Double-interpenetrating nanostructured networks of marine polysaccharides possessing properties comparable to synthetic polymers.

Sustainable circular economy requires materials that possess a property profile comparable to synthetic polymers and, additionally, processing and sourcing of raw materials that have a small environmental footprint. Here, we present a paradigm for processing marine biopolymers into materials that possess both elastic and plastic behavior within a single system involving a double-interpenetrating polymer network comprising the elastic phase of dynamic physical cross-links and stress-dissipating ionically cross-linked domains. As a proof of principle, films possessing more than twofold higher elastic modulus, ultimate tensile strength, and yield stress than those of polylactic acid were realized by blending two water-soluble marine polysaccharides, namely alginic acid (Alg) with physically cross-linkable carboxylated agarose (CA) followed by ionic cross-linking with a divalent cation. Dried CAAlg films showed homogeneous nano-micro-scale domains, with yield stress and size of the domains scaling inversely with calcium concentration. Through surface activation/cross-linking using calcium, CAAlg films could be further processed using wet bonding to yield laminated structures with interfacial failure loads (13.2 ± 0.81 N) similar to the ultimate loads of unlaminated films (10.09 ± 1.47 N). Toward the engineering of wood-marine biopolymer composites, an array of lines of CAAlg were printed on wood veneers (panels), dried, and then bonded following activation with calcium to yield fully bonded wood two-ply laminate. The system presented herein provides a blueprint for the adoption of marine algae-derived polysaccharides in the development of sustainable high-performance materials.

Reversible, ß-sheet-dependent self-assembly of the phosphoprotein phosvitin is controlled by the concentration and valency of cations.

The hyperphosphorylated protein phosvitin (PV) undergoes a pH-dependent transition between PII- and ß-sheet secondary structures, a process deemed crucial for its role in the promotion of biogenic apatite formation. The transition occurs surprisingly slowly (minutes to hours). This is consistent with a slow aggregation process involving ionic interactions of charged groups on the protein surface. Herein, we determined the associated transition pK values and time constants through matrix least-squares (MLS) global fitting of a series of pH- and time-dependent circular dichroism (CD) spectra recorded in the presence of different mono-, bi- and trivalent cations. Supporting our results with dynamic light scattering data, we clearly identified a close correlation of ß-sheet transition and the formation of small aggregates at low pH. This process is inhibited in the presence of all tested cations with the strongest effects for trivalent cations (Fe3+ and Al3+). In the presence of Ca2+ and Mg2+, larger higher-order particles are formed from PV in the ß-sheet conformation, as identified from the interpretation of differential scattering observed in the CD spectra. Our observations are consistent with the existence of a multi-step equilibrium between aggregated and non-aggregated species of PV. The equilibrium is highly sensitive to the environment pH and salt concentration with exceptional behavior in the presence of divalent cations such as Ca2+ and Mg2+.

3D Printed Solutions for Spheroid Engineering and Cancer Research.

In multicellular organisms, cells are organized in a 3-dimensional framework and this is essential for organogenesis and tissue morphogenesis. Systems to recapitulate 3D cell growth are therefore vital for understanding development and cancer biology. Cells organized in 3D environments can evolve certain phenotypic traits valuable to physiologically relevant models that cannot be accessed in 2D culture. Cellular spheroids constitute an important aspect of in vitro tumor biology and they are usually prepared using the hanging drop method. Here a 3D printed approach is demonstrated to fabricate bespoke hanging drop devices for the culture of tumor cells. The design attributes of the hanging drop device take into account the need for high-throughput, high efficacy in spheroid formation, and automation. Specifically, in this study, custom-fit, modularized hanging drop devices comprising of inserts (Q-serts) were designed and fabricated using fused filament deposition (FFD). The utility of the Q-serts in the engineering of unicellular and multicellular spheroids-synthetic tumor microenvironment mimics (STEMs)-was established using human (cancer) cells. The culture of spheroids was automated using a pipetting robot and bioprinted using a custom bioink based on carboxylated agarose to simulate a tumor microenvironment (TME). The spheroids were characterized using light microscopy and histology. They showed good morphological and structural integrity and had high viability throughout the entire workflow. The systems and workflow presented here represent a user-focused 3D printing-driven spheroid culture platform which can be reliably reproduced in any research environment and scaled to- and on-demand. The standardization of spheroid preparation, handling, and culture should eliminate user-dependent variables, and have a positive impact on translational research to enable direct comparison of scientific findings.

Hydrogel-Forming Algae Polysaccharides: From Seaweed to Biomedical Applications.

With the increasing growth of the algae industry and the development of algae biorefinery, there is a growing need for high-value applications of algae-extracted biopolymers. The utilization of such biopolymers in the biomedical field can be considered as one of the most attractive applications but is challenging to implement. Historically, polysaccharides extracted from seaweed have been used for a long time in biomedical research, for example, agarose gels for electrophoresis and bacterial culture. To overcome the current challenges in polysaccharides and help further the development of high-added-value applications, an overview of the entire polysaccharide journey from seaweed to biomedical applications is needed. This encompasses algae culture, extraction, chemistry, characterization, processing, and an understanding of the interactions of soft matter with living organisms. In this review, we present algae polysaccharides that intrinsically form hydrogels: alginate, carrageenan, ulvan, starch, agarose, porphyran, and (nano)cellulose and classify these by their gelation mechanisms. The focus of this review further lays on the culture and extraction strategies to obtain pure polysaccharides, their structure-properties relationships, the current advances in chemical backbone modifications, and how these modifications can be used to tune the polysaccharide properties. The available techniques to characterize each organization scale of a polysaccharide hydrogel are presented, and the impact on their interactions with biological systems is discussed. Finally, a perspective of the anticipated development of the whole field and how the further utilization of hydrogel-forming polysaccharides extracted from algae can revolutionize the current algae industry are suggested.

Hyperstimulation of CaSR in human MSCs by biomimetic apatite inhibits endochondral ossification via temporal down-regulation of PTH1R.

In adult bone injuries, periosteum-derived mesenchymal stem/stromal cells (MSCs) form bone via endochondral ossification (EO), whereas those from bone marrow (BM)/endosteum form bone primarily through intramembranous ossification (IMO). We hypothesized that this phenomenon is influenced by the proximity of MSCs residing in the BM to the trabecular bone microenvironment. Herein, we investigated the impact of the bone mineral phase on human BM-derived MSCs' choice of ossification pathway, using a biomimetic bone-like hydroxyapatite (BBHAp) interface. BBHAp induced hyperstimulation of extracellular calcium-sensing receptor (CaSR) and temporal down-regulation of parathyroid hormone 1 receptor (PTH1R), leading to inhibition of chondrogenic differentiation of MSCs even in the presence of chondroinductive factors, such as transforming growth factor-ß1 (TGF-ß1). Interestingly rescuing PTH1R expression using human PTH fragment (1-34) partially restored chondrogenesis in the BBHAp environment. In vivo studies in an ectopic site revealed that the BBHAp interface inhibits EO and strictly promotes IMO. Furthermore, CaSR knockdown (CaSR KD) disrupted the bone-forming potential of MSCs irrespective of the absence or presence of the BBHAp interface. Our findings confirm the expression of CaSR in human BM-derived MSCs and unravel a prominent role for the interplay between CaSR and PTH1R in regulating MSC fate and the choice of pathway for bone formation.

Autophagy inhibition enhances Matrine derivative MASM induced apoptosis in cancer cells via a mechanism involving reactive oxygen species-mediated PI3K/Akt/mTOR and Erk/p38 signaling.

BACKGROUND: In the quest for new anti-cancer drugs, the drug discovery process has shifted to screening of active ingredients in traditional eastern medicine. Matrine is an active alkaloid isolated from plants of the Sophora genus used in traditional Chinese herbal medicine that exhibits a wide spectrum of biological properties and has a potential as an anti-proliferative agent. In this study, we investigated the anticancer property of MASM, ([(6aS, 10S, 11aR, 11bR, 11cS)210-Methylamino-dodecahydro-3a, 7a-diaza-benzo (de)anthracene-8-thione]), a potent derivative of matrine. METHODS: Four epithelial cancer cell lines representing the dominant cancers, namely: A549 (non-small-cell lung cancer cell line), MCF-7 and MDA-MB-231 (breast cancer cell lines), and Hela (cervical cancer cell line) were employed, and the mechanistic underpinning of MASM-induced apoptosis was investigated using flow cytometry, western blot and immunofluorescence. RESULTS: MASM, induced apoptosis via caspase 3 dependent and independent pathways, and autophagy in all the four cancer cell lines, but post-EMT (epithelial mesenchymal transition) cells showed greater sensitivity to MASM. Scavenging reactive oxygen species using N-acetylcysteine rescued all cancer cell lines from apoptosis and autophagy. Mechanistic analysis revealed that MASM induced autophagy involves inhibition of Akt signaling and the activation of Erk and p38 signaling, and inhibition of autophagy further enhanced the apoptosis induced by MASM. CONCLUSIONS: These results indicate that MASM possesses potency against cancer cells and modulating autophagy during MASM administration could be used to further enhance its therapeutic effects.

Biotin-Avidin-Mediated Capture of Microspheres on Polymer Fibers.

Systems for efficient and selective capture of micro-scale objects and structures have application in many areas and are of particular relevance for selective isolation of mammalian cells. Systems for the latter should also not interfere with the biology of the cells. This study demonstrates the capture of microspheres through orthogonal coupling using biotin (ligand) and (strept)avidin (receptor). Fibrous poly(ethylene terephthalate) (PET) meshes were hydrolyzed under controlled alkaline conditions to obtain activated surfaces with COOH groups allowing for the functionalization of the PET with biotin of various spacer length. The system capture efficiency was optimized by varying the length of spacer presenting the biotin against streptavidin. In a proof of concept experiment, avidin-functionalized microspheres were used as surrogates for cells, and their capture under dynamic conditions including virous mixing and high-flow rate perfusion is demonstrated. Functionalization of PET meshes with biotin conjugated to longest spacer yielded the most efficient capture of microspheres. These preliminary results lay the foundation for the development of biosystems for capture of specific cells under physiologically relevant conditions, using biorthogonal avidin-biotin interactions.

Liposomal Treatment of Cancer Cells Modulates Uptake Pathway of Polymeric Nanoparticles by Altering Membrane Stiffness.

Nanomedicines can be taken up by cells via nonspecific and dynamin-dependent (energy-dependent) clathrin and caveolae-mediated endocytosis. While significant effort has focused on targeting pathway-specific transporters, the role of nanobiophysics in the cell lipid bilayer nanoparticle uptake pathway remains largely unexplored. In this study, it is demonstrated that stiffness of lipid bilayer is a key determinant of uptake of liposomes by mammalian cells. Dynamin-mediated endocytosis (DME) of liposomes is found to correlate with its phase behavior, with transition toward solid phase promoting DME, and transition toward fluidic phase resulting in dynamin-independent endocytosis. Since liposomes can transfer lipids to cell membrane, it is sought to engineer the biophysical properties of the membrane of breast epithelial tumor cells (MD-MBA-231) by treatment with phosphatidylcholine liposomes, and elucidate its effect on the uptake of polymeric nanoparticles. Analysis of the giant plasma membrane vesicles derived from treated cells using flicker spectroscopy reveals that liposome treatment alters membrane stiffness and DME of nanoparticles. Since liposomes have a history of use in drug delivery, localized priming of tumors with liposomes may present a hitherto unexploited means of targeting tumors based on biophysical interactions.

A long-lasting oral preformulation of the angiotensin II AT1 receptor antagonist losartan.

Losartan (Los), a non-peptidic orally active agent, reduces arterial pressure through specific and selective blockade of angiotensin II receptor AT1. However, this widely used AT1 antagonist presents low bioavailability and needs once or twice a day dosage. In order to improve its bioavailability, we used the host: guest strategy based on ß-cyclodextrin (ßCD). The results suggest that Los included in ßCD showed a typical pulsatile release pattern after oral administration to rats, with increasing the levels of plasma of Los. In addition, the inclusion compound presented oral efficacy for 72 h, in contrast to Los alone, which shows antagonist effect for only 6 h. In transgenic (mREN2)L27 rats, the Los/ßCD complex reduced blood pressure for about 6 d, whereas Los alone reduced blood pressure for only 2 d. More importantly, using this host: guest strategy, sustained release of Los for over a week via the oral route can be achieved without the need for encapsulation in a polymeric carrier. The proposed preformulation increased the efficacy reducing the dose or spacing between each dose intake.

Differential uptake of nanoparticles by endothelial cells through polyelectrolytes with affinity for caveolae.

Nanoparticles (NPs) constitute an important medium for the targeted delivery of cancer therapeutics. Targeting of NPs to a specific cell type is traditionally achieved through the modification of the NP surface with peptides, aptamers, or other motifs that specifically recognize a cell-surface receptor, leading to internalization of NPs via clathrin and caveolae-mediated endocytosis. We have discovered that modifying the NP surface with anionic polyelectrolytes of varying lipophilicity can regulate the uptake of lipid NPs by endothelial and epithelial cells. Furthermore, we report the finding that synthetic polyelectrolytes composed of an aromatic sulfonic acid backbone exhibit specific affinity for caveolae of endothelial cells. By exploiting the higher expression of caveolae in endothelial cells in comparison with epithelial cells, a purely physiochemical approach to the targeted uptake of lipid NPs to endothelial cells is demonstrated. The ability to confer preferential affinity for NPs to cell surface domains by varying the charge and lipophilic characteristics of an NP surface offers a general means of achieving targeted delivery without the need for receptor-ligand-type targeting strategies.

Stochastic nanoroughness modulates neuron-astrocyte interactions and function via mechanosensing cation channels.

Extracellular soluble signals are known to play a critical role in maintaining neuronal function and homeostasis in the CNS. However, the CNS is also composed of extracellular matrix macromolecules and glia support cells, and the contribution of the physical attributes of these components in maintenance and regulation of neuronal function is not well understood. Because these components possess well-defined topography, we theorize a role for topography in neuronal development and we demonstrate that survival and function of hippocampal neurons and differentiation of telencephalic neural stem cells is modulated by nanoroughness. At roughnesses corresponding to that of healthy astrocytes, hippocampal neurons dissociated and survived independent from astrocytes and showed superior functional traits (increased polarity and calcium flux). Furthermore, telencephalic neural stem cells differentiated into neurons even under exogenous signals that favor astrocytic differentiation. The decoupling of neurons from astrocytes seemed to be triggered by changes to astrocyte apical-surface topography in response to nanoroughness. Blocking signaling through mechanosensing cation channels using GsMTx4 negated the ability of neurons to sense the nanoroughness and promoted decoupling of neurons from astrocytes, thus providing direct evidence for the role of nanotopography in neuron-astrocyte interactions. We extrapolate the role of topography to neurodegenerative conditions and show that regions of amyloid plaque buildup in brain tissue of Alzheimer's patients are accompanied by detrimental changes in tissue roughness. These findings suggest a role for astrocyte and ECM-induced topographical changes in neuronal pathologies and provide new insights for developing therapeutic targets and engineering of neural biomaterials.

Unravelling a Direct Role for Polysaccharide ß-Strands in the Higher Order Structure of Physical Hydrogels.

The mechanical properties of agarose-derived hydrogels depend on the scaffolding of the polysaccharide network. To identify and quantify such higher order structure, we applied Raman optical activity (ROA)-a spectroscopic technique that is highly sensitive toward carbohydrates-on native agarose and chemically modified agarose in the gel phase for the first time. By spectral global fitting, we isolated features that change as a function of backbone carboxylation (28, 40, 50, 60, 80, and 93 %) from other features that remain unchanged. We assigned these spectral features by comparison to ROA spectra calculated for different oligomer models. We found a 60:40 ratio of double- and single-stranded α-helix in the highly rigid hydrogel of native agarose, while the considerably softer hydrogels made from carboxylated agarose use a scaffold of unpaired ß-strands.

Recapitulating epithelial tumor microenvironment in vitro using three dimensional tri-culture of human epithelial, endothelial, and mesenchymal cells.

BACKGROUND: Three-dimensional (3-D) cultures of cancer cells can potentially bridge the gap between 2-D drug screening and in vivo xenografts. The objective of this study was to characterize the cellular and extracellular matrix characteristics of spheroids composed of human lung epithelial cells (epi), pulmonary vascular endothelial (endo) cells, and human marrow-derived mesenchymal stems cells (MSCs). METHODS: Spheroids composed of epi/endo/MSCs, termed herein as synthetic tumor microenvironment mimics (STEMs), were prepared by the hanging drop method. Cellular composition and distribution in the STEMs was characterized using fluorescence microscopy. Induction of reactive oxygen species and upregulation of efflux transporters was quantified using fluorometry and PCR, respectively, and phenotypic markers were qualitatively assessed using immunohistochemistry. RESULTS: STEMs exhibited three unique characteristics not captured in other spheroid cultures namely, the presence of a spheroid core devoid of epithelial cells and primarily composed of MSCs, a small viable population of endothelial cells hypothesized to be closely associated with MSCs within the hypoxic core, and discrete regions with high expression for vimentin and cytokeratin-18, whose co-expression is co-related with enhanced metastasis. Although cells within STEMs show elevated levels of reactive oxygen species and mRNA for ABC-B1, an efflux transporter associated with drug resistance, they exhibited only modest resistance to paclitaxel and gemcitabine in comparison to 2-D tri-cultures. CONCLUSIONS: The epi/endo/MSC spheroid model described herein offers a promising platform for understanding tumor biology and drug testing in vitro.

Nanofibers of Elastin and Hydrophilic Segmented Polyurethane Solution Blends Show Enhanced Mechanical Properties through Intermolecular Protein-Polymer H Bonding.

Combining mechanical properties with enhanced cell interaction is highly desirable in a biomaterial. In this study, a new paradigm for enhancing the mechanical properties of segmented polyurethanes (SPUs) through solution blending with a biopolymer is presented. This noncovalent approach is based on the premise that molecular level blending of SPUs rich in hydrogen bonding (H bonding) domains with a biopolymer capable of H bonding will promote H-bond bridges between the components, leading to molecular annealing and modification of the physicochemical properties of the SPU. We demonstrate that by solution-blending solubilized elastin with a triblock copolymer-derived SPU, a 5-fold increase in tensile modulus of electrospun constructs of the SPU can be achieved, with concomitant enhancement in human endothelial cell attachment. Spectroscopic and calorimetric analysis confirm the role of H bonding in the enhancement, thus providing the impetus to further explore blending with biopolymers as a means of improving the property profiles of synthetic polymeric biomaterials.

Albumin Incorporation in Polyethylenimine-DNA Polyplexes Influences Transfection Efficiency.

Polyplexes of plasmid with synthetic polycationic vectors, such as linear polyethylenimine (LPEI), have been widely investigated. While much is known about the role of physicochemical characterization of the polycation in transfection, the role of serum components in the transfection using LPEI-polyplexes needs further investigation. In this study, bovine serum albumin was incorporated into the polyplex, either through precomplexation with circular DNA coding for green fluorescent protein prior to polyplex formation with LPEI or after formation of the polyplex. The transfection efficiency of these ternary polyplexes was then studied in HeLa cells. It was observed that the order of incorporation of albumin into polyplexes has a distinct effect on its uptake and transfection efficiency. Through colocalization and albumin depletion studies, we conclude that albumin plays a role in both the translocation of the complex into the cell and its unpackaging.

Nonwoven Carboxylated Agarose-Based Fiber Meshes with Antimicrobial Properties.

Hydrogel forming polysaccharides, such as the seaweed derived agarose, are well suited for wound dressing applications as they have excellent cell and soft tissue compatibility. For wound dressings, fibrous structure is desirable as the high surface area can favor adsorption of wound exudate and promote drug delivery. Although electrospinning offers a straightforward means to produce nonwoven fibrous polymeric structures, processing agarose and its derivatives into fibers through electrospinning is challenging as it has limited solubility in solvents other than water. In this study we describe the processing of carboxylated agarose (CA) fibers with antibacterial properties by electrospinning from a solution of the ionic liquid (IL) 1-butyl-3-methylimidazolium chloride ([Bmim]+Cl-) possessing antimicrobial properties. The extent of carboxylation was found to impact fiber diameter, mesh elastic modulus, fiber swelling, and the loading and release of IL. IL-bearing CA fibers inhibited the growth of Staphylococcus aureus and Pseudomonas aeruginosa, bacteria commonly found in wound exudate. In sum, nonwoven CA fibers processed from IL are promising as biomaterials for wound dressing applications.

Polysaccharide hydrogels with tunable stiffness and provasculogenic properties via α-helix to ß-sheet switch in secondary structure.

Mechanical aspects of the cellular environment can influence cell function, and in this context hydrogels can serve as an instructive matrix. Here we report that physicochemical properties of hydrogels derived from polysaccharides (agarose, κ-carrageenan) having an α-helical backbone can be tailored by inducing a switch in the secondary structure from α-helix to ß-sheet through carboxylation. This enables the gel modulus to be tuned over four orders of magnitude (G' 6 Pa-3.6 × 10(4) Pa) independently of polymer concentration and molecular weight. Using carboxylated agarose gels as a screening platform, we demonstrate that soft-carboxylated agarose provides a unique environment for the polarization of endothelial cells in the presence of soluble and bound signals, which notably does not occur in fibrin and collagen gels. Furthermore, endothelial cells organize into freestanding lumens over 100 µm in length. The finding that a biomaterial can modulate soluble and bound signals provides impetus for exploring mechanobiology paradigms in regenerative therapies.

Mechanically tailored agarose hydrogels through molecular alloying with ß-sheet polysaccharides.

There is mounting evidence that the mechanical property of tissues provides important cues that control cell fate. However, implementation of hydrogels with tunable physicochemical properties is limited due to the challenges associated with crosslinking chemistries. It has been recently shown that mechanically well-defined injectable polysaccharide hydrogels can be engineered by switching their secondary structure from an α-helix to a ß-sheet. Based on these findings, a new concept is presented to tailor the mechanical properties of agarose hydrogels via the blending with the ß-sheet-rich carboxylated derivative. Using this simple strategy, gels with predictable roughness, fiber organization, and shear modulus ranging from 0.1 to 100 kPa can be formulated. Hydrogels whose mechanical properties can be precisely tailored in vivo without the recourse for chemical reactions are expected to play an important role in implementing mechanobiology paradigms in de novo tissue engineering.

Glycosylation facilitates transdermal transport of macromolecules.

Stratum corneum, the outermost layer of skin, allows transport of only low-molecular weight (<500) lipophilic solutes. Here, we report a surprising finding that avicins (Avs), a family of naturally occurring glycosylated triterpenes with a molecular weight > 2,000, exhibit skin permeabilities comparable to those of small hydrophobic molecules, such as estradiol. Systematic fragmentation of the Av molecule shows that deletion of the outer monoterpene results in a 62% reduction in permeability, suggesting an important role for this motif in skin permeation. Further removal of the tetrasaccharide residue results in a further reduction of permeability by 79%. These results, taken in sum, imply that synergistic effects involving both hydrophobic and hydrophilic residues may hold the key in facilitating translocation of Avs across skin lipids. In addition to exhibiting high permeability, Avs provided moderate enhancements of skin permeability of estradiol and polysaccharides, including dextran and inulin but not polyethylene glycol.

Cyclic comonomers for the synthesis of carboxylic acid and amine functionalized poly(L-lactic acid).

Degradable aliphatic polyesters such as poly(lactic acid) are widely used in biomedical applications, however, they lack functional moieties along the polymer backbone that are amenable for functionalization reactions or could be the basis for interactions with biological systems. Here we present a straightforward route for the synthesis of functional α-ω epoxyesters as comonomers for lactide polymerization. Salient features of these highly functionalized epoxides are versatility in functionality and a short synthetic route of less than four steps. The α-ω epoxyesters presented serve as a means to introduce carboxylic acid and amine functional groups into poly(lactic acid) polymers via ring-opening copolymerization.