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Papers by Timothy Douglas

Interest is growing in the use of hydrogels as bone tissue-engineering (TE) scaffolds due to adva... more Interest is growing in the use of hydrogels as bone tissue-engineering (TE) scaffolds due to advantages such as injectability and ease of incorporation of active substances such as enzymes. Hydrogels consisting of gellan gum (GG), an inexpensive calcium-crosslinkable polysaccharide, have been applied in cartilage TE. To improve GG suitability as a material for bone TE, alkaline phosphatase (ALP), an enzyme involved in mineralization of bone by cleaving phosphate from organic phosphate, was incorporated into GG hydrogels to induce mineralization with calcium phosphate (CaP). Incorporated ALP induced formation of apatite-like material on the submicron scale within GG gels, as shown by FTIR, SEM, EDS, XRD, ICP-OES, TGA and von Kossa staining. Increasing ALP concentration increased amounts of CaP as well as stiffness. Mineralized GG was able to withstand sterilization by autoclaving, although stiffness decreased. In addition, mineralizability and stiffness of GG was enhanced by the incorporation of polydopamine (PDA). Furthermore, mineralization of GG led to enhanced attachment and vitality of cells in vitro while cytocompatibility of the mineralized gels was comparable to one of the most commonly used bone substitute materials. The results proved that ALP-mediated enzymatic mineraliza-tion of GG could be enhanced by functionalization with PDA.

Thermosensitive injectable hydrogels based on chitosan neutralized with sodium beta-glycerophosph... more Thermosensitive injectable hydrogels based on chitosan neutralized with sodium beta-glycerophosphate (Na-β-GP) have been studied as biomaterials for drug delivery and tissue regeneration. Magnesium (Mg) has been reported to stimulate adhesion and proliferation of bone forming cells. With the aim of improving the suitability of the aforementioned chitosan hydrogels as materials for bone regeneration, Mg was incorporated by partial substitution of Na-β-GP with magnesium glycerophosphate (Mg-GP). Chitosan/Na-β-GP and chitosan/Na-β-GP/Mg-GP hydrogels were also loaded with the enzyme alkaline phosphatase (ALP) which induces hydrogel mineralization. Hydrogels were characterized physicochemically with respect to mineralizability and gelation kinetics, and biologically with respect to cytocompatibility and cell adhesion. Substitution of Na-β-GP with Mg-GP did not negatively influence mineralizability. Cell biological testing showed that both chitosan/Na-β-GP and chitosan/Na-β-GP/Mg-GP hydrogels were cytocompatible towards MG63 osteoblast-like cells. Hence, chitosan/Na-β-GP/Mg-GP hydrogels can be used as an alternative to chitosan/Na-β-GP hydrogels for bone regeneration applications. However the incorporation of Mg in the hydrogels during hydrogel formation did not bring any appreciable physicochemical or biological benefit.

Novel injectable, self-gelling hydrogel–microparticle composites for bone regeneration consisting... more Novel injectable, self-gelling hydrogel–microparticle composites for bone regeneration consisting of gellan gum and calcium and magnesium carbonate microparticles

Thermosensitive injectable chitosan hydrogels can be formed by neutralization of acidic chitosan ... more Thermosensitive injectable chitosan hydrogels can be formed by neutralization of acidic chitosan solutions with sodium beta-glycerophosphate (Na-β-GP) coupled with increasing temperature to body temperature. Such hydrogels have been considered for applications in bone regeneration. In this study, chitosan hydrogels were enriched with glycerol and the enzyme alkaline phosphatase (ALP) with a view to improving their suitability as materials for bone tissue engineering. Mineral formation was confirmed by infrared spec-troscopy (FTIR) and increases in the mass fraction of the hydrogel not consisting of water. Incorporation of ALP in hydrogels followed by incubation in a solution containing calcium ions and glycerophosphate, a substrate for ALP, led to formation of calcium phosphate within the hydrogel. MG-63 osteoblast-like cells were cultivated in eluates from hydrogels containing ALP and without ALP at different dilutions and directly on the hydrogel samples. Hydrogels containing ALP exhibited superior cytocompatibility to ALP-free hydrogels. These results pave the way for the use of glycerol-and ALP-enriched hydrogels in bone regeneration.

Mineralization of hydrogel biomaterials is considered desirable to improve their suitability as m... more Mineralization of hydrogel biomaterials is considered desirable to improve their suitability as materials for bone regeneration. Calcium carbonate (CaCO 3) has been successfully applied as a bone regeneration material, but hydrogel-CaCO 3 composites have received less attention. Magnesium (Mg) has been used as a component of calcium phosphate biomaterials to stimulate bone-forming cell adhesion and proliferation and bone regeneration in vivo, but its effect as a component of carbonate-based biomaterials remains uninvestigated. In the present study, gellan gum (GG) hydrogels were mineralized enzymatically with CaCO 3 , Mg-enriched CaCO 3 and magnesium carbonate to generate composite biomaterials for bone regeneration. Hydrogels loaded with the enzyme urease were mineralized by incubation in mineralization media containing urea and different ratios of calcium and magnesium ions. Increasing the magnesium concentration decreased mineral crystallinity. At low magnesium concentrations calcite was formed, while at higher concentrations magnesian calcite was formed. Hydromagnesite (Mg 5 (CO 3) 4 (OH) 2 .4H 2 O) formed at high magnesium concentration in the absence of calcium. The amount of mineral formed and compressive strength decreased with increasing magnesium concentration in the mineralization medium. The calcium: magnesium elemental ratio in the mineral formed was higher than in the respective mineralization media. Mineralization of hydrogels with calcite or magnesian calcite promoted adhesion and growth of osteoblast-like cells. Hydrogels mineralized with hydromagnesite displayed higher cytotoxicity. In conclusion, enzymatic mineralization of GG hydrogels with CaCO 3 in the form of calcite successfully reinforced hydrogels and promoted osteoblast-like cell adhesion and growth, but magnesium enrichment had no definitive positive effect.

Hydrogels are popular materials for tissue regeneration. Incorporation of biologically active sub... more Hydrogels are popular materials for tissue regeneration. Incorporation of biologically active substances, e.g. enzymes, is straightforward. Hydrogel mineralization is desirable for bone regeneration. Here, hydro-gels of Gellan Gum (GG), a biocompatible polysaccharide, were mineralized biomimetically with CaCO 3 using a double enzymatic approach. The enzymes urease (U) and carbonic anhydrase (CA) were incorporated in GG hydrogels. Hydrogels were incubated in a mineralization solution containing U substrate (urea) and calcium ions. U converts urea to ammonia (which raises pH) and CO 2. CA catalyses the reaction of CO 2 with water to form HCO 3 À , which undergoes deprotonation to form CO 3 2À , which react with Ca 2+ to form insoluble CaCO 3. All hydrogels containing U+CA were mineralized more with calcite and stiffer than hydrogels containing U. Mineralization with calcite promoted proliferation and spreading of osteoblast-like cells.

Injectable self-gelling composites for bone tissue engineering based on gellan gum hydrogel enric... more Injectable self-gelling composites for bone tissue engineering based on gellan gum hydrogel enriched with different bioglasses Timothy E L Douglas, Wojciech Piwowarczyk, Elzbieta Pamula et al. Novel injectable, self-gelling hydrogel-microparticle composites for bone regeneration consisting of gellan gum and calcium and magnesium carbonate microparticles Timothy E L Douglas, Agata apa, Katarzyna Reczyska et al. Towards antimicrobial yet bioactive Cu-alginate hydrogels I Madzovska-Malagurski, M Vukasinovic-Sekulic, D Kostic et al. High performance bio-based hyperbranched polyurethane/carbon dot-silver nanocomposite: a rapid self-expandable stent Rituparna Duarah, Yogendra P Singh, Prerak Gupta et al. Injectable osteogenic and angiogenic nanocomposite hydrogels for irregular bone defects M Vishnu Priya, A Sivshanmugam, A R Boccaccini et al.

Coating biomedical implant surfaces with biopolymers is an easy and inexpensive way to impart fun... more Coating biomedical implant surfaces with biopolymers is an easy and inexpensive way to impart func-tionalities. Numerous biocompatible biopolymers, including cationic crustacean-derived chitosans, have been used. Here, substrates of Titanium (Ti), commonly used for bone contact applications, were coated with chitosan and one of three polyphenol-rich plant extracts (PPrPE) and characterized physicochemi-cally. Hela cell adhesion and growth of methicillin-resistant Staphylococcus aureus (MRSA) were studied. Chitosan and PPrPE on surfaces were detected by FTIR and XPS. Chitosan coatings, both with and without PPrPE functionalization, did not inhibit MRSA growth and promoted Hela cell adhesion. The effect of PPrPE functionalization remained unclear.

Biochemistry Research International, 2012

Acta of bioengineering and biomechanics / Wrocław University of Technology, 2016

Thermosensitive injectable chitosan hydrogels can be formed by neutralization of acidic chitosan ... more Thermosensitive injectable chitosan hydrogels can be formed by neutralization of acidic chitosan solutions with sodium betaglycerophosphate (Na-β-GP) coupled with increasing temperature to body temperature. Such hydrogels have been considered for applications in bone regeneration. In this study, chitosan hydrogels were enriched with glycerol and the enzyme alkaline phosphatase (ALP) with a view to improving their suitability as materials for bone tissue engineering. Mineral formation was confirmed by infrared spectroscopy (FTIR) and increases in the mass fraction of the hydrogel not consisting of water. Incorporation of ALP in hydrogels followed by incubation in a solution containing calcium ions and glycerophosphate, a substrate for ALP, led to formation of calcium phosphate within the hydrogel. MG-63 osteoblast-like cells were cultivated in eluates from hydrogels containing ALP and without ALP at different dilutions and directly on the hydrogel samples. Hydrogels containing ALP ex...

Biomedical materials (Bristol, England), 2016

Hydrogels offer several advantages as biomaterials for bone regeneration, including ease of incor... more Hydrogels offer several advantages as biomaterials for bone regeneration, including ease of incorporation of soluble substances such as mineralization-promoting enzymes and antibacterial agents. Mineralization with calcium phosphate (CaP) increases bioactivity, while antibacterial activity reduces the risk of infection. Here, gellan gum (GG) hydrogels were enriched with alkaline phosphatase (ALP) and/or Seanol(®), a seaweed extract rich in phlorotannins (brown algae-derived polyphenols), to induce mineralization with CaP and increase antibacterial activity, respectively. The sample groups were unmineralized hydrogels, denoted as GG, GG/ALP, GG/Seanol and GG/Seanol/ALP, and hydrogels incubated in mineralization medium (0.1 M calcium glycerophosphate), denoted as GG/ALP_min, GG/Seanol_min and GG/Seanol/ALP_min. Seanol(®) enhanced mineralization with CaP and also increased compressive modulus. Seanol(®) and ALP interacted in a non-covalent manner. Release of Seanol(®) occurred in a bur...

Materials Letters, Oct 28, 2015

In the current study, the effect of post-plasma grafting of 2-aminoethyl methacrylate (AEMA) and ... more In the current study, the effect of post-plasma grafting of 2-aminoethyl methacrylate (AEMA) and the subsequent covalent immobilization of gelatin (GelB) on poly(L-lactide-co-glycolide) (PLGA) thin films were investigated. The applied modification resulted in surface chemistry changes of PLGA. More specifically, an increase of nitrogen from 0 at% to 14 at% with a concomitant decrease in carbon and oxygen concentration was observed. The samples were more hydrophilic after the treatment as reflected by a decrease of the water contact angle from 721 to 331 and more rough at the nanoscale as shown by atomic force microscopy (increase of R a roughness from 0.7 nm to 10 nm). The growth of osteoblast-like MG-63 cells was enhanced on biofunctionalised PLGA-AEMA-GelB surfaces and the cells were more homogenously distributed than on non-modified PLGA. Our findings are especially important for tissue engineering applications, where substrates supporting homogenous cell cultures are particularly promising.

The International Journal of Oral Maxillofacial Implants, 2011

Purpose: Human mesenchymal stem cells (hMSCs) hold the potential for bone regeneration because of... more Purpose: Human mesenchymal stem cells (hMSCs) hold the potential for bone regeneration because of their self-renewing and multipotent character. The goal of this study was to evaluate the influence of collagen membranes on the proliferation of hMSCs derived from bone marrow. A special focus was set on short-term eluates derived from collagen membranes, as volatile toxic materials washed out from these membranes may influence cell behavior during the short time course of oral surgery. Materials and Methods: The proliferation of hMSCs seeded directly on a collagen membrane (BioGide) was evaluated quantitatively using the cell proliferation reagent were performed using hMSCs cultivated in eluates from membranes incubated for 10 minutes, 1 hour, or 24 hours in serum-free cell culture medium. The data were analyzed statistically. Results: Scanning electron microscopy showed large numbers of hMSCs with well-spread morphology on the collagen membranes after 7 days of culture. The WST test revealed significantly better proliferation of hMSCs on collagen membranes after 4 days of culture compared to cells cultured on a cover glass. Cytotoxicity levels were low, peaking in short-term eluates and decreasing with longer incubation times. Conclusion: Porcine collagen membranes showed good biocompatibility in vitro for hMSCs. If maximum cell proliferation rates are required, a prewash of membranes prior to application may be useful. Int J Oral MaxIllOfac IMplants 2011;26:1004-1010

Journal of biomedical materials research. Part A, Jan 7, 2016

Enrichment of hydrogels with inorganic particles improves their suitability for bone regeneration... more Enrichment of hydrogels with inorganic particles improves their suitability for bone regeneration by enhancing their mechanical properties, mineralizability and bioactivity as well as adhesion, proliferation and differentiation of bone-forming cells, while maintaining injectability. Low aggregation and homogeneous distribution maximize particle surface area, promoting mineralization, cell-particle interactions and homogenous tissue regeneration. Hence, determination of the size and distribution of particles/particle agglomerates in the hydrogel is desirable. Commonly used techniques have drawbacks. High-resolution techniques (e.g. SEM) require drying. Distribution in the dry state is not representative of the wet state. Techniques in the wet state (histology, µCT) are of lower resolution. Here, self-gelling, injectable composites of Gellan Gum (GG) hydrogel and two different types of sol-gel derived bioactive glass (bioglass) particles were analyzed in the wet state using Synchrotro...

Journal of Tissue Engineering and Regenerative Medicine, 2015

Gellan gum hydrogels functionalized with alkaline phosphatase were enzymatically mineralized with... more Gellan gum hydrogels functionalized with alkaline phosphatase were enzymatically mineralized with phosphates in mineralization medium containing calcium (Ca) and zinc (Zn) to improve their suitability as biomaterials for bone regeneration. The aims of the study were to endow mineralized hydrogels with antibacterial activity by incorporation of Zn in the inorganic phase, and to investigate the effect of Zn incorporation on the amount and type of mineral formed, the compressive modulus of the mineralized hydrogels and on their ability to support adhesion and growth of MC3T3-E1 osteoblast-like cells. Mineralization medium contained glycerophosphate (0.05 m) and three different molar Ca:Zn ratios, 0.05:0, 0.04:0.01 and 0.025:0.025 (all mol/dm(3) ), hereafter referred to as A, B and C, respectively. FTIR, SAED and TEM analysis revealed that incubation for 14 days caused the formation of predominantly amorphous mineral phases in sample groups A, B and C. The presence of Zn in sample groups B and C was associated with a drop in the amount of mineral formed and a smaller mineral deposit morphology, as observed by SEM. ICP-OES revealed that Zn was preferentially incorporated into mineral compared to Ca. Mechanical testing revealed a decrease in compressive modulus in sample group C. Sample groups B and C, but not A, showed antibacterial activity against biofilm-forming, methicillin-resistant Staphylococcus aureus. All sample groups supported cell growth. Zn incorporation increased the viable cell number. The highest values were seen on sample group C. In conclusion, the sample group containing the most Zn, i.e. group C, appears to be the most promising. Copyright © 2015 John Wiley & Sons, Ltd.

Carbohydrate Polymers, 2015

Injectable hydrogels for bone regeneration consisting of chitosan, sodium beta-glycerophosphate (... more Injectable hydrogels for bone regeneration consisting of chitosan, sodium beta-glycerophosphate (Na-␤-GP) and alkaline phosphatase (ALP) were enriched with the polyphenols phloroglucinol (PG) and gallic acid (GA) and characterized physicochemically and biologically with respect to properties relevant for applications in bone regeneration, namely gelation kinetics, mineralizability, antioxidant properties, antibacterial activity, cytocompatibility and ability to support adhesion and growth of human osteoblast-like MG63 cells. Enrichment with PG and GA had no negative effect on gelation kinetics and mineralizability. PG and GA both enhanced antioxidant activity of unmineralized hydrogels. Mineralization reduced antioxidant activity of hydrogels containing GA. Hydrogels containing GA, PG and without polyphenols reduced colony forming ability of Escherichia coli after 1 h, 3 h and 6 h incubation and slowed E. coli growth in liquid culture for 150 min. Hydrogels containing GA were cytotoxic and supported cell growth more poorly than polyphenol-free hydrogels. PG had no negative effect on cell adhesion and growth.

The International journal of oral & maxillofacial implants

Human mesenchymal stem cells (hMSCs) hold the potential for bone regeneration because of their se... more Human mesenchymal stem cells (hMSCs) hold the potential for bone regeneration because of their self-renewing and multipotent character. The goal of this study was to evaluate the influence of collagen membranes on the proliferation of hMSCs derived from bone marrow. A special focus was set on short-term eluates derived from collagen membranes, as volatile toxic materials washed out from these membranes may influence cell behavior during the short time course of oral surgery. The proliferation of hMSCs seeded directly on a collagen membrane (BioGide) was evaluated quantitatively using the cell proliferation reagent WST-1 (4-3-[4-iodophenyl]-2-[4-nitrophenyl]-2H-[5-tetrazolio]-1, 3--benzol-disulfonate) and qualitatively by scanning electron microscopy. Two standard biocompatibility tests, namely the lactate dehydrogenase and MTT (3-[4, 5-dimethyl-2-thiazolyl]-2, 5-diphenyl-2H-tetrazoliumbromide) tests, were performed using hMSCs cultivated in eluates from membranes incubated for 10 mi...

Interest is growing in the use of hydrogels as bone tissue-engineering (TE) scaffolds due to adva... more Interest is growing in the use of hydrogels as bone tissue-engineering (TE) scaffolds due to advantages such as injectability and ease of incorporation of active substances such as enzymes. Hydrogels consisting of gellan gum (GG), an inexpensive calcium-crosslinkable polysaccharide, have been applied in cartilage TE. To improve GG suitability as a material for bone TE, alkaline phosphatase (ALP), an enzyme involved in mineralization of bone by cleaving phosphate from organic phosphate, was incorporated into GG hydrogels to induce mineralization with calcium phosphate (CaP). Incorporated ALP induced formation of apatite-like material on the submicron scale within GG gels, as shown by FTIR, SEM, EDS, XRD, ICP-OES, TGA and von Kossa staining. Increasing ALP concentration increased amounts of CaP as well as stiffness. Mineralized GG was able to withstand sterilization by autoclaving, although stiffness decreased. In addition, mineralizability and stiffness of GG was enhanced by the incorporation of polydopamine (PDA). Furthermore, mineralization of GG led to enhanced attachment and vitality of cells in vitro while cytocompatibility of the mineralized gels was comparable to one of the most commonly used bone substitute materials. The results proved that ALP-mediated enzymatic mineraliza-tion of GG could be enhanced by functionalization with PDA.

Thermosensitive injectable hydrogels based on chitosan neutralized with sodium beta-glycerophosph... more Thermosensitive injectable hydrogels based on chitosan neutralized with sodium beta-glycerophosphate (Na-β-GP) have been studied as biomaterials for drug delivery and tissue regeneration. Magnesium (Mg) has been reported to stimulate adhesion and proliferation of bone forming cells. With the aim of improving the suitability of the aforementioned chitosan hydrogels as materials for bone regeneration, Mg was incorporated by partial substitution of Na-β-GP with magnesium glycerophosphate (Mg-GP). Chitosan/Na-β-GP and chitosan/Na-β-GP/Mg-GP hydrogels were also loaded with the enzyme alkaline phosphatase (ALP) which induces hydrogel mineralization. Hydrogels were characterized physicochemically with respect to mineralizability and gelation kinetics, and biologically with respect to cytocompatibility and cell adhesion. Substitution of Na-β-GP with Mg-GP did not negatively influence mineralizability. Cell biological testing showed that both chitosan/Na-β-GP and chitosan/Na-β-GP/Mg-GP hydrogels were cytocompatible towards MG63 osteoblast-like cells. Hence, chitosan/Na-β-GP/Mg-GP hydrogels can be used as an alternative to chitosan/Na-β-GP hydrogels for bone regeneration applications. However the incorporation of Mg in the hydrogels during hydrogel formation did not bring any appreciable physicochemical or biological benefit.

Novel injectable, self-gelling hydrogel–microparticle composites for bone regeneration consisting... more Novel injectable, self-gelling hydrogel–microparticle composites for bone regeneration consisting of gellan gum and calcium and magnesium carbonate microparticles

Thermosensitive injectable chitosan hydrogels can be formed by neutralization of acidic chitosan ... more Thermosensitive injectable chitosan hydrogels can be formed by neutralization of acidic chitosan solutions with sodium beta-glycerophosphate (Na-β-GP) coupled with increasing temperature to body temperature. Such hydrogels have been considered for applications in bone regeneration. In this study, chitosan hydrogels were enriched with glycerol and the enzyme alkaline phosphatase (ALP) with a view to improving their suitability as materials for bone tissue engineering. Mineral formation was confirmed by infrared spec-troscopy (FTIR) and increases in the mass fraction of the hydrogel not consisting of water. Incorporation of ALP in hydrogels followed by incubation in a solution containing calcium ions and glycerophosphate, a substrate for ALP, led to formation of calcium phosphate within the hydrogel. MG-63 osteoblast-like cells were cultivated in eluates from hydrogels containing ALP and without ALP at different dilutions and directly on the hydrogel samples. Hydrogels containing ALP exhibited superior cytocompatibility to ALP-free hydrogels. These results pave the way for the use of glycerol-and ALP-enriched hydrogels in bone regeneration.

Mineralization of hydrogel biomaterials is considered desirable to improve their suitability as m... more Mineralization of hydrogel biomaterials is considered desirable to improve their suitability as materials for bone regeneration. Calcium carbonate (CaCO 3) has been successfully applied as a bone regeneration material, but hydrogel-CaCO 3 composites have received less attention. Magnesium (Mg) has been used as a component of calcium phosphate biomaterials to stimulate bone-forming cell adhesion and proliferation and bone regeneration in vivo, but its effect as a component of carbonate-based biomaterials remains uninvestigated. In the present study, gellan gum (GG) hydrogels were mineralized enzymatically with CaCO 3 , Mg-enriched CaCO 3 and magnesium carbonate to generate composite biomaterials for bone regeneration. Hydrogels loaded with the enzyme urease were mineralized by incubation in mineralization media containing urea and different ratios of calcium and magnesium ions. Increasing the magnesium concentration decreased mineral crystallinity. At low magnesium concentrations calcite was formed, while at higher concentrations magnesian calcite was formed. Hydromagnesite (Mg 5 (CO 3) 4 (OH) 2 .4H 2 O) formed at high magnesium concentration in the absence of calcium. The amount of mineral formed and compressive strength decreased with increasing magnesium concentration in the mineralization medium. The calcium: magnesium elemental ratio in the mineral formed was higher than in the respective mineralization media. Mineralization of hydrogels with calcite or magnesian calcite promoted adhesion and growth of osteoblast-like cells. Hydrogels mineralized with hydromagnesite displayed higher cytotoxicity. In conclusion, enzymatic mineralization of GG hydrogels with CaCO 3 in the form of calcite successfully reinforced hydrogels and promoted osteoblast-like cell adhesion and growth, but magnesium enrichment had no definitive positive effect.

Hydrogels are popular materials for tissue regeneration. Incorporation of biologically active sub... more Hydrogels are popular materials for tissue regeneration. Incorporation of biologically active substances, e.g. enzymes, is straightforward. Hydrogel mineralization is desirable for bone regeneration. Here, hydro-gels of Gellan Gum (GG), a biocompatible polysaccharide, were mineralized biomimetically with CaCO 3 using a double enzymatic approach. The enzymes urease (U) and carbonic anhydrase (CA) were incorporated in GG hydrogels. Hydrogels were incubated in a mineralization solution containing U substrate (urea) and calcium ions. U converts urea to ammonia (which raises pH) and CO 2. CA catalyses the reaction of CO 2 with water to form HCO 3 À , which undergoes deprotonation to form CO 3 2À , which react with Ca 2+ to form insoluble CaCO 3. All hydrogels containing U+CA were mineralized more with calcite and stiffer than hydrogels containing U. Mineralization with calcite promoted proliferation and spreading of osteoblast-like cells.

Injectable self-gelling composites for bone tissue engineering based on gellan gum hydrogel enric... more Injectable self-gelling composites for bone tissue engineering based on gellan gum hydrogel enriched with different bioglasses Timothy E L Douglas, Wojciech Piwowarczyk, Elzbieta Pamula et al. Novel injectable, self-gelling hydrogel-microparticle composites for bone regeneration consisting of gellan gum and calcium and magnesium carbonate microparticles Timothy E L Douglas, Agata apa, Katarzyna Reczyska et al. Towards antimicrobial yet bioactive Cu-alginate hydrogels I Madzovska-Malagurski, M Vukasinovic-Sekulic, D Kostic et al. High performance bio-based hyperbranched polyurethane/carbon dot-silver nanocomposite: a rapid self-expandable stent Rituparna Duarah, Yogendra P Singh, Prerak Gupta et al. Injectable osteogenic and angiogenic nanocomposite hydrogels for irregular bone defects M Vishnu Priya, A Sivshanmugam, A R Boccaccini et al.

Coating biomedical implant surfaces with biopolymers is an easy and inexpensive way to impart fun... more Coating biomedical implant surfaces with biopolymers is an easy and inexpensive way to impart func-tionalities. Numerous biocompatible biopolymers, including cationic crustacean-derived chitosans, have been used. Here, substrates of Titanium (Ti), commonly used for bone contact applications, were coated with chitosan and one of three polyphenol-rich plant extracts (PPrPE) and characterized physicochemi-cally. Hela cell adhesion and growth of methicillin-resistant Staphylococcus aureus (MRSA) were studied. Chitosan and PPrPE on surfaces were detected by FTIR and XPS. Chitosan coatings, both with and without PPrPE functionalization, did not inhibit MRSA growth and promoted Hela cell adhesion. The effect of PPrPE functionalization remained unclear.

Biochemistry Research International, 2012

Acta of bioengineering and biomechanics / Wrocław University of Technology, 2016

Thermosensitive injectable chitosan hydrogels can be formed by neutralization of acidic chitosan ... more Thermosensitive injectable chitosan hydrogels can be formed by neutralization of acidic chitosan solutions with sodium betaglycerophosphate (Na-β-GP) coupled with increasing temperature to body temperature. Such hydrogels have been considered for applications in bone regeneration. In this study, chitosan hydrogels were enriched with glycerol and the enzyme alkaline phosphatase (ALP) with a view to improving their suitability as materials for bone tissue engineering. Mineral formation was confirmed by infrared spectroscopy (FTIR) and increases in the mass fraction of the hydrogel not consisting of water. Incorporation of ALP in hydrogels followed by incubation in a solution containing calcium ions and glycerophosphate, a substrate for ALP, led to formation of calcium phosphate within the hydrogel. MG-63 osteoblast-like cells were cultivated in eluates from hydrogels containing ALP and without ALP at different dilutions and directly on the hydrogel samples. Hydrogels containing ALP ex...

Biomedical materials (Bristol, England), 2016

Hydrogels offer several advantages as biomaterials for bone regeneration, including ease of incor... more Hydrogels offer several advantages as biomaterials for bone regeneration, including ease of incorporation of soluble substances such as mineralization-promoting enzymes and antibacterial agents. Mineralization with calcium phosphate (CaP) increases bioactivity, while antibacterial activity reduces the risk of infection. Here, gellan gum (GG) hydrogels were enriched with alkaline phosphatase (ALP) and/or Seanol(®), a seaweed extract rich in phlorotannins (brown algae-derived polyphenols), to induce mineralization with CaP and increase antibacterial activity, respectively. The sample groups were unmineralized hydrogels, denoted as GG, GG/ALP, GG/Seanol and GG/Seanol/ALP, and hydrogels incubated in mineralization medium (0.1 M calcium glycerophosphate), denoted as GG/ALP_min, GG/Seanol_min and GG/Seanol/ALP_min. Seanol(®) enhanced mineralization with CaP and also increased compressive modulus. Seanol(®) and ALP interacted in a non-covalent manner. Release of Seanol(®) occurred in a bur...

Materials Letters, Oct 28, 2015

In the current study, the effect of post-plasma grafting of 2-aminoethyl methacrylate (AEMA) and ... more In the current study, the effect of post-plasma grafting of 2-aminoethyl methacrylate (AEMA) and the subsequent covalent immobilization of gelatin (GelB) on poly(L-lactide-co-glycolide) (PLGA) thin films were investigated. The applied modification resulted in surface chemistry changes of PLGA. More specifically, an increase of nitrogen from 0 at% to 14 at% with a concomitant decrease in carbon and oxygen concentration was observed. The samples were more hydrophilic after the treatment as reflected by a decrease of the water contact angle from 721 to 331 and more rough at the nanoscale as shown by atomic force microscopy (increase of R a roughness from 0.7 nm to 10 nm). The growth of osteoblast-like MG-63 cells was enhanced on biofunctionalised PLGA-AEMA-GelB surfaces and the cells were more homogenously distributed than on non-modified PLGA. Our findings are especially important for tissue engineering applications, where substrates supporting homogenous cell cultures are particularly promising.

The International Journal of Oral Maxillofacial Implants, 2011

Purpose: Human mesenchymal stem cells (hMSCs) hold the potential for bone regeneration because of... more Purpose: Human mesenchymal stem cells (hMSCs) hold the potential for bone regeneration because of their self-renewing and multipotent character. The goal of this study was to evaluate the influence of collagen membranes on the proliferation of hMSCs derived from bone marrow. A special focus was set on short-term eluates derived from collagen membranes, as volatile toxic materials washed out from these membranes may influence cell behavior during the short time course of oral surgery. Materials and Methods: The proliferation of hMSCs seeded directly on a collagen membrane (BioGide) was evaluated quantitatively using the cell proliferation reagent were performed using hMSCs cultivated in eluates from membranes incubated for 10 minutes, 1 hour, or 24 hours in serum-free cell culture medium. The data were analyzed statistically. Results: Scanning electron microscopy showed large numbers of hMSCs with well-spread morphology on the collagen membranes after 7 days of culture. The WST test revealed significantly better proliferation of hMSCs on collagen membranes after 4 days of culture compared to cells cultured on a cover glass. Cytotoxicity levels were low, peaking in short-term eluates and decreasing with longer incubation times. Conclusion: Porcine collagen membranes showed good biocompatibility in vitro for hMSCs. If maximum cell proliferation rates are required, a prewash of membranes prior to application may be useful. Int J Oral MaxIllOfac IMplants 2011;26:1004-1010

Journal of biomedical materials research. Part A, Jan 7, 2016

Enrichment of hydrogels with inorganic particles improves their suitability for bone regeneration... more Enrichment of hydrogels with inorganic particles improves their suitability for bone regeneration by enhancing their mechanical properties, mineralizability and bioactivity as well as adhesion, proliferation and differentiation of bone-forming cells, while maintaining injectability. Low aggregation and homogeneous distribution maximize particle surface area, promoting mineralization, cell-particle interactions and homogenous tissue regeneration. Hence, determination of the size and distribution of particles/particle agglomerates in the hydrogel is desirable. Commonly used techniques have drawbacks. High-resolution techniques (e.g. SEM) require drying. Distribution in the dry state is not representative of the wet state. Techniques in the wet state (histology, µCT) are of lower resolution. Here, self-gelling, injectable composites of Gellan Gum (GG) hydrogel and two different types of sol-gel derived bioactive glass (bioglass) particles were analyzed in the wet state using Synchrotro...

Journal of Tissue Engineering and Regenerative Medicine, 2015

Gellan gum hydrogels functionalized with alkaline phosphatase were enzymatically mineralized with... more Gellan gum hydrogels functionalized with alkaline phosphatase were enzymatically mineralized with phosphates in mineralization medium containing calcium (Ca) and zinc (Zn) to improve their suitability as biomaterials for bone regeneration. The aims of the study were to endow mineralized hydrogels with antibacterial activity by incorporation of Zn in the inorganic phase, and to investigate the effect of Zn incorporation on the amount and type of mineral formed, the compressive modulus of the mineralized hydrogels and on their ability to support adhesion and growth of MC3T3-E1 osteoblast-like cells. Mineralization medium contained glycerophosphate (0.05 m) and three different molar Ca:Zn ratios, 0.05:0, 0.04:0.01 and 0.025:0.025 (all mol/dm(3) ), hereafter referred to as A, B and C, respectively. FTIR, SAED and TEM analysis revealed that incubation for 14 days caused the formation of predominantly amorphous mineral phases in sample groups A, B and C. The presence of Zn in sample groups B and C was associated with a drop in the amount of mineral formed and a smaller mineral deposit morphology, as observed by SEM. ICP-OES revealed that Zn was preferentially incorporated into mineral compared to Ca. Mechanical testing revealed a decrease in compressive modulus in sample group C. Sample groups B and C, but not A, showed antibacterial activity against biofilm-forming, methicillin-resistant Staphylococcus aureus. All sample groups supported cell growth. Zn incorporation increased the viable cell number. The highest values were seen on sample group C. In conclusion, the sample group containing the most Zn, i.e. group C, appears to be the most promising. Copyright © 2015 John Wiley & Sons, Ltd.

Carbohydrate Polymers, 2015

Injectable hydrogels for bone regeneration consisting of chitosan, sodium beta-glycerophosphate (... more Injectable hydrogels for bone regeneration consisting of chitosan, sodium beta-glycerophosphate (Na-␤-GP) and alkaline phosphatase (ALP) were enriched with the polyphenols phloroglucinol (PG) and gallic acid (GA) and characterized physicochemically and biologically with respect to properties relevant for applications in bone regeneration, namely gelation kinetics, mineralizability, antioxidant properties, antibacterial activity, cytocompatibility and ability to support adhesion and growth of human osteoblast-like MG63 cells. Enrichment with PG and GA had no negative effect on gelation kinetics and mineralizability. PG and GA both enhanced antioxidant activity of unmineralized hydrogels. Mineralization reduced antioxidant activity of hydrogels containing GA. Hydrogels containing GA, PG and without polyphenols reduced colony forming ability of Escherichia coli after 1 h, 3 h and 6 h incubation and slowed E. coli growth in liquid culture for 150 min. Hydrogels containing GA were cytotoxic and supported cell growth more poorly than polyphenol-free hydrogels. PG had no negative effect on cell adhesion and growth.

The International journal of oral & maxillofacial implants

Human mesenchymal stem cells (hMSCs) hold the potential for bone regeneration because of their se... more Human mesenchymal stem cells (hMSCs) hold the potential for bone regeneration because of their self-renewing and multipotent character. The goal of this study was to evaluate the influence of collagen membranes on the proliferation of hMSCs derived from bone marrow. A special focus was set on short-term eluates derived from collagen membranes, as volatile toxic materials washed out from these membranes may influence cell behavior during the short time course of oral surgery. The proliferation of hMSCs seeded directly on a collagen membrane (BioGide) was evaluated quantitatively using the cell proliferation reagent WST-1 (4-3-[4-iodophenyl]-2-[4-nitrophenyl]-2H-[5-tetrazolio]-1, 3--benzol-disulfonate) and qualitatively by scanning electron microscopy. Two standard biocompatibility tests, namely the lactate dehydrogenase and MTT (3-[4, 5-dimethyl-2-thiazolyl]-2, 5-diphenyl-2H-tetrazoliumbromide) tests, were performed using hMSCs cultivated in eluates from membranes incubated for 10 mi...