. In conclusion, using new one-year-old voxel phantoms could provide a better estimate of organs absorbed dose and whole-body effective dose due to its exact structure.

Pyruvate and lactate based hydrogel film inhibits UV radiation-induced skin inflammation and oxidative stress.

Solar skin damage is one of the most common diseases among outdoor workers. An important cause for the damage is the ultraviolet and infrared rays in sunlight, which are absorbed by the skin in large amounts, leading to severe skin inflammation and oxidative stress. Therefore, physical prevention by shielding the light from harmful wavelengths can be an effective method of skin protection from radiation. However, for existing skin lesions, prompt treatment is essential to avoid the aggravation of the injury and promote repair. Therefore, to improve the therapeutic effect on sun-damaged skin, we attempted to design a system with a dual purpose of eliminating toxic free radicals and modulating tissue inflammatory response. Here, we designed and synthesized a poly-acryloyl lysine (P-Ac-Lys) and polyvinyl alcohol-dihydroxyphenylalanine (PVA-DOPA) composite hydrogel (PAL@PVA-DOPA Hydrogel) loaded with lactate and pyruvate, that exhibites a good free radical scavenging activity and an excellent ability to modulate the inflammatory response. Experimental results showe that this hydrogel film could effectively reduce the UV-induced skin inflammation response, alleviate pathological damage and promote the recovery of the damaged skin.

Bioorthogonal Functionalization of Material Surfaces with Bioactive Molecules.

The functionalization of material surfaces with biologically active molecules is crucial for enabling technologies in life sciences, biotechnology, and medicine. However, achieving biocompatibility and bioorthogonality with current synthetic methods remains a challenge. We report herein a novel surface functionalization method that proceeds chemoselectively and without a free transition metal catalyst. In this method, a coating is first formed via the tyrosinase-catalyzed putative polymerization of a tetrazine-containing catecholamine (DOPA-Tet). One or more types of molecule of interest containing trans-cyclooctene are then grafted onto the coating via tetrazine ligation. The entire process proceeds under physiological conditions and is suitable for grafting bioactive molecules with diverse functions and structural complexities. Utilizing this method, we functionalized material surfaces with enzymes (alkaline phosphatase, glucose oxidase, and horseradish peroxidase), a cyclic peptide (cyclo[Arg-Gly-Asp-D-Phe-Lys], or c(RGDfK)), and an antibiotic (vancomycin). Colorimetric assays confirmed the maintenance of the biocatalytic activities of the grafted enzymes on the surface. We established the mammalian cytocompatibility of the functionalized materials with fibroblasts. Surface functionalization with c(RGDfK) showed improved fibroblast cell morphology and cytoskeletal organization. Microbiological studies with Staphylococcus aureus indicated that surfaces coated using DOPA-Tet inhibit the formation of biofilms. Vancomycin-grafted surfaces additionally display significant inhibition of planktonic S. aureus growth.

Head-to-Head Comparison Between Rabbit Sign and EANM/SNMMI Criteria for the 18F-DOPA Visual Assessment of Parkinsonian Syndromes in PET/MRI: A Multiple Expert-Based and Blinded Controlled Study.

PURPOSE: The aim of this study was to compare the diagnostic performance of the rabbit visual pattern versus the one endorsed by the EANM/SNMMI for the diagnosis of parkinsonian syndromes in PET/MRI. PATIENTS AND METHODS: The 18F-DOPA PET images of 129 consecutive patients (65 Park+ and 64 controls) with 1 year of clinical follow-up were reviewed independently by 5 experienced readers on the same imaging workstation, blinded to the final clinical diagnosis. Two visual methods were assessed independently, with several days to months of interval: the criteria endorsed by EANM/SNMMI and the "rabbit" shape of the striate assessed on 3D MIP images. The sensitivities, specificities, likelihood ratios, and predictive values of the 2 diagnostic tests were estimated simultaneously by using the "comparison of 2 binary diagnostic tests to a paired design" method. RESULTS: The estimated 95% confidence interval (CI) of sensitivities and specificities ranged from 49.4% to 76.5% and from 83.2% to 97.7%, respectively. The 95% CI estimates of positive and negative likelihood ratios ranged from 3.8 to 26.7 and from 0.26 to 0.56, respectively. The 95% CI estimates of the positive and negative predictive values ranged from 78.1% to 96.7% and from 60.3% to 81.4%, respectively. For all the parameters, no statistical difference was observed between the 2 methods (P > 0.05). The rabbit sign reduced the readers' discrepancies by 25%, while maintaining the same performance. CONCLUSIONS: The rabbit visual pattern appears at least comparable to the current EANM/SNMMI reference procedure for the assessment of parkinsonian syndromes in daily clinical practice, without the need of any image postprocessing. Further multicenter prospective studies would be of relevance to validate these findings.

Ternary Synergy of Lys, Dopa, and Phe Results in Strong Cohesion of Peptide Films.

Synergistic interactions between 3,4-dihydroxyphenylalanine (Dopa, Y*), cationic residues, and the aromatic rings have been recently highlighted as influential factors that enhance the underwater adhesion strength of mussel foot proteins and their derivatives. In this study, we report the first ever evidence of a cation-catechol-benzene ternary synergy between Y*, lysine (Lys, K), and phenylalanine (Phe, F) in adhesive peptides. We synthesized three hexapeptides containing a different combination of Y*, K, and F, i.e., (KY*)3, (KF)3, and (KY*F)2, respectively, exploring the relationship between the cohesive performance and molecular architecture of peptides. The peptide with the (KY*F)2 sequence displays the strongest underwater cohesion energy of 10.3 ± 0.3 mJ m-2 from direct nanoscale surface force measurements. Combined with molecular dynamics simulation, we demonstrated that there are more bonding interactions (including cation-π, π-π, and hydrogen bond interactions) in (KY*F)2 compared to the other two peptides. In addition, peptide (KY*F)2 still shows the strongest cohesive energies of 7.6 ± 0.7 and 3.7 ± 0.5 mJ m-2 in acidic and high-ionic strength environments, respectively, although the cohesive energy decreases compared to the value in pure water. Our results further explain the underwater cohesion mechanisms combining multiple interactions and offer insights on designing Dopa containing underwater adhesives.

A polypeptide coating for preventing biofilm on implants by inhibiting antibiotic resistance genes.

Aging population has been boosting the need for orthopedic implants. However, biofilm has been a major obstacle for orthopedic implants due to its insensitivity to antibiotics and tendency to drive antimicrobial resistance. Herein, an antibacterial polypeptide coating with excellent in vivo adhesive capacity was prepared to prevent implants from forming biofilms and inducing acquired antibiotic resistance. A peptide-based copolymer, poly[phenylalanine10-stat-lysine12]-block-3,4-dihydroxy-l-phenylalanine [Poly(Phe10-stat-Lys12)-DOPA] was modularly designed, where poly(Phe10-stat-Lys12) is antibacterial polypeptide with high antibacterial activity, and DOPA provides strong adhesion in both wet and dry microenvironments. Meanwhile, compared to traditional "graft-onto" methods, this antibacterial coating can be facilely achieved by immersing Titanium substrates into antibacterial polypeptide solution for 5 min at room temperature. The poly(Phe10-stat-Lys12)-DOPA polymer showed good antibacterial activity with minimum inhibitory concentrations against S. aureus and E. coli of 32 and 400 µg/mL, respectively. Compared to obvious antimicrobial resistance of S. aureus after continuous treatment with vancomycin, this antibacterial coating doesn't drive antimicrobial resistance upon long-term utilization. Transcriptome sequencing and qPCR tests further confirmed that the antibacterial coating was able to inhibit the expression of multiple peptide resistance factor (mprF) and lipoteichoic acid modification D-alanylation genes (dltB and dltC) that can increase the net positive charge of bacterial cell wall to induce the resistance to cationic antimicrobial peptides. In vivo experiments confirmed that this poly(Phe10-stat-Lys12)-DOPA coating can both effectively prevent biofilm formation through surface contact sterilization and avoid local and systemic infections. Overall, we proposed a facile method for preparing antibacterial orthopedic implants with longer indwelling time and without inducing antimicrobial resistance by coating a polypeptide-based polymer on the implants.

Semi-Biosynthetic Production of Surface-Binding Adhesive Antimicrobial Peptides Using Intein-Mediated Protein Ligation.

Microbial infections remain a global health concern, calling for the urgent need to implement effective prevention measures. Antimicrobial peptides (AMPs) have been extensively studied as potential antimicrobial coating agents. However, an efficient and economical method for AMP production is lacking. Here, we synthesized the direct coating adhesive AMP, NKC-DOPA5, composed of NKC, a potent AMP, and repeats of the adhesive amino acid 3,4-dihydroxyphenylalanine (DOPA) via an intein-mediated protein ligation strategy. NKC was expressed as a soluble fusion protein His-NKC-GyrA (HNG) in Escherichia coli, comprising an N-terminal 6× His-tag and a C-terminal Mxe GyrA intein. The HNG protein was efficiently produced in a 500-L fermenter, with a titer of 1.63 g/L. The NKC-thioester was released from the purified HNG fusion protein by thiol attack and subsequently ligated with chemically synthesized Cys-DOPA5. The ligated peptide His-NKC-Cys-DOPA5 was obtained at a yield of 88.7%. The purified His-NKC-Cys-DOPA5 possessed surface-binding and antimicrobial properties identical to those of the peptide obtained via solid-phase peptide synthesis. His-NKC-Cys-DOPA5 can be applied as a practical and functional antimicrobial coating to various materials, such as medical devices and home appliances.

Bio-inspired conductive adhesive based on calcium-free alginate hydrogels for bioelectronic interfaces.

Electrode impedance is one of the greatest challenges facing neural interfacing medical devices and the use of electrical stimulation-based therapies in the fields of neurology and regenerative medicine. Maximizing contact between electronics and tissue would allow for more accurate recordings of neural activity and to stimulate with less power in implantable devices as electric signals could be more precisely transferred by a stable interfacial area. Neural environments, inherently wet and ion-rich, present a unique challenge for traditional conductive adhesives. As such, we look to marine mussels that use a 3,4-dihydroxyphenyl-L-analine (DOPA)-containing proteinaceous excretion to adhere to a variety of substrates for inspiration. By functionalizing alginate, which is an abundantly available natural polymer, with the catechol residues DOPA contains, we developed a hydrogel-based matrix to which carbon-based nanofiller was added to render it conductive. The synthesized product had adhesive energy within the range of previously reported mussel-based polymers, good electrical properties and was not cytotoxic to brain derived neural precursor cells.

Reduced Elastin Fibers and Melanocyte Loss in Vitiliginous Skin Are Restored after Repigmentation by Phototherapy and/or Autologous Minigraft Transplantation.

Vitiligo is a hypopigmentation disease characterized by melanocyte death in the human epidermis. However, the mechanism of vitiligo development and repigmentation is largely unknown. Dermal fiber components might play an important role in vitiligo development and repigmentation. Indeed, our preliminary study demonstrated that elastin fibers were decreased in vitiliginous skin, suggesting that the elastin fiber is one of the factors involved in vitiligo development and repigmentation. To confirm our hypothesis, we investigated whether elastin fibers can be restored after treatment using phototherapy and/or autologous skin transplantation. Punch biopsies from 14 patients of stable nonsegmental vitiligo vulgaris were collected from nonlesional, lesional, and repigmented skin, and processed to dopa and combined dopa-premelanin reactions. Melanocytes positive to the dopa reaction and melanoblasts/melanocytes positive to the combined dopa-premelanin reaction were surveyed. Moreover, elastin fibers were detected by Victoria blue staining. Numerous melanocytes and melanoblasts were observed in the epidermis of repigmented skin after the treatment. Moreover, in the dermis of repigmented skin, elastin fibers were completely recovered or even upregulated. These results suggest that melanocyte loss in the vitiliginous skin, as well as melanocyte differentiation in repigmented skin, may be at least in part regulated by elastin fibers in the dermis.

Zoledronic Acid Implant Coating Results in Local Medullary Bone Growth.

Osteoarthritis (OA) can necessitate surgical interventions to restore the function of the joint in severe cases. Joint replacement surgery is one of the procedures implemented to replace the damaged joint with prosthetic implants in severe cases of OA. However, after successful implantation, a fraction of OA patients still require revision surgery due to aseptic prosthetic loosening. Insufficient osseointegration is one of the factors that contribute to such loosening of the bone implant, which is commonly made from titanium-based materials. Zoledronic acid (ZA), a potent bisphosphonate agent, has been previously shown to enhance osseointegration of titanium implants. Herein, we fabricated ZA/Ca composites using a reverse microemulsion method and coated them with 1,2-dioleoyl-sn-glycero-3-phosphate monosodium salt (DOPA) to form ZA/Ca/DOPA composites. Titanium alloy screws were subsequently dip-coated with a suspension of the ZA/Ca/DOPA composites and poly(lactic-co-glycolic) acid (PLGA) in chloroform to yield Za/PLGA-coated screws. The coated screws exhibited a biphasic in vitro release profile with an initial burst release within 48 h, followed by a sustained release over 1 month. To assess their performance in vivo, the Za/PLGA screws were then implanted into the tibiae of Sprague-Dawley rats. After 8 weeks, microCT imaging showed new bone growth along the medullary cavity around the implant site, supporting the local release of ZA to enhance bone growth around the implant. Histological staining further confirmed the presence of new mineralized medullary bone growth resembling the cortical bone. Such local medullary growth represents an opportunity for future studies with alternative coating methods to fine-tune the local release of ZA from the coating and enhance complete osseointegration of the implant.

Bone metastases in midgut neuroendocrine tumors: imaging characteristics, distribution, and risk factors.

PURPOSE: Bone metastases (BM) affect 10-30% of patients with small intestine neuroendocrine tumors (siNET), but little descriptive data are available regarding their distribution throughout the skeleton or potential risk factors. Aim of the study is to better describe the imaging characteristics, distribution, and risk factors of siNET bone metastases using 18F-FDOPA PET/CT. METHODS: All patients with well-differentiated siNET who underwent an 18F-DOPA PET/CT examination in our institution were retrospectively screened between October 2017 and February 2020. Location, SUVmax and CT density of each BM were collected. Sex, metabolic tumor volume (MTV) excluding bone, and metastatic sites other than bone were studied to determine risk factors of BM. RESULTS: Among the 69 patients included, 11 patients (15.9%) presented BM on 18F-FDOPA (65 metastases). The most frequently involved sites were: thoracic spine, pelvic bones and ribs. About 64% of patients presented multiple BM. On coupled CT scan, 63% of BM were not visible. Using an optimal threshold of 19.2 ml, MTV was an independent predictor of BM (p = 0.004) with a derived sensitivity of 100% [65.0-100.0] and a specificity of 70.9% [57.7-81.2]. Hepatic metastatic involvement was also a significant predictor of BM (p = 0.044). CONCLUSION: The development of BM in siNETs appears to be a late event, occurring in patients with a high tumor burden and hepatic involvement. They are often multiple and predominate in the axial skeleton.

Hydrogen-bonds mediate liquid-liquid phase separation of mussel derived adhesive peptides.

Marine mussels achieve strong underwater adhesion by depositing mussel foot proteins (Mfps) that form coacervates during the protein secretion. However, the molecular mechanisms that govern the phase separation behaviors of the Mfps are still not fully understood. Here, we report that GK-16*, a peptide derived from the primary adhesive protein Mfp-5, forms coacervate in seawater conditions. Molecular dynamics simulations combined with point mutation experiments demonstrate that Dopa- and Gly- mediated hydrogen-bonding interactions are essential in the coacervation process. The properties of GK-16* coacervates could be controlled by tuning the strength of the electrostatic and Dopa-mediated hydrogen bond interactions via controlling the pH and salt concentration of the solution. The GK-16* coacervate undergoes a pH induced liquid-to-gel transition, which can be utilized for the underwater delivery and curing of the adhesives. Our study provides useful molecular design principles for the development of mussel-inspired peptidyl coacervate adhesives with tunable properties.

Activation studies with amino acids and amines of a ß-carbonic anhydrase from Mammaliicoccus (Staphylococcus) sciuri previously annotated as Staphylococcus aureus (SauBCA) carbonic anhydrase.

A ß-carbonic anhydrase (CA, EC 4.2.1.1) previously annotated to be present in the genome of Staphylococcus aureus, SauBCA, has been shown to belong to another pathogenic bacterium, Mammaliicoccus (Staphylococcus) sciuri. This enzyme, MscCA, has been investigated for its activation with a series of natural and synthetic amino acid and amines, comparing the results with those obtained for the ortholog enzyme from Escherichia coli, EcoCAß. The best MscCA activators were D-His, L- and D-DOPA, 4-(2-aminoethyl)-morpholine and L-Asn, which showed KAs of 0.12 - 0.89 µM. The least efficient activators were D-Tyr and L-Gln (KAs of 13.9 - 28.6 µM). The enzyme was also also inhibited by anions and sulphonamides, as described earlier. Endogenous CA activators may play a role in bacterial virulence and colonisation of the host which makes this research topic of great interest.

Engineering Bio-Adhesives Based on Protein-Polysaccharide Phase Separation.

Glue-type bio-adhesives are in high demand for many applications, including hemostasis, wound closure, and integration of bioelectronic devices, due to their injectable ability and in situ adhesion. However, most glue-type bio-adhesives cannot be used for short-term tissue adhesion due to their weak instant cohesion. Here, we show a novel glue-type bio-adhesive based on the phase separation of proteins and polysaccharides by functionalizing polysaccharides with dopa. The bio-adhesive exhibits increased adhesion performance and enhanced phase separation behaviors. Because of the cohesion from phase separation and adhesion from dopa, the bio-adhesive shows excellent instant and long-term adhesion performance for both organic and inorganic substrates. The long-term adhesion strength of the bio-glue on wet tissues reached 1.48 MPa (shear strength), while the interfacial toughness reached ~880 J m-2. Due to the unique phase separation behaviors, the bio-glue can even work normally in aqueous environments. At last, the feasibility of this glue-type bio-adhesive in the adhesion of various visceral tissues in vitro was demonstrated to have excellent biocompatibility. Given the convenience of application, biocompatibility, and robust bio-adhesion, we anticipate the bio-glue may find broad biomedical and clinical applications.

Design, synthesis, and characterization of a novel dual cross-linked gelatin-based bioadhesive for hard and soft tissues adhesion capability.

Many surgical treatments require a suitable tissue adhesive that maintains its performance in wet conditions and can be applied simultaneously for hard and soft tissues. In the present study, a dual cross-linked tissue adhesive was synthesized by mixing the gelatin methacryloyl (Gel-MA) and gelatin-dopamine conjugate (Gel-Dopa). The setting reaction was based on a photopolymerization process in the presence of a combination of riboflavin and triethanolamine and a chemical cross-linking process attributed to the genipin as a natural cross-linker. Modified gelatin macromolecules were characterized and the best wavelength for free radical generation in the presence of riboflavin was obtained. Tissue adhesives were prepared with 30% hydrogels of Gel-MA and Gel-Dopa with different ratios in distilled water. The gelation occurred in a short time after light irradiation. The chemical, mechanical, physical, and cytotoxicity properties of the tissue adhesives were evaluated. The results showed that despite photopolymerization, chemical crosslinking with genipin played a more critical role in the setting process. Water uptake, degradation behavior, cytotoxicity, and adhesion properties of the adhesives were correlated with the ratio of the components. The SEM images showed a porous structure that could ensure the entry of cells and nutrients into the surgical area. While acceptable properties in most experiments were observed, all features were improved as the Gel-Dopa ratio increased. Also, the obtained hydrogels revealed excellent adhesive properties, particularly with bone even after wet incubation, and it was attributed to the amount of gelatin-dopamine conjugate. From the obtained results, it was concluded that a dual adhesive hydrogel based on gelatin macromolecules could be a good candidate as a tissue adhesive in wet condition.

Bipolar electrochemical rotors for the direct transduction of molecular chiral information.

Efficient monitoring of chiral information of bioactive compounds has gained considerable attention, due to their involvement in different biochemical processes. In this work, we propose a novel dynamic system for the easy and straightforward recognition of chiral redox active molecules and its possible use for the efficient measurement of enantiomeric excess in solution. The approach is based on the synergy between the localized enantioselective oxidation of only one of the two antipodes of a chiral molecule and the produced charge-compensating asymmetric proton flux along a bipolar electrode. The resulting clockwise or anticlockwise rotation is triggered only when the probe with the right chirality is present in solution. The angle of rotation shows a linear correlation with the analyte concentration, enabling the quantification of enantiomeric ratios in mixtures where the two antipodes are present in solution. This device was successfully used to simultaneously measure different ratios of the enantiomers of 3,4-dihydroxyphenylalanine and tryptophan. The versatility of the proposed approach opens up the possibility to use such a dynamic system as a straightforward (bio)analytical tool for the qualitative and quantitative discrimination of different redox active chiral probes.