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Results for “Biomimetics”

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At least 55 records · Page 3Linked to original sources

PubMed1997

Six month clinical evaluation of a biomimetic hydrogel contact lens.

PURPOSE: We performed a six-month, comparative, contralateral/bilateral study to assess the clinical performance of the Proclear contact lens, which is manufactured from a novel, biomimetic, 59% water content, hydrogel material (Omafilcon A). Omafilcon A is a hydrogel polymer and is based on a new biomimetic approach to the design of biomaterials for biomedical applications. The polymer incorporates a synthetic analogue of the phosphorylcholine (PC) headgroup, an important component found in all human cells. METHODS: Forty-two subjects were fit with the Proclear lens for 6 months of daily wear; 20 subjects wore a Proclear lens in one eye and a Permaflex lens in the fellow as a control, while 22 subjects wore Proclear lenses in both eyes. A one-step hydrogen peroxide system was used for disinfection and no protein remover was used. RESULTS: No subject was required to withdraw due to unacceptable physiological findings with the Proclear lens. At the 3-month visit, corneal staining was present in 33% of the Proclear eyes compared to 72% of the Permaflex-wearing eyes. At one month, the Proclear lens was graded significantly more comfortable than the Permaflex lens (P < 0.01), and all 11 of the subjects who expressed a preference did so in favor of the Proclear lens. Overall, the fitting characteristics and visual performance of the Proclear lens did not appear to vary during the study. Spectrofluorimetric analysis of worn lenses confirm that Proclear showed minimal protein and lipid spoliation, which was found to be independent of wear time and subject variations. In contrast, despite the use of a surfactant cleaner, Permaflex lenses showed measurable and significant levels of lipid spoilation. Despite significant differences in average mean thicknesses and the level of bulk water in the lenses, in vivo dehydration of the Proclear lens was significantly lower than that of the Permaflex lens. CONCLUSIONS: The results of this study have confirmed the viability of biomimetic PC-hydrogels in contact lens applications. In vivo and in vitro analyses tended to confirm that Omafilcon A has a number of superior material attributes, as compared to conventional hydrogels when used in contact lens applications.

Adolescent↗

PubMed2006

Biomimetic artificial ECMs stimulate bone regeneration.

We demonstrate that a biomimetic polymer network is capable of affecting bone regeneration in vivo. Starting with a foundation consisting of an environmentally responsive poly(N-isopropylacrylamide-co-acrylic acid) hydrogel, we incorporated matrix metalloproteinase-13 (MMP-13) degradable crosslinkers and peptides containing integrin-binding domains (i.e., Arg-Gly-Asp) to create a biomimetic matrix designed to encourage osteoblast migration and proliferation. We independently tuned matrix stiffness and peptide concentration to generate a response surface model of osteoblast proliferation on different types of matrices. Osteoblast proliferation was significantly influenced by matrix stiffness (i.e., its complex modulus) and peptide concentration. When implanted in a rat femoral ablation model, these matrices induced bone regeneration only when protease degradable crosslinks were used to create the network. For the matrices with MMP-13 degradable crosslinkers, the bone formed had a trabecular-like structure and was distributed throughout the marrow space. Based on the correlated effects of matrix stiffness and ligand concentration, the response surface model will facilitate improvements in the regenerative capacity of these artificial extracellular matrices.

Animals↗

PubMed2001

Rapid fabrication of three-dimensional porous films with biomimetic patterns by natural evaporation of amphiphilic polyacetylene solutions under ambient conditions.

A simple process for fast fabrication of thin films with biomimetic morphological structures from a group of linear homopolymers is developed. Natural evaporation of tetrahydrofuran, chloroform, and hexane-dichloromethane solutions of poly(phenylacetylene)s that contain amino acid and ethylene glycol moieties under ambient conditions instantly produces three-dimensional porous films with structural patterns reminiscent of honeycombs and radiolarian shells. Morphological analysis by optical and electronic microscopy suggests that vesicles of the amphiphilic polymers serve as building blocks in the self-organization to the biomimetic structures.

Acetylene↗

PubMed2003

Biological performance of biomimetic calcium phosphate coating of titanium implants in the dog mandible.

The aim of the present study was to analyze the in vivo effect of biomimetic calcium phosphate coating of titanium implants on periimplant bone formation and bone-/implant contact. Five types of implants were used: 1) Ti6Al4V implants with a polished surface; 2) Ti6Al4V implants with collagen coating; 3) Ti6Al4V implants with a mineralized collagen layer; 4) Ti6Al4V implants with sequential coating of hydroxyapatite (HA) and collagen; and 5) Ti6Al4V implants with HA coating only. All implants had square cross sections with an oblique diameter of 4.6 mm and were inserted press fit into trephine burr holes of 4.6 mm in the mandibles of ten beagle dogs. The implants of five animals each were evaluated after a healing period of 1 month and 3 months, respectively, during which time sequential fluorochrome labeling of bone formation had been performed. Bone formation was evaluated by morphometric measurement of the newly formed bone around the implants and the percentage of implant bone contact. After 1 month, there was a significantly higher percentage of mean bone/implant contact in the HA-coated implants compared to those with polished surface and those with the collagen-coated surface. After 3 months, these differences were not present anymore. Bone apposition was significantly higher next to implants with sequential HA/collagen coating compared to polished surfaces and mineralized collagen layer. It is concluded that biomimetic coating of titanium implants with HA has shown the clearest trend to increase bone-implant contact in the early ingrowth period. The addition of collagen to an HA coating layer may hold some promise when used as sequential HA/collagen coating with mineralized collagen as the surface layer.

Alloys↗

PubMed2004

In vivo evaluation of a biomimetic apatite coating grown on titanium surfaces.

Osteoconductive mineral coatings represent an established technology for enhancing the integration of orthopedic implants with living bone. However, current coatings have limitations related to fabrication methods, attachment strength to metal substrates, and in vivo performance. Low temperature biomimetic growth is a coating technique wherein the device to be coated is immersed in a meta-stable saturated solution of the coating constituents and growth of the coating is then allowed to proceed on the surface of the device. This study focused on the in vivo evaluation of a biomimetic apatite coating fabricated under these conditions. The experiment was designed to specifically test the amount of bone ingrowth into the coated channels versus the uncoated channels of an established bone chamber system, with emphasis placed on the amount of bone present on the coupon surface. Three types of measurements were taken on each channel: linear ingrowth %, area ingrowth %, and continuous bone apposition %. The experiments demonstrated that under controlled conditions, the apatite coating appears to resorb in 8 weeks and did stimulate early osseointegration with the metal surface with a reduction in fibrous tissue encapsulation. This coating may, therefore, be useful in facilitating early bone ingrowth into porous surfaces without the potential for coating debris, macrophage infiltration, fibrous tissue encapsulation, and eventual coating failure as may occur with current plasma-sprayed hydroxapatite coating techniques.

Animals↗

PubMed2005

Microscale multilayer cocultures for biomimetic blood vessels.

Living tissues have complex and well-organized microstructures. Although microtechnology has been used to create in vivo-like cell microstructures in vitro, most available microscale systems are two-dimensional, and few three-dimensional (3D) systems have been explored. This article demonstrates a 3D hierarchical biomimetic multilayer microsystem created by a generally applicable technique. The technique employs layer-by-layer microfluidics to build layers of cells and biopolymers in microchannels, allowing controlled patterning of cells and their microenvironments in the x, y, and z-dimension. As a prototype, a multilayer system was created using three vascular cell types within heterogeneous types of biopolymers to mimic the structure and composition of a blood vessel wall. The effects of matrix composition and multilayer configurations on 3D cell-cell interactions and cell biology were revealed. Cell migration in the z-dimension, matrix remodeling, intercellular adhesion molecule expression and actin organization were examined under different 3D coculture conditions. A more biomimetic coculture was found to reproduce a more stable structure and in vivo-like function. This approach provides a method to fabricate microscale hierarchical "neotissues" with 3D configurations of matrix materials and multiple cell types, and an in vitro cell coculture model to understand 3D processes of cell-cell and cell-matrix interactions.

Actin Cytoskeleton↗

PubMed2005

Biomimetic porous scaffolds with high elasticity made from mineralized collagen--an animal study.

Histological investigations of a new hydroxyapatite-collagen composite material were carried out to evaluate its possible suitability as a bone substitute. The three-dimensional scaffolds made from biomimetically mineralized collagen exhibit an interconnecting pore structure and elastic mechanical properties. They were implanted into the subcutaneous tissue and bone defects made in the femur of rats and harvested with the surrounding tissue at 1, 2, 4, 8, and 12 weeks after surgery. The materials implanted in the subcutaneous tissue were covered by fibrous connective tissue with a slight inflammatory response, and many foreign-body giant cells were observed on the surface of the scaffolds. Most of the material implanted in the subcutaneous tissue was resorbed at 8 weeks by phagocytosis. In the bone defects, new bone formation was observed on the surface of the material at 1 week. New bone increased with time, and osteoclasts were seen on the surface of the scaffolds at 2 weeks. Resorption and replacement by new bone of many parts of the materials implanted in the femur were observed by 12 weeks. These responses occurred faster than those of other hydroxyapatite-collagen composites. The results suggested that the new biomimetically mineralized collagen scaffolds were suitable as an implant material for bone-tissue reconstruction.

Animals↗

PubMed2005

Novel biomimetic surfactant: synthesis and micellar characteristics.

Novel biomimetic surfactants based on cholesterol as the hydrophobic segment and poly[2-(methacryloyloxy)ethyl phosphorylcholine] (pMPC) as the hydrophilic segment were synthesized in the present study by atom transfer radical polymerization (ATRP) of 2-(methacryloyloxy)ethyl phosphorylcholine (MPC) using a cholesterol-based macroinitiator. The association behavior of cholesterol-block-poly[2-(methacryloyloxy)ethyl phosphorylcholine] (Chol-pMPCs) in aqueous solution was studied by (1)H NMR spectroscopy, fluorescence probe technique, and atomic force microscopy (AFM). The (1)H NMR spectrum of the polymer in CD(3)OD showed both the cholesterol group and the phosphorylcholine group while the cholesterol group did not appeared in the (1)H NMR spectrum of the polymer in D(2)O, which implied the formation of a micelle structure. Fluorescence excitation spectra of a pyrene probe solubilized in the aggregates of Chol-pMPCs suggested the presence of a critical micelle concentration (cmc) in water. The critical micelle concentrations of the polymers CMPC10, CMPC20 and CMPC40 were determined to be 7.27 x 10(-3), 13.47 x 10(-3), and 20.77 x 10(-3) mg . mL(-1), respectively. AFM images of the aggregates on mica suggested that the pMPC block formed the biocompatible micelle coronas and the cholesterol block formed the hydrophobic micelle cores. These new biomimetic diblock copolymers were evaluated as "stealthy" nanocapsules for the delivery of hydrophobic drugs. The anti-cancer drug adriamycin (ADR) was chosen as a hydrophobic drug to be incorporated into the inner core of the micelles and the morphology of the drug-loaded micelles were observed by AFM.

Biomimetic Materials↗

PubMed2007

Controlling tissue microenvironments: biomimetics, transport phenomena, and reacting systems.

The reconstruction of tissues ex vivo and production of cells capable of maintaining a stable performance for extended time periods in sufficient quantity for synthetic or therapeutic purposes are primary objectives of tissue engineering. The ability to characterize and manipulate the cellular microenvironment is critical for successful implementation of such cell-based bioengineered systems. As a result, knowledge of fundamental biomimetics, transport phenomena, and reaction engineering concepts is essential to system design and development. Once the requirements of a specific tissue microenvironment are understood, the biomimetic system specifications can be identified and a design implemented. Utilization of novel membrane systems that are engineered to possess unique transport and reactive features is one successful approach presented here. The limited availability of tissue or cells for these systems dictates the need for microscale reactors. A capstone illustration based on cellular therapy for type 1 diabetes mellitus via encapsulation techniques is presented as a representative example of this approach, to stress the importance of integrated systems.

Biological Transport, Active↗

PubMed2005

Biomimetic mineralization of partially bioresorbable glass fiber reinforced composite.

The aim of this study was to investigate the biomimetic mineralization on the surface of a glass fiber reinforced composite with partially resorbable biopolymer matrix. The E-glass fibers were preimpregnated with a novel biopolymer of poly(hydroxyproline) amide, and further impregnated in the monomer system of bis-phenyl glycidyl dimethacrylate (Bis-GMA)--triethylene glycol dimethacrylate (TEGDMA), which formed interpenetrating polymer networks (IPN) with the preimpregnation polymer. After light-initiated polymerization of the monomer system, the rhombic test specimens (n = 6) were immersed in the simulated body fluid (SBF) with the bioactive glass for 24 h, and then the apatite nuclei were allowed to grow for 1, 3, 5 and 7 days in the SBF. The control test specimens (n = 3) were immersed in SBF without the bioactive glass. According to the scanning electron microscope (SEM), a mineral layer was formed on the surface of all the specimens, which were immersed with bioactive glass. The layer was thickened by the prolonged immersion time to a uniform layer. The Ca/P atomic ratio of the mineral varied between 1.30 and 1.54 as analyzed by the energy dispersive X-ray analysis (EDXA). The Fourier transform infrared spectroscopy (FT-IR) spectra gave signals for the mineral, which are characteristic of both bone-like apatite and orthocalciumphosphate. In conclusion, the mineral layer was formed on the surfaces of the specimens by biomimetic mineralization, the mineral being a mixture of bone-like apatite, orthocalciumphosphate and other calcium phosphates.

Apatites↗

PubMed2007

A novel bioactive porous bredigite (Ca7MgSi4O16) scaffold with biomimetic apatite layer for bone tissue engineering.

The aim of this study was to develop a novel bioactive, degradable and cytocompatible bredigite (Ca(7)MgSi(4)O(16)) scaffold with biomimetic apatite layer for bone tissue engineering. Porous bredigite scaffolds were prepared using polymer sponge method. The bredigite scaffolds with biomimetic apatite layer (BTAP) were obtained by soaking bredigite scaffolds in simulated body fluid (SBF) for 10 days. The porosity and in vitro degradability of BTAP scaffolds were investigated. In addition, osteoblast-like cell morphology, proliferation and differentiation on BTAP scaffolds were evaluated and compared with beta-tricalcium phosphate (beta-TCP) scaffolds. The results showed that BTAP scaffolds possessed 90% of porosity. The degradation of BTAP scaffolds was comparable to that of beta-TCP scaffolds. Cells on BTAP scaffolds spread well and presented a higher proliferation rate and differentiation level as compared with those on beta-TCP scaffolds. Our results indicated that BTAP scaffolds were degradable and possessed the function to enhance cell proliferation and differentiation, and might be used as bone tissue engineering materials.

Absorbable Implants↗

PubMed2006

Synthesis and sintering of biomimetic hydroxyapatite nanoparticles for biomedical applications.

Synthesis of monodisperse nanoparticles with uniform morphology and narrow size distribution as achieved by nature is a challenge to materials scientists. Mimicking the process of biomineralization has led to the development of biomolecules mediated synthesis of nanoparticles that overcomes many of the problems associated with nanoparticle synthesis. Termed as biomimetics this paradigm shift in the philosophy of synthesis of materials is very advantageous for the design-based synthesis of nanoparticles. The effect of concentration of a protein named bovine serum albumin on particle size, morphology and degree of crystallinity of biomimetically synthesized hydroxyapatite particles, has been studied. Results establish 0.5% protein as the required concentration to produce 30-40 nm sized hydroxyapatite particles with an optimum degree of crystallinity as required for biomedical applications. These particles synthesized under certain stringent conditions are found to have stoichiometric calcium:phosphorus ratio of 1.67 and exhibit restricted grain growth during sintering.

Biomimetic Materials↗

PubMedDate not supplied

Layer-by-layer microfluidics for biomimetic three-dimensional structures.

Due to the complex structures of living systems, with size scales spanning from the micron to millimeter range, the use of microtechnology to recreate in vivo-like architecture has exciting potential applications. However, most microscale systems are two-dimensional, and few three-dimensional (3-D) systems are being explored. We have developed a versatile technique, combining surface engineering with layer-by-layer microfluidics technology, to create a 3-D microscale hierarchical tissue-like structure. The process involves immobilization of a cell-matrix assembly, cell-matrix contraction, and pressure-driven microfluidic delivery. An aminopropyltriethoxysilane-glutaraldehyde activated chip is used to effectively immobilize the cell-matrix assemblies while maintaining cell viability. Pressure-driven microfluidics is applied to transport cells-matrices with controlled flow rates, determined from dynamic flow imaging. By taking advantage of the contraction of the biopolymer matrices by cells, layer-by-layer microfluidics can be used to build multilayers of cell-matrix inside a microchannel and the thickness of each layer can be controlled down to microscale dimensions. Confocal and electron microscopy images of the final structure show a hierarchical layered cellular configuration composed of heterogeneous biomimetic materials. For a model system, a biomimetic arterial structure is formed using three types of vascular cells to mimic the 3-tunic structure found in vivo. This approach provides solutions to fabricate hierarchical "neotissues" with controlled microarchitectures and 3-D configurations of multiple cell types.

Biomimetic Materials↗

PubMed2005

Nucleation of biomimetic apatite in synthetic body fluids: dense and porous scaffold development.

The effectiveness of synthetic body fluids (SBF) as biomimetic sources to synthesize carbonated hydroxyapatite (CHA) powder similar to the biological inorganic phase, in terms of composition and microstructure, was investigated. CHA apatite powders were prepared following two widely experimented routes: (1) calcium nitrate tetrahydrate and diammonium hydrogen phosphate and (2) calcium hydroxide and ortophosphoric acid, but using SBF as synthesis medium instead of pure water. The characteristics of the as-prepared powders were compared, also with the features of apatite powders synthesized via pure water-based classical methods. The powder thermal resistance and behaviour during densification were studied together with the mechanical properties of the dense samples. The sponge impregnation process was used to prepare porous samples having morphological and mechanical characteristics suitable for bone substitution. Using this novel synthesis was it possible to prepare nanosized (approximately equal to 20 nm), pure, carbonate apatite powder containing Mg, Na, K ions, with morphological and compositional features mimicking natural apatite and with improved thermal properties. After sintering at 1250 degrees C the carbonate-free apatite porous samples showed a surprising, high compressive strength together with a biomimetic morphology.

Apatites↗

PubMed2005

Electrochemical activation of titanium for biomimetic coating of calcium phosphate.

This article reports an electrochemical method to activate titanium surface for biomimetic calcium phosphate (Ca-P) coatings. Titanium serving as cathode was treated in an electrochemical cell with a supersaturated calcium and phosphate solution serving as electrolyte. This treatment generated a gel-like film with thickness of about 100 nm on the titanium surface. The amorphous film was composed by calcium and phosphate ions and contained a large number of crystal nuclei of octacalcium phosphate (OCP). The effectiveness of this novel treatment was demonstrated by comparing the behavior of treated and untreated titanium when used for biomimetic coating. A uniform Ca-P coating was formed on the treated titanium after immersion for several hours in aqueous solution. This work explored a new method to activate surfaces of metal implants for osseointegration, which is considerably faster than treatments currently in use, such as alkaline treatment.

Biomimetic Materials↗

PubMed2005

Stimulation of osteoblast responses to biomimetic nanocomposites of gelatin-hydroxyapatite for tissue engineering scaffolds.

Collagen-derived gelatin/hydroxyapatite (HA) nanocomposites were biomimetically synthesized for hard tissue engineering scaffold. In vitro osteoblastic cellular responses to the nanocomposites were assessed in comparison with those conventionally mixed gelatin-HA composites. A three-dimensional culture method involving floating cells in a culture medium was introduced to assist in the initial attachment of the cells to the scaffolds, and the proliferation and differentiation behaviors of the cells were examined. The osteoblastic MG63 cells attached to the nanocomposites to a significantly higher degree and subsequently proliferated more. The alkaline phosphatase (ALP) activity and osteocalcin produced by the cells were significantly higher on the nanocomposite scaffolds than on the conventional composite scaffolds. These improved cellular responses on the nanocomposites are considered to result from the increased ionic release and serum protein adsorption on the nanocomposites, which was derived from the different structural and morphological characteristics, i.e., the nanocomposite scaffolds retained less-crystallized and smaller-sized apatite crystals and a more well-developed pore configuration than the conventional ones. Based on these findings, the biomimetically synthesized nanocomposite scaffolds are believed to be potentially useful in hard tissue regeneration and tissue engineering fields.

Alkaline Phosphatase↗

PubMed2006

Biomimetic synthesis of calcium-deficient hydroxyapatite in a natural hydrogel.

A novel composite material consisting of calcium-deficient hydroxyapatite (CdHAP) biomimetically deposited in a bacterial cellulose hydrogel was synthesized and characterized. Cellulose produced by Gluconacetobacter hansenii was purified and sequentially incubated in solutions of calcium chloride followed by sodium phosphate dibasic. A substantial amount of apatite (50-90% of total dry weight) was homogeneously incorporated throughout the hydrogel after this treatment. X-ray diffractometry (XRD) showed that CdHAP crystallites had formed in the cellulose. XRD further demonstrated that the CdHAP was comprised of 10-50 nm anisotropic crystallites elongated in the c-axis, similar to natural bone apatite. Fourier transform infrared (FTIR) spectroscopy demonstrated that hydroxyl IR bands of the cellulose shifted to lower wave numbers indicating that a coordinate bond had possibly formed between the CdHAP and the cellulose hydroxyl groups. FTIR also suggested that the CdHAP had formed from an octacalcium phosphate precursor similar to physiological bone. Scanning electron microscopy (SEM) images confirmed that uniform approximately 1 microm spherical CdHAP particles comprised of nanosized crystallites with a lamellar morphology had formed in the cellulose. The synthesis of the composite mimics the natural biomineralization of bone indicating that bacterial cellulose can be used as a template for biomimetic apatite formation. This composite may have potential use as an orthopedic biomaterial.

Biomimetics↗

PubMed2006

Biomimetic hydrogels for enhanced loading and extended release of ocular therapeutics.

We have applied the principles of biomimesis by incorporating a natural receptor-based rational design strategy in the synthesis of novel recognitive soft contact lenses. We have demonstrated the potential of biomimetic carriers to load significant amounts of ocular medication such as H(1)-antihistamines, as well as to release a therapeutic dosage of drug in vitro in a controlled fashion for 5 days, with an even further extension in the presence of protein. Gels of multiple complexation points with varying functionalities outperformed gels formed with less diverse functional monomers and showed superior loading with a six-fold difference over control gels and a three-fold difference over less biomimetic gels. Moreover, mechanical and optical properties of these hydrogels agreed with conventional lenses, and increased loading was reflected in a reduced propagation of polymer chains. This approach can be extended to a wider biological spectrum in the design of novel, controlled and modulated delivery devices to alleviate ocular disorders and provide an alternative to topical therapy.

Biomimetic Materials↗