[68 Ga]Ga-FAPI-46 PET for non-invasive detection of pulmonary fibrosis disease activity.

PURPOSE: The lack of effective molecular biomarkers to monitor idiopathic pulmonary fibrosis (IPF) activity or treatment response remains an unmet clinical need. Herein, we determined the utility of fibroblast activation protein inhibitor for positron emission tomography (FAPI PET) imaging in a mouse model of pulmonary fibrosis. METHODS: Pulmonary fibrosis was induced by intratracheal administration of bleomycin (1 U/kg) while intratracheal saline was administered to control mice. Subgroups from each cohort (n = 3-5) underwent dynamic 1 h PET/CT after intravenously injecting FAPI-46 radiolabeled with gallium-68 ([68 Ga]Ga-FAPI-46) at 7 days and 14 days following disease induction. Animals were sacrificed following imaging for ex vivo gamma counting and histologic correlation. [68 Ga]Ga-FAPI-46 uptake was quantified and reported as percent injected activity per cc (%IA/cc) or percent injected activity (%IA). Lung CT density in Hounsfield units (HU) was also correlated with histologic examinations of lung fibrosis. RESULTS: CT only detected differences in the fibrotic response at 14 days post-bleomycin administration. [68 Ga]Ga-FAPI-46 lung uptake was significantly higher in the bleomycin group than in control subjects at 7 days and 14 days. Significantly (P = 0.0012) increased [68 Ga]Ga-FAPI-46 lung uptake in the bleomycin groups at 14 days (1.01 ± 0.12%IA/cc) vs. 7 days (0.33 ± 0.09%IA/cc) at 60 min post-injection of the tracer was observed. These findings were consistent with an increase in both fibrinogenesis and FAP expression as seen in histology. CONCLUSION: CT was unable to assess disease activity in a murine model of IPF. Conversely, FAPI PET detected both the presence and activity of lung fibrogenesis, making it a promising tool for assessing early disease activity and evaluating the efficacy of therapeutic interventions in lung fibrosis patients.

Ultrasmall Porous Silica Nanoparticles with Enhanced Pharmacokinetics for Cancer Theranostics.

Theranostic nanoparticles hold the potential to greatly improve cancer management by providing personalized medicine. Although many theranostic nanoconstructs have been successful in preclinical studies, clinical translation is still hampered by their limited targeting capability and lack of successful therapeutic efficacy. We report the use of novel ultrasmall porous silica nanoparticles (UPSN) with enhanced in vivo pharmacokinetics such as high target tissue accumulation (12% ID/g in the tumor) and evasion from the reticuloendothelial system (RES) organs. Herein, UPSN is conjugated with the isotopic pair 90/86Y, enabling both noninvasive imaging as well as internal radiotherapy. In vivo PET imaging demonstrates prolonged blood circulation and excellent tumor contrast with 86Y-DOTA-UPSN. Tumor-to-muscle and tumor-to-liver uptake values were significantly high (12.4 ± 1.7 and 1.5 ± 0.5, respectively), unprecedented for inorganic nanomaterials. 90Y-DOTA-UPSN significantly inhibits tumor growth and increases overall survival, indicating the promise of UPSN for future clinical translation as a cancer theranostic agent.

ImmunoPET of CD146 in Orthotopic and Metastatic Breast Cancer Models.

The overexpression of CD146 in breast cancer is considered a hallmark of tumor progression and metastasis, particularly in triple negative breast cancer. Aimed at imaging differential CD146 expressions in breast cancer, a noninvasive method for predictive prognosis and diagnosis was investigated using a 64Cu-labeled CD146-specific monoclonal antibody, YY146. CD146 expression was screened in human breast cancer cell lines using Western blotting. Binding ability was evaluated using flow cytometry and immunofluorescent staining. YY146 was conjugated with 1,4,7-triazacyclononane-triacetic acid (NOTA) and radiolabeled with 64Cu following standard procedures. Serial PET or PET/CT imaging was performed in orthotopic and metastatic breast cancer tumor models. Biodistribution was performed after the final time point of imaging. Finally, tissue immunofluorescent staining and hematoxylin and eosin (H&E) staining were performed on tumor tissues. The MDA-MB-435 cell line showed the highest CD146 expression level, whereas MCF-7 had the lowest level at the cellular level. ImmunoPET showed that MDA-MB-435 orthotopic tumors had high and clear radioactive accumulation after the administration of 64Cu-NOTA-YY146. The tumor uptake of 64Cu-NOTA-YY146 in MDA-MB-435 was significantly higher than that in MCF-7 and nonspecific IgG control groups (P < 0.01). Biodistribution verified the PET imaging results. For metastatic models, 64Cu-NOTA-YY146 allowed for the visualization of high radioactivity accumulation in metastatic MDA-MB-435 tumors, which was confirmed by ex vivo biodistribution of lung tissues. H&E staining proved the successful building of metastatic tumor models. Immunofluorescent staining verified the differential expression of CD146 in orthotopic tumors. Therefore, 64Cu-NOTA-YY146 could be used as an immunoPET probe to visualize CD146 in the breast cancer model and is potentially useful for cancer diagnosis, prognosis prediction, and monitoring therapeutic response.

86/90Y-Labeled Monoclonal Antibody Targeting Tissue Factor for Pancreatic Cancer Theranostics.

Pancreatic cancer is highly aggressive, with a median survival time of less than 6 months and a 5-year overall survival rate of around 7%. The poor prognosis of PaCa is largely due to its advanced stage at diagnosis and the lack of efficient therapeutic options. Thus, the development of an efficient, multifunctional PaCa theranostic system is urgently needed. Overexpression of tissue factor (TF) has been associated with increased tumor growth, angiogenesis, and metastasis in many malignancies, including pancreatic cancer. Herein, we propose the use of a TF-targeted monoclonal antibody (ALT836) conjugated with the pair 86/90Y as a theranostic agent against pancreatic cancer. For methods, serial PET imaging with 86Y-DTPA-ALT836 was conducted to map the biodistribution the tracer in BXPC-3 tumor-bearing mice. 90Y-DTPA-ALT836 was employed as a therapeutic agent that also allowed tumor burden monitoring through Cherenkov luminescence imaging. The results were that the uptake of 86Y-DTPA-ALT836 in BXPC-3 xenograft tumors was high and increased over time up to 48 h postinjection (p.i.), corroborated through ex vivo biodistribution studies and further confirmed by Cherenkov luminescence Imaging. In therapeutic studies, 90Y-DTPA-ALT836 was found to slow tumor growth relative to the control groups and had significantly smaller (p < 0.05) tumor volumes 1 day p.i. Histological analysis of ex vivo tissues revealed significant damage to the treated tumors. The conclusion is that the use of the 86/90Y theranostic pair allows PET imaging with excellent tumor-to-background contrast and treatment of TF-expressing pancreatic tumors with promising therapeutic outcomes.

Size-Optimized Ultrasmall Porous Silica Nanoparticles Depict Vasculature-Based Differential Targeting in Triple Negative Breast Cancer.

Rapid sequestration and prolonged retention of intravenously injected nanoparticles by the liver and spleen (reticuloendothelial system (RES)) presents a major barrier to effective delivery to the target site and hampers clinical translation of nanomedicine. Inspired by biological macromolecular drugs, synthesis of ultrasmall (diameter ≈12-15 nm) porous silica nanoparticles (UPSNs), capable of prolonged plasma half-life, attenuated RES sequestration, and accelerated hepatobiliary clearance, is reported. The study further investigates the effect of tumor vascularization on uptake and retention of UPSNs in two mouse models of triple negative breast cancer with distinctly different microenvironments. A semimechanistic mathematical model is developed to gain mechanistic insights into the interactions between the UPSNs and the biological entities of interest, specifically the RES. Despite similar systemic pharmacokinetic profiles, UPSNs demonstrate strikingly different tumor responses in the two models. Histopathology confirms the differences in vasculature and stromal status of the two models, and corresponding differences in the microscopic distribution of UPSNs within the tumors. The studies demonstrate the successful application of multidisciplinary and complementary approaches, based on laboratory experimentation and mathematical modeling, to concurrently design optimized nanomaterials, and investigate their complex biological interactions, in order to drive innovation and translation.

Radionuclide-Activated Nanomaterials and Their Biomedical Applications.

Radio-nanomedicine, or the use of radiolabeled nanoparticles in nuclear medicine, has attracted much attention in the last few decades. Since the discovery of Cerenkov radiation and its employment in Cerenkov luminescence imaging, the combination of nanomaterials and Cerenkov radiation emitters has been revolutionizing the way nanomaterials are perceived in the field: from simple inert carriers of radioactivity to activatable nanomaterials for both diagnostic and therapeutic applications. Herein, we provide a comprehensive review on the types of nanomaterials that have been used to interact with Cerenkov radiation and the gamma and beta scintillation of radionuclides, as well as on their biological applications.

Magnetic Targeting of Nanotheranostics Enhances Cerenkov Radiation-Induced Photodynamic Therapy.

The interaction between radionuclides and nanomaterials could generate Cerenkov radiation (CR) for CR-induced photodynamic therapy (PDT) without requirement of external light excitation. However, the relatively weak CR interaction leaves clinicians uncertain about the benefits of this new type of PDT. Therefore, a novel strategy to amplify the therapeutic effect of CR-induced PDT is imminently required to overcome the disadvantages of traditional nanoparticulate PDT such as tissue penetration limitation, external light dependence, and low tumor accumulation of photosensitizers. Herein, magnetic nanoparticles (MNPs) with 89Zr radiolabeling and porphyrin molecules (TCPP) surface modification (i.e., 89Zr-MNP/TCPP) were synthesized for CR-induced PDT with magnetic targeting tumor delivery. As a novel strategy to break the depth and light dependence of traditional PDT, these 89Zr-MNP/TCPP exhibited high tumor accumulation under the presence of an external magnetic field, contributing to excellent tumor photodynamic therapeutic effect together with fluorescence, Cerenkov luminescence (CL), and Cerenkov resonance energy transfer (CRET) multimodal imaging to monitor the therapeutic process. The present study provides a major step forward in photodynamic therapy by developing an advanced phototherapy tool of magnetism-enhanced CR-induced PDT for effective targeting and treatment of tumors.

Targeting angiogenesis for radioimmunotherapy with a 177Lu-labeled antibody.

PURPOSE: Increased angiogenesis is a marker of aggressiveness in many cancers. Targeted radionuclide therapy of these cancers with angiogenesis-targeting agents may curtail this increased blood vessel formation and slow the growth of tumors, both primary and metastatic. CD105, or endoglin, has a primary role in angiogenesis in a number of cancers, making this a widely applicable target for targeted radioimmunotherapy. METHODS: The anti-CD105 antibody, TRC105 (TRACON Pharmaceuticals), was conjugated with DTPA for radiolabeling with 177Lu (t 1/2 6.65 days). Balb/c mice were implanted with 4T1 mammary carcinoma cells, and five study groups were used: 177Lu only, TRC105 only, 177Lu-DTPA-IgG (a nonspecific antibody), 177Lu-DTPA-TRC105 low-dose, and 177Lu-DTPA-TRC105 high-dose. Toxicity of the agent was monitored by body weight measurements and analysis of blood markers. Biodistribution studies of 177Lu-DTPA-TRC105 were also performed at 1 and 7 days after injection. Ex vivo histology studies of various tissues were conducted at 1, 7, and 30 days after injection of high-dose 177Lu-DTPA-TRC105. RESULTS: Biodistribution studies indicated steady uptake of 177Lu-DTPA-TRC105 in 4T1 tumors between 1 and 7 days after injection (14.3 ± 2.3%ID/g and 11.6 ± 6.1%ID/g, respectively; n = 3) and gradual clearance from other organs. Significant inhibition of tumor growth was observed in the high-dose group, with a corresponding significant increase in survival (p < 0.001, all groups). In most study groups (all except the nonspecific IgG group), the body weights of the mice did not decrease by more than 10%, indicating the safety of the injected agents. Serum alanine transaminase levels remained nearly constant indicating no damage to the liver (a primary clearance organ of the agent), and this was confirmed by ex vivo histological analyses. CONCLUSION: 177Lu-DTPA-TRC105, when administered at a sufficient dose, is able to curtail tumor growth and provide a significant survival benefit without off-target toxicity. Thus, this targeted agent could be used in combination with other treatment options to slow tumor growth allowing the other agents to be more effective.

ImmunoPET of CD146 in a Murine Hindlimb Ischemia Model.

Peripheral arterial disease (PAD) consists of a persistent obstruction of lower-extremity arteries further from the aortic bifurcation attributable to atherosclerosis. PAD is correlated with an elevated risk of morbidity and mortality as well as of deterioration of the quality of life with claudication and chronic leg ischemia being the most frequent complications. Therapeutic angiogenesis is a promising therapeutic strategy that aims to restore the blood flow to the ischemic limb. In this context, assessing the efficacy of pro-angiogenic treatment using a reliable noninvasive imaging technique would greatly benefit the implementation of this therapeutic approach. Herein, we describe the angiogenesis and perfusion recovery characteristics of a mouse model of PAD via in vivo positron emission tomography (PET) imaging of CD146 expression. For that, ischemia was generated by ligation and excision of the right femoral artery of Balb/C mice and confirmed through laser Doppler imaging. The angiogenic process, induced by ischemia, was noninvasively monitored and quantified through PET imaging of CD146 expression in the injured leg using a 64Cu-labeled anti-CD146 monoclonal antibody, 64Cu-NOTA-YY146, at post-operative days 3, 10, and 17. The CD146-specific character of 64Cu-NOTA-YY146 was verified via a blocking study performed in another cohort at day 10 after surgery. Tracer uptake was correlated with in situ CD146 expression by histological analysis. PET scan results indicated that 64Cu-NOTA-YY146 uptake in the injured leg was significantly higher, with the highest uptake with a value of 14.1 ± 2.0 %ID/g at post-operative day 3, compared to the normal contralateral hindlimb, at all time points (maximum uptake of 2.2 ± 0.2 %ID/g). The pre-injection of a blocking dose resulted in a significantly lower tracer uptake in the ischemic hindlimb on day 10 after surgery, confirming tracer specificity. CD146/CD31 immunofluorescent co-staining showed an excellent correlation between the high uptake of the tracer with in situ CD146 expression levels and a marked co-localization of CD146 and CD31 signals. In conclusion, persistent and CD146-specific tracer accumulation in the ischemic hindlimb was observed, confirming the feasibility of 64Cu-NOTA-YY146 to be used as an imaging agent to monitor the progression of angiogenesis and recovery in future PAD research.

86/90Y-Based Theranostics Targeting Angiogenesis in a Murine Breast Cancer Model.

Angiogenesis is widely recognized as one of the hallmarks of cancer. Therefore, imaging and therapeutic agents targeted to angiogenic vessels may be widely applicable in many types of cancer. To this end, the theranostic isotope pair, 86Y and 90Y, were used to create a pair of agents for targeted imaging and therapy of neovasculature in murine breast cancer models using a chimeric anti-CD105 antibody, TRC105. Serial positron emission tomography imaging with 86Y-DTPA-TRC105 demonstrated high uptake in 4T1 tumors, peaking at 9.6 ± 0.3%ID/g, verified through ex vivo studies. Additionally, promising results were obtained in therapeutic studies with 90Y-DTPA-TRC105, wherein significantly ( p < 0.05) decreased tumor volumes were observed for the targeted treatment group over all control groups near the end of the study. Dosimetric extrapolation and tissue histological analysis corroborated trends found in vivo. Overall, this study demonstrated the potential of the pair 86/90Y for theranostics, enabling personalized treatments for cancer.

Efficient Uptake of 177 Lu-Porphyrin-PEG Nanocomplexes by Tumor Mitochondria for Multimodal-Imaging-Guided Combination Therapy.

The benefits to intracellular drug delivery from nanomedicine have been limited by biological barriers and to some extent by targeting capability. We investigated a size-controlled, dual tumor-mitochondria-targeted theranostic nanoplatform (Porphyrin-PEG Nanocomplexes, PPNs). The maximum tumor accumulation (15.6 %ID g-1 , 72 h p.i.) and ideal tumor-to-muscle ratio (16.6, 72 h p.i.) was achieved using an optimized PPN particle size of approximately 10 nm, as measured by using PET imaging tracing. The stable coordination of PPNs with 177 Lu enables the integration of fluorescence imaging (FL) and photodynamic therapy (PDT) with positron emission tomography (PET) imaging and internal radiotherapy (RT). Furthermore, the efficient tumor and mitochondrial uptake of 177 Lu-PPNs greatly enhanced the efficacies of RT and/or PDT. This work developed a facile approach for the fabrication of tumor-targeted multi-modal nanotheranostic agents, which enables precision and radionuclide-based combination tumor therapy.

Evaluation of linear versus star-like polymer anti-cancer nanomedicines in mouse models.

Nanomedicines are considered next generation therapeutics with advanced therapeutic properties and reduced side effects. Herein, we introduce tailored linear and star-like water-soluble nanosystems as stimuli-sensitive nanomedicines for the treatment of solid tumors or hematological malignancies. The polymer carrier and drug pharmacokinetics were independently evaluated to elucidate the relationship between the nanosystem structure and its distribution in the body. Positron emission tomography and optical imaging demonstrated enhanced tumor accumulation of the polymer carriers in 4T1-bearing mice with increased tumor-to-blood and tumor-to-muscle ratios. Additionally, there was a significant accumulation of doxorubicin bound to various polymer carriers in EL4 tumors, as well as excellent in vivo therapeutic activity in EL4 lymphoma and moderate efficacy in 4T1 breast carcinoma. The linear nanomedicine showed at least comparable pharmacologic properties to the star-like nanomedicines regarding doxorubicin transport. Therefore, if multiple parameters are considered such as its optimized structure and simple and reproducible synthesis, this polymer carrier system is the most promising for further preclinical and clinical investigations.

Advanced Face Mask Filters Based on PCL Electrospun Meshes Dopped with Antimicrobial MgO and CuO Nanoparticles.

The pandemic situation caused by coronavirus clearly demonstrated the need for alternatives able to protect the respiratory tract and inactivate the infectious agents. Based on this, antibacterial face-mask filters of polycaprolactone (PCL) dopped with magnesium oxide (MgO) and copper oxide (CuO) nanoparticles (NPs) were produced using an electrospinning technique. A morphological analysis of electrospun meshes evaluated the success of nanoparticles' incorporation as well as the average fibers' diameters (481 ± 272 nm). The performance of electrospun nanofibers was also assessed in terms of tensile strength (0.88 ± 0.25 MPa), water vapor permeability (11,178.66 ± 35.78 g·m-2·day-1), stability under wet conditions and antibacterial activity according to the standard guidelines. The filters showed structural stability up to 2 h of washing and improved antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) for optimized concentrations of MgO and CuO NPs. Overall, electrospun meshes with antibacterial activity were successfully developed for advanced filtering applications.

Electrospun-Based Membranes as a Key Tool to Prevent Respiratory Infections.

The use of electrospun meshes has been proposed as highly efficient protective equipment to prevent respiratory infections. Those infections can result from the activity of micro-organisms and other small dust particles, such as those resulting from air pollution, that impair the respiratory tract, induce cellular damage and compromise breathing capacity. Therefore, electrospun meshes can contribute to promoting air-breathing quality and controlling the spread of such epidemic-disrupting agents due to their intrinsic characteristics, namely, low pore size, and high porosity and surface area. In this review, the mechanisms behind the pathogenesis of several stressors of the respiratory system are covered as well as the strategies adopted to inhibit their action. The main goal is to discuss the performance of antimicrobial electrospun nanofibers by comparing the results already reported in the literature. Further, the main aspects of the certification of filtering systems are highlighted, and the expected technology developments in the industry are also discussed.

Antitumor efficacy of 90Y-NM600 targeted radionuclide therapy and PD-1 blockade is limited by regulatory T cells in murine prostate tumors.

BACKGROUND: Systemic radiation treatments that preferentially irradiate cancer cells over normal tissue, known as targeted radionuclide therapy (TRT), have shown significant potential for treating metastatic prostate cancer. Preclinical studies have demonstrated the ability of external beam radiation therapy (EBRT) to sensitize tumors to T cell checkpoint blockade. Combining TRT approaches with immunotherapy may be more feasible than combining with EBRT to treat widely metastatic disease, however the effects of TRT on the prostate tumor microenvironment alone and in combinfation with checkpoint blockade have not yet been studied. METHODS: C57BL/6 mice-bearing TRAMP-C1 tumors and FVB/NJ mice-bearing Myc-CaP tumors were treated with a single intravenous administration of either low-dose or high-dose 90Y-NM600 TRT, and with or without anti-PD-1 therapy. Groups of mice were followed for tumor growth while others were used for tissue collection and immunophenotyping of the tumors via flow cytometry. RESULTS: 90Y-NM600 TRT was safe at doses that elicited a moderate antitumor response. TRT had multiple effects on the tumor microenvironment including increasing CD8 +T cell infiltration, increasing checkpoint molecule expression on CD8 +T cells, and increasing PD-L1 expression on myeloid cells. However, PD-1 blockade with TRT treatment did not improve antitumor efficacy. Tregs remained functional up to 1 week following TRT, but CD8 +T cells were not, and the suppressive function of Tregs increased when anti-PD-1 was present in in vitro studies. The combination of anti-PD-1 and TRT was only effective in vivo when Tregs were depleted. CONCLUSIONS: Our data suggest that the combination of 90Y-NM600 TRT and PD-1 blockade therapy is ineffective in these prostate cancer models due to the activating effect of anti-PD-1 on Tregs. This finding underscores the importance of thorough understanding of the effects of TRT and immunotherapy combinations on the tumor immune microenvironment prior to clinical investigation.

Internally Responsive Nanomaterials for Activatable Multimodal Imaging of Cancer.

Advances in technology and nanomedicine have led to the development of nanoparticles that can be activated for multimodal imaging of cancer, where a stimulus induces a material modification that enhances image contrast. Multimodal imaging using nanomaterials with this capability can combine the advantages and overcome the limitations of any single imaging modality. When designed with stimuli-responsive abilities, the target-to-background ratio of multimodal imaging nanoprobes increases because specific stimuli in the tumor enhance the signal. Several aspects of the tumor microenvironment can be exploited as an internal stimulus response for multimodal imaging applications, such as the pH gradient, redox processes, overproduction of various enzymes, or combinations of these. In this review, design strategies are discussed and an overview of the recent developments of internally responsive multimodal nanomaterials is provided. Properly implementing this approach improves noninvasive cancer diagnosis and staging as well as provides a method to monitor drug delivery and treatment response.

Non-invasive Detection of Immunotherapy-Induced Adverse Events.

PURPOSE: Cancer immunotherapy has markedly improved the prognosis of patients with a broad variety of malignancies. However, benefits are weighed against unique toxicities, with immune-related adverse events (irAE) that are frequent and potentially life-threatening. The diagnosis and management of these events are challenging due to heterogeneity of timing onset, multiplicity of affected organs, and lack of non-invasive monitoring techniques. We demonstrate the use of a granzyme B-targeted PET imaging agent (GZP) for irAE identification in a murine model. EXPERIMENTAL DESIGN: We generated a model of immunotherapy-induced adverse events in Foxp3-DTR-GFP mice bearing MC38 tumors. GZP PET imaging was performed to evaluate organs non-invasively. We validated imaging with ex vivo analysis, correlating the establishment of these events with the presence of immune infiltrates and granzyme B upregulation in tissue. To demonstrate the clinical relevance of our findings, the presence of granzyme B was identified through immunofluorescence staining in tissue samples of patients with confirmed checkpoint inhibitor-associated adverse events. RESULTS: GZP PET imaging revealed differential uptake in organs affected by irAEs, such as colon, spleen, and kidney, which significantly diminished after administration of the immunosuppressor dexamethasone. The presence of granzyme B and immune infiltrates were confirmed histologically and correlated with significantly higher uptake in PET imaging. The presence of granzyme B was also confirmed in samples from patients that presented with clinical irAEs. CONCLUSIONS: We demonstrate an interconnection between the establishment of irAEs and granzyme B presence and, for the first time, the visualization of those events through PET imaging.

Multifunctional Gelatin/Chitosan Electrospun Wound Dressing Dopped with Undaria pinnatifida Phlorotannin-Enriched Extract for Skin Regeneration.

The similarities of electrospun fibers with the skin extracellular matrix (ECM) make them promising structures for advanced wound dressings. Moreover, infection and resistance in wounds are a major health concern that may be reduced with antibacterial wound dressings. In this work, a multifunctional wound dressing was developed based on gelatin/chitosan hybrid fibers dopped with phlorotannin-enrich extract from the seaweed Undaria pinnatifida. The intrinsic electrospun structure properties combined with the antimicrobial and anti-inflammatory properties of phlorotannin-enrich extract will enhance the wound healing process. Electrospun meshes were produced by incorporating 1 or 2 wt% of extract, and the structure without extract was used as a control. Physico-chemical, mechanical, and biological properties were evaluated for all conditions. Results demonstrated that all developed samples presented a homogenous fiber deposition with the average diameters closer to the native ECM fibrils, and high porosities (~90%) that will be crucial to control the wound moist environment. According to the tensile test assays, the incorporation of phlorotannin-enriched extract enhances the elastic performance of the samples. Additionally, the extract incorporation made the structure stable over time since its in vitro degradation rates decreased under enzymatic medium. Extract release profile demonstrated a longstanding delivery (up to 160 days), reaching a maximum value of ~98% over time. Moreover, the preliminary antimicrobial results confirm the mesh's antimicrobial activity against Pseudomonas aeruginosa and Staphylococcus aureus. In terms of biological characterization, no condition presented cytotoxicity effects on hDNF cells, allowing their adhesion and proliferation over 14 days, except the condition of 2 wt% after 7 days. Overall, the electrospun structure comprising phlorotannins-enriched extract is a promising bioactive structure with potential to be used as a drug delivery system for skin regeneration by reducing the bacterial infection in the wound bed.

A Biorefinery Approach to the Biomass of the Seaweed Undaria pinnatifida (Harvey Suringar, 1873): Obtaining Phlorotannins-Enriched Extracts for Wound Healing.

Brown seaweeds are recognized sources of compounds with a wide range of properties and applications. Within these compounds, phlorotannins are known to possess several bioactivities (e.g., antioxidant, anti-inflammatory, and antimicrobial) with potential to improve wound healing. To obtain phlorotannins enriched extracts from Undaria pinnatifida, a biorefinery was set using low-cost industry-friendly methodologies, such as sequential solid-liquid extraction and liquid-liquid extraction. The obtained extracts were screened for their antioxidant and antimicrobial activity against five common wound pathogens and for their anti-inflammatory potential. The ethanolic wash fraction (wE100) had the highest antioxidant activity (114.61 ± 10.04 mmol·mg-1 extract by Diphenyl-1-picrylhydrazyl (DPPH) and 6.56 ± 1.13 mM eq. Fe II·mg-1 extract by and Ferric Reducing Antioxidant Power (FRAP)), acting efficiently against Gram-negative (Pseudomonas aeruginosa) and Gram-positive (Staphylococcus aureus) bacteria, and showing a nitric oxide production inhibition over 47% when used at 0.01 µg·mL-1. NMR and FTIR chemical characterization suggested that phlorotannins are present. Obtained fraction wE100 proved to be a promising candidate for further inclusion as wound healing agents, while the remaining fractions analyzed are potential sources for other biotechnological applications, giving emphasis to a biorefinery and circular economy framework to add value to this seaweed and the industry.