3D-Printed Oxygen-Carrying Nanocomposite Hydrogels for Enhanced Cell Viability under Hypoxic and Normoxic Conditions.

Insufficient and heterogeneous oxygen (O2) distribution within engineered tissues results in hypoxic conditions. Hypoxia is one of the characteristics of solid tumors. To date, very few studies have used an O2-deliverable injectable hydrogel for cancer treatment under hypoxic conditions. In this field, we describe a new O2-carrying nanomaterial and an injectable nanocomposite hydrogel (PMOF and AlgL-PMOF, respectively) that can provide extended oxygen levels for cell survival under hypoxia. Particularly, PMOF and AlgL-PMOF enhance cell viability under hypoxic and normoxic cell culturing conditions. Moreover, sustained oxygen availability in the presence of an anticancer drug within the 3D network of AlgL-PMOF results in a decrease in the viability of malignant and immortal cells, while the viability of healthy cells increases.

Functional Nanomaterials and 3D-Printable Nanocomposite Hydrogels for Enhanced Cell Proliferation and for the Reduction of Bacterial Biofilm Formation.

Biomaterial-associated infections are a major cause of biomaterial implant failure. To prevent the initial attachment of bacteria to the implant surface, researchers have investigated various surface modification methods. However, most of these approaches also prevent the attachment, spread, and growth of mammalian cells, resulting in tissue integration failure. Therefore, the success of biomaterial implants requires an optimal balance between tissue integration (cell adhesion to biomaterial implants) and inhibition of bacterial colonization. In this regard, we synthesize bifunctional nanomaterials by functionalizing the pores and outer surfaces of periodic mesoporous organosilica (PMO) with antibacterial tetracycline (Tet) and antibacterial and cell-adhesive bipolymer poly-d-lysine (PDL), respectively. Then, the fabricated TetPMO-PDL nanomaterials are incorporated into alginate-based hydrogels to create injectable and 3D-printable nanocomposite (NC) hydrogels (AlgL-TetPMO-PDL). These bifunctional nanomaterial and 3D-printable NC hydrogel show pH-dependent release of Tet over 7 days. They also enhance the proliferation of eukaryotic cells (fibroblasts). TetPMO-PDL is inactive in reducing Pseudomonas aeruginosa, Staphylococcus aureus, and Enterococcus faecalis biofilms. However, AlgL-TetPMO-PDL shows significant antibiofilm activity against P. aeruginosa. These results suggest that the incorporation of TetPMO-PDL into AlgL may have a synergistic effect on the inhibition of the Gram-negative bacterial (P. aeruginosa) biofilm, while this has no effect on the reduction of the Gram-positive bacterial (S. aureus and E. faecalis) biofilm.

Bifunctional nanomaterials for simultaneously improving cell adhesion and affecting bacterial biofilm formation on silicon-based surfaces.

In the biomedical field, silicon-based materials are widely used as implants, biomedical devices, and drug delivery systems. Although these materials show promise for implant technologies and clinical applications, many of them fail to simultaneously possess key properties, such as mechanical stability, biostability, stretchability, cell adhesiveness, biofilm inhibition, and drug delivery ability. Therefore, there is considerable need for the development and improvement of new biomaterials with improved properties. In this context, we describe the synthesis of a new hybrid nanocomposite material that is prepared by incorporating bifunctional nanomaterials onto glass and polydimethylsiloxane surfaces. The results show that our hybrid nanocomposite material is elastic, stretchable, injectable, biostable, has pH-controlled drug delivery ability, and display improved cell adhesion and proliferation and, at the same time, impacted bacterial biofilm formation on the respective surfaces.

Directed vertical cell migration via bifunctionalized nanomaterials in 3D step-gradient nanocomposite hydrogels.

Directional cell migration plays an important role in embryonic development, tissue regeneration, wound healing, and proper immune responses. In order to control cell migration, various gradient biomaterials have been fabricated. Although most of these systems have been designed to study cell migration in the horizontal (XY) plane, the migration of cells in the vertical plane (bottom to top: XZ) is crucial for wound healing, development of the cerebellum, and metastatic processes. In this study, we designed new step-gradient nanocomposite (NC) scaffolds by 3D printing different layers of NC hydrogels containing increasing concentrations of bifunctional nanomaterials (NMs). The synthesized bifunctional NMs are stimuli (pH) responsive and, when integrated into the 3D network of the step-gradient NC scaffolds, provide sustained release of bioactive molecules, which is beneficial for local drug delivery applications. We demonstrate that bifunctional NMs used in vertically increasing concentrations can influence the migration of cells in the XZ plane of the step-gradient NC scaffolds. Further, the bifunctional NMs improve the viability of healthy cells and promote their migration in the XZ plane of the step-gradient NC scaffolds, they simultaneously inhibit the concurrent migration and growth of cancer cells due to the pH-responsive release of bioactive molecules.

Injectable oxygen-generating nanocomposite hydrogels with prolonged oxygen delivery for enhanced cell proliferation under hypoxic and normoxic conditions.

We describe a new organic peroxide-based injectable biomaterial that was prepared by using benzoylperoxide and LAPONITE® incorporated into an alginate hydrogel (BPO-AlgL). BPO-AlgL shows sustained release of O2 over a period of 14 days and reduces the hypoxia-induced cell death. BPO-AlgL also promotes enhanced cell viability by providing sustained O2 within the 3D AlgL scaffold. In addition, BPO-AlgL increases the O2 level in the environment of the cells, which led to a decrease in the proliferation of malignant cells, while it also resulted in an increase in the viability of healthy fibroblast cells. Therefore, our new oxygen generating organic peroxide-based injectable 3D biomaterials have potential to contribute in the development of next generation advanced tissue engineering biomaterials.

Injectable polymer/nanomaterial composites for the fabrication of three-dimensional biomaterial scaffolds.

Current tissue engineering techniques have been intensively focused on creating injectable systems that can be used in minimally invasive surgery and controlled local drug delivery applications. The materials developed so far are based on natural and synthetic polymers and their nanocomposites, but many of them fail to simultaneously provide mechanical stability, stretchability and enhanced cell adhesiveness. In this context, to generate advanced injectable nanocomposite polymers that concurrently possess several properties, we used nanomaterials as well as nanomaterials that are chemically functionalized with bioactive molecules. Our 3D-printed polymer/nanomaterial composites (nanocomposite polymers) displayed enhanced mechanical properties, good shape fidelity, non-toxicity, stretchability, biostability and cell adhesiveness.

3D printing of step-gradient nanocomposite hydrogels for controlled cell migration.

In this study, we report the step-gradient nanocomposite (NC) hydrogel generated easily by spatial connection of different nanocomposite hydrogel pastes varying in the concentrations of nanomaterials with the aid of a 3D printing technique. The prepared 3D printed gradient NC hydrogel has self-adhesive properties and is used to direct the migration of fibroblast cells towards the higher concentration of biopolymer-coated silica-based nanomaterials (NMs) within the 3D network of the hydrogel. Furthermore, we demonstrate the potential application of our gradient NC hydrogel in migration and subsequent enhanced osteogenic differentiation of human bone marrow derived mesenchymal stem cells (hBM MSC). The osteogenic differentiation of hBM MSC is achieved in the absence of osteogenic differentiation medium due to the silica-based NMs. The increase in the NM content in the gradient construct promotes hBM MSC migration and results in higher Ca2+ deposition.

3D bioprinting of triphasic nanocomposite hydrogels and scaffolds for cell adhesion and migration.

In this study we describe the first example of 3D bioprinted triphasic chiral nanocomposite (NC) hydrogels/scaffolds to simulate the complex 3D architecture, nano/micro scale topography, and chiral nature of extracellular matrix. These multifunctional constructs are prepared using a 3D bioprinting technique and are composed of three connected hydrogels/scaffolds, two of which are loaded with nanomaterials functionalized with opposite enantiomers of a biomolecule. With these constructs, we direct the migration of cells toward the part of the triphasic chiral NC hydrogels/scaffolds containing the cells' preferred biomolecule enantiomer.

Self-assembled monolayers of chiral periodic mesoporous organosilica as a stimuli responsive local drug delivery system.

We present the preparation of self-assembled monolayers (SAMs) of pH responsive chiral periodic mesoporous organosilicas (PMOs) as model implants with drug delivery ability. SAMs of pH responsive PMOs were prepared by layer-by-layer coating of PMOs with polyelectrolytes (e.g. the enantiomers of a polycation biopolymer), for delivering organic molecules and anticancer drug molecules locally in a controlled manner to the adhered cells. We demonstrate that the amount of primary fibroblast, immortal NIH 3T3, and malignant Colo 818 cells adhered to the SAM of the d-enantiomer of polycation-functionalized PMOs was higher in comparison to that of the l-enantiomer of the polycation-functionalized PMO monolayer. In addition, we observe that the 3T3 and Colo cells internalized more of the organic and anticancer drug molecules (released from pH responsive PMOs) than the primary cells did due to the local acidic environment of them. Therefore, as the chirality of the PMOs influenced the amount of cells that adhered, the released molecules interacted with different amounts of cells which allowed us to tune the extent of local drug delivery.

Chirality-dependent cell adhesion and enrichment in Janus nanocomposite hydrogels.

To assess chirality-dependent cell adhesion and cell enrichment in an extracellular matrix (ECM)-like model, in this study we created 3D nanocomposite (NC) hydrogels composed of periodic mesoporous organosilica (PMO) functionalized with chiral molecules [NC "homo-hydrogels" (NC hydrogels with one kind of functionalized PMO)]. Additionally, we prepared Janus NC hydrogel by connecting two enantiomorphous NC hydrogels, producing an advanced material that can be used to investigate the effect of opposite enantiomers on the behaviors of healthy and cancer cells in a single biomaterial at the same time and under the same reaction conditions. We found that the surface chirality of the functionalized PMO particles strongly influenced cell affinity to the NC hydrogels, especially in serum-containing media. Additionally, chirality was also successfully used to enrich healthy cells within the Janus NC hydrogel from a mixture of healthy cells and cancer cells.

Janus Nanocomposite Hydrogels for Chirality-Dependent Cell Adhesion and Migration.

Recently, there has been much interest in the chirality-dependent cell affinity to enantiomorphous nanomaterials (NMs), since, at the nanoscale level, enantiomers of (bio)molecules have different effects on cell behaviors. In this respect, this study used enantiomorphous NMs with which to generate the Janus nanocomposite (NC) hydrogels as multifunctional biomaterials for studying chirality-dependent cell adhesion and cell migration. These Janus NC hydrogels possess two enantiomorphous NC hydrogels, in which the different halves of the hydrogel contain the opposite enantiomers of a biopolymer functionalized nanomaterials. Thus, the enantiomers contact each other only at the midline of the hydrogel but are otherwise separated, yet they are present in the same system. This advanced system allows us to simultaneously study the impact that each enantiomer of a biopolymer has on cell behavior under the same reaction conditions, at the same time, and using only a single biomaterial. Our results show that cells have higher affinity for and migrate toward the part of the Janus NC hydrogel containing the biopolymer enantiomer that the cells prefer.

Nanocomposite Hydrogels and Their Applications in Tissue Engineering.

Nanocomposite (NC) hydrogels, organic-inorganic hybrid materials, are of great interest as artificial three-dimensional (3D) biomaterials for biomedical applications. NC hydrogels are prepared in water by chemically or physically cross-linking organic polymers with nanomaterials (NMs). The incorporation of hard inorganic NMs into the soft organic polymer matrix enhances the physical, chemical, and biological properties of NC hydrogels. Therefore, NC hydrogels are excellent candidates for artificial 3D biomaterials, particularly in tissue engineering applications, where they can mimic the chemical, mechanical, electrical, and biological properties of native tissues. A wide range of functional NMs and synthetic or natural organic polymers have been used to design new NC hydrogels with novel properties and tailored functionalities for biomedical uses. Each of these approaches can improve the development of NC hydrogels and, thus, provide advanced 3D biomaterials for biomedical applications.

Cell Growth on ("Janus") Density Gradients of Bifunctional Zeolite L Crystals.

Nanoparticle density gradients on surfaces have attracted interest as two-dimensional material surfaces that can mimic the complex nano-/microstructure of the native extracellular matrix, including its chemical and physical gradients, and can therefore be used to systematically study cell-material interactions. In this respect, we report the preparation of density gradients made of bifunctional zeolite L crystals on glass surfaces and the effects of the density gradient and biopolymer functionalization of zeolite L crystals on cell adhesion. We also describe how we created "Janus" density gradient surfaces by gradually depositing two different types of zeolite L crystals that were functionalized and loaded with different chemical groups and guest molecules onto the two distinct sides of the same glass substrate. Our results show that more cells adhered on the density gradient of biopolymer-coated zeolites than on uncoated ones. The number of adhered cells increased up to a certain surface coverage of the glass by the zeolite L crystals, but then it decreased beyond the zeolite density at which a higher surface coverage decreased fibroblast cell adhesion and spreading. Additionally, cell experiments showed that cells gradually internalized the guest-molecule-loaded zeolite L crystals from the underlying density gradient containing bifunctional zeolite L crystals.