The development of collagen hydrogels with tailored properties for improved applications in biomedicine represents an area of opportunity for materials science. The collagen can form ...semi‐interpenetrated networks (semi‐IPN) with various natural and/or synthetic polymers. This work aims the preparation of novel hydrogels generated from a collagen matrix cross‐linked with polyurethane (PU), and the subsequent inclusion of polysaccharide chains to form semi‐IPN systems with improved properties. The choice of polysaccharides for this purpose is related to their ability to modulate the biocompatibility and the antibacterial capacity in various biomedical strategies. The work contemplates to study the effect of the chemical structure of polysaccharide (hydroxyethylcellulose (HEC), hydroxypropylmethylcellulose (HPMC) or starch (Alm)) on the properties of these novel hydrogels. The results indicate that the semi‐IPN hydrogels that include Alm exhibit the formation of stronger intermolecular interactions promoted by hydrogen bonds than HEC and HPMC, significantly improving the mechanical properties and their degradation rate in acidic, alkaline, and proteolytic media; also showing high capacity to inhibit the growth of E. colli. The semi‐IPN hydrogels based on HEC and HPMC exhibit excellent improvement in both thermal and proteolytic degradation, compared with the collagen‐PU matrix. On the other hand, this semi‐IPN system does not present cytotoxic character for monocytes and fibroblasts growing for up to 48 h of culture. Therefore, these innovative 3D matrices will be excellent candidates with potential application in biomedical strategies such as wound healing dressings.
In this work, hydrogels based on semi‐interpenetrating polymeric networks (semi‐IPN) based on collagen‐polyurethane‐alginate were studied physicochemically and from different approaches for ...biomedical application. It was determined that the matrices in the hydrogel state are crosslinked by the formation of urea and amide bonds between the biopolymer chains and the polyurethane crosslinker. The increment in alginate content (0–40 wt%) significantly increases the swelling capacity, generating semi‐crystalline granular structures with improved storage modulus and resistance to thermal, hydrolytic, and proteolytic degradation. The in vitro bioactivity results indicated that the composition of these novel hydrogels stimulates the metabolic activity of monocytes and fibroblasts, benefiting their proliferation; while in cancer cell lines, it was determined that the composition of these biomaterials decreases the metabolic activity of breast cancer cells after 48 h of stimulation, and for colon cancer cells their metabolic activity decreases after 72 h of contact for the hydrogel with 40 wt% alginate. The matrices show a behavior of multidose release of ketorolac, and a higher concentration of analgesic is released in the semi‐IPN matrix. The inhibition capacity of Escherichia coli is higher if the polysaccharide concentration is low (10 wt%). The in vitro wound closure test (scratch test) results indicate that the hydrogel with 20 wt% alginate shows an improvement in wound closure at 15 days of contact. Finally, the bioactivity of mineralization was evaluated to demonstrate that these hydrogels can induce the formation of carbonated apatite on their surface. The engineered hydrogels show biomedical multifunctionality and they could be applied in soft and hard tissue healing strategies, anticancer therapies, and drug release devices.
Voltage controlled voltage source converters (VCVSC) and current controlled voltage source converters (CCVSC) have gained importance within distributed power generation systems and equipment for ...power quality improvement. The control action is susceptible to fall in saturation under disturbance transients or in case of poor control tuning. The use of existing saturation techniques for vector variables, such as three-phase voltage and current, distorts the reference waveforms under unbalanced conditions regardless the used reference frames--stationary (αβ-axis) or synchronous (dq-axis). These harmonics are quite detrimental for the electric grid and reduce the efficiency. This paper presents a distortion-free saturation methodology with two versions and analyzes the performance in function of the control structure (VCVSC and CCVSC) and the saturation point within the control loop. The experimental results prove the advantages of using the proposed saturators.
This work studied the effect of content of starch on the structure and properties of hydrogels generated by semi-interpenetrating the polysaccharide in the collagen-polyurethane matrix and generating ...biomaterials in the hydrogel state potentially useful in biomedicine. Starch increased the reticulation of the polymeric matrix by hydrogen bonding with the collagen fibers. The maximum swelling degree was observed for the formulation containing 40 wt.% of starch. The microstructure of these materials is semi-crystalline and the increase of the content of starch avoids the segregation of starch granules in the matrix, generating homogeneous surfaces that tend to release less glucose-rich degradation by-products and encapsulated ketorolac. Materials with low content of starch (10-20 wt.%) improve both the mechanical and thermal stability of the hydrogels and the ketorolac release performance. The matrices activated the metabolism of monocytes and fibroblasts, favoring their proliferation. The presence of starch in semi-IPN hydrogels confers high inhibition capacity of E. coli and a slow rate of hydrolytic and proteolytic degradation. The results of cell signaling for important cytokines in the wound healing process indicated that the CS20% matrix shows favorable modulation of TNF-α, MCP-1, and TGF-β secretion, so it could be successfully applied in the treatment of chronic wounds.
In this paper, a space-vector discrete-time Fourier transform is proposed for fast and precise detection of the fundamental-frequency and harmonic positive- and negative-sequence vector components of ...three-phase input signals. The discrete Fourier transform is applied to the three-phase signals represented by Clarke's αβ vector. It is shown that the complex numbers output from the Fourier transform are the instantaneous values of the positive- and negative-sequence harmonic component vectors of the input three-phase signals. The method allows the computation of any desired positive- or negative-sequence fundamental-frequency or harmonic vector component of the input signal. A recursive algorithm for low-effort online implementation is also presented. The detection performance for variable-frequency and interharmonic input signals is discussed. The proposed and other usual method performances are compared through simulations and experiments.
Developing new approaches to improve the swelling, degradation rate, and mechanical properties of alginate hydrogels without compromising their biocompatibility for biomedical applications represents ...a potential area of research. In this work, the generation of interpenetrated networks (IPN) comprised from alginate–polyurethane in an aqueous medium is proposed to design hydrogels with tailored properties for biomedical applications. Aqueous polyurethane (PU) dispersions can crosslink and interpenetrate alginate chains, forming amide bonds that allow the structure and water absorption capacity of these novel hydrogels to be regulated. In this sense, this work focuses on studying the relation of the PU concentration on the properties of these hydrogels. The results indicate that the crosslinking of the alginate with PU generates IPN hydrogels with a crystalline structure characterized by a homogeneous smooth surface with high capacity to absorb water, tailoring the degradation rate, thermal decomposition, and storage module, not altering the native biocompatibility of alginate, providing character to inhibit the growth of
E. coli
and increasing also its hemocompatibility. The IPN hydrogels that include 20 wt.% of PU exhibit a reticulation index of 46 ± 4%, swelling capacity of 545 ± 13% at 7 days of incubation at physiological pH, resistance to both acidic and neutral hydrolytic degradation, mechanical improvement of 91 ± 1%, and no cytotoxicity for monocytes and fibroblasts growing for up to 72 h of incubation. These results indicate that these novel hydrogels can be used for successful biomedical applications in the design of wound healing dressings.
Wound healing is a biological process that requires a complex regulation to maintaining the function of skin. However, many factors can alter this process, resulting in non-healing wounds. An option ...for the treatment of this kind of wound is the use of stem cell secretome (S), since it has been shown that it promotes the tissue repair-regeneration processes. For this reason, this work focused on develop a polymeric matrix in hydrogel state, based on jellyfish collagen (CLG), polyurethane and S from mesenchymal stem cells (MSCs) from human amniotic membrane, and its in vitro evaluation in wound closure. Two types of polyurethane matrix were analyzed; the first one was crosslinking with polyurethane derived from hexamethylene diisocyanate (HDI), and the second one was crosslinking with polyurethane derived from isophorone diisocyanate (IPDI), giving rise to two different polymeric matrices, CLG-P(HDI)-S and CLG-P(IPDI)-S containing 0.5 wt.% of S for each matrix. The results suggest that the incorporation to S in the polymeric matrices generates interactions in the hydrogel state matrices, promoting amorphous surfaces, which seems to indicate that the S is encapsulated by physical or electrostatic interactions with polymeric chains. The CLG-P(HDI)-S showed a spherical structure, while the CLG-P(IPDI)-S exhibited a planar structure, which is related to the chemical structure of polyurethane crosslinker, these structural characteristics gave the polymeric matrices, suitable physicochemical, mechanical and biological properties for accelerating the wound healing process in an in vitro scratch assay, and thus could be a promising scaffold for wound management for non-healing wounds.
Graphical abstract
The design of hydrogels based on natural polymers that have modulation of antibacterial capacity, ideal performance in release capacity of encapsulated drugs, and desired bioactivity for applications ...in wound healing represents a modern trend in biomaterials. In this work, novel hydrogels of semi-interpenetrating polymeric networks based on collagen and xanthan gum (XG) were investigated. The linear chains of XG can semi-interpenetrate inside to matrix of crosslinked collagen with polyurethane under physiological conditions, generating amorphous surfaces with fibrillar-granular reliefs that have accelerated gelation time (about 15 min), super water absorption (up to 3100%) and high inhibition capacity of pathogenic bacteria such as
(up to 100% compared to amoxicillin at 20 ppm). The increment of XG in the hydrogel (up to 20 wt.%) allows for improvement in the storage module, resistance to thermal degradation, slow the rate of hydrolytic and proteolytic degradation, allowing to encapsulate and controlled release of molecules such as ketorolac and methylene blue; besides, it shows to keep the metabolic activity of fibroblasts and monocytes at 48 h of evaluation, without observing cytotoxic effects. The bioactivity of these hydrogels is improved since they have excellent hemocompatibility and enhanced cell proliferation. Specifically, the hydrogel with 20 wt.% of XG shows to decrease the production of tumor necrosis factor-
and CCL-2 cytokines, increasing the production of transforming growth factor-
in human monocytes, which could be used to modulate inflammation and regenerative capacity in wound healing strategies.
The modification of collagen derived from jellyfish to generate hydrogels with high biocompatibility is in recent trend, since this type of collagen does not present allergenic effects or ...transmission of zoonosis in humans. Therefore, developing novel strategies that allow tailoring their properties for regenerative medicine and biomedical applications is a current research challenge. In this work, the generation of interpenetrating polymeric matrices (IPN) in the hydrogel state composed of jellyfish collagen (
C. andromeda
) and polyurethane is proposed; for this, dispersions of trifunctional polyurethane prepolymers (TPU) derived from glycerol ethoxylate and hexamethylene diisocyanate (P(HDI)) or isophorone diisocyanate (P(IPDI)) are used as interpenetrating agents for marine collagen chains. The evaluation of the structural modification produced by the chemical structure of the TPU on the properties and the in vitro biocompatibility of the matrices in the hydrogel state is addressed. The results indicate that IPN hydrogels based on P(HDI) show a structure based on microspheric agglomerates with interconnected porosity, while those generated from P(IPDI) exhibit a smooth structure with irregular porosity. The interpenetration of jellyfish collagen with P(HDI) produces an improvement in the storage modulus of 16,972%, enhancing the swelling in acidic, physiological and basic media; as well as delaying proteolytic degradation. Both novel matrices do not present cytotoxic effects for monocytes and fibroblasts, evaluated for up to 48 h of incubation, indicating that they have excellent in vitro biocompatibility, in addition they present enhanced hemocompatility and capacity to inhibit the growth of
E. coli
; due to this, these matrices in hidrogel state can be applied in strategies for the design of dressings for regenerative medicine applications.
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