Paraffin Microspheres Research Articles

Preparation of light weight paraffin microspheres based on CO2/N2 switchable emulsion for enhancing plugging performance of drilling fluid

Owing to the synthesis complexity and environmental hazards for the preparation of paraffin sealants by conventional methods, an alternative strategy for paraffin microspheres preparation was still required. Herein, a simplified and economic method based on CO2/N2 switchable paraffin emulsion that was stabilized by surfactant tween-80/span-80 system, was proposed for paraffin microspheres preparation. Paraffin microspheres were obtained upon CO2-induced stability changes of emulsion. The prepared paraffin microsphere has a small mean diameter of 8814.5 nm which meets the demand for the particle size of practical production. With the paraffin microsphere dosage of 0.5%, the mud cake permeability decreased to 50.4%, which indicates the good plugging performance of microspheres. When repeatedly preparing the separated aqueous phase and the recovered emulsion containing dissolved emulsion, it was found that the mean diameter of paraffin microspheres changed slight, which indicates the recyclability of switchable solvent. Paraffin microspheres, as plugging additive, pose remarkable effects on other properties of drilling fluid. It was found that the density decreased from 1.05 g/cm3 to 0.89 g/cm3, AV from 4.0 to 10.50, PV from 1.0 to 7.50, YP from 1.0 to 3.0, and FLAPI decrease continually with the paraffin microspheres dosage increases to 2.5%. The recovery rate of shale is above 80% with the introduction of paraffin microspheres, which indicates that paraffin microspheres emulsion has good compatibility with drilling fluid matrix in a certain range. Herein, a paraffin microspheres preparation method based on CO2/N2 switchable emulsion is also proposed which has wide application in the preparation of paraffin microspheres.

Simple Fabrication and Enhanced Bioactivity of Bioglass‐Poly(lactic‐co‐glycolic acid) Composite Scaffolds with Matrix Microporosity

AbstractScaffold porosity plays an important role in bone tissue engineering as macropores promote cell migration and micropores promote protein adsorption and cell adhesion. Currently, most methods use complex, multi‐step processes to create dual‐scale porosity in composite scaffolds, and no studies evaluate the effect of microporosity on the bioactivity of composite scaffolds with dual porosity. To fill this gap, a simple solvent casting and porogen leaching technique using paraffin microspheres as a porogen and CitriSolv as the leaching solvent to prepare macroporous Bioglass‐poly(lactic‐co‐glycolic acid) (Bg‐PLGA) scaffolds with intrinsic micropores (1–10 µm) in the PLGA matrix is proposed, and the effect of microporosity on the bioactivity of the scaffolds is analyzed. PLGA matrix microporosity induces larger apatite deposition upon immersion in simulated body fluid, as well as enhanced protein adsorption upon contact with serum, compared to non‐microporous scaffolds. Also, mesenchymal cells cultured on the microporous scaffolds show extensive matrix deposition. These results highlight this method as a simple and effective technique to produce dual‐porosity scaffolds that are excellent candidates for bone tissue engineering, as their enhanced bioactivity, protein adsorption, and the extensive matrix deposition observed in‐vitro are good indicators of fast bone integration upon implantation.

EcoFlex Sponge with Ultrahigh Oil Absorption Capacity.

A paraffin microsphere-templated 3D porous EcoFlex sponge was prepared to selectively absorb oil or chemicals from water. The technology for producing this EcoFlex sponge does not need complicated synthesis processes or instruments, and the materials applied in this work are ecofriendly. Therefore, this sponge can be employed in the environmental field. EcoFlex sponges showed high hydrophobicity (contact angle = 140-143°) and oleophilicity. The developed sponge exhibits a porous three-dimensional framework inside with excellent internal connectivity, which contributes both better absorption capacity and faster absorption rate. For instance, the absorption capacity for chloroform can reach3400 wt %. Theabsorption capacity of the sponge was optimized using different size of paraffin microspheres and these sponges exhibit relatively high absorption capacity in a short time (2 min). The volume of sponge expands in some oils and organic solvents: the increased volume capacity for hexane can reach 2200%. This sponge also has great recovery capability and durability; it keeps its original shape and absorption capacity after 15 cycles of oil absorption and compression.

Morphology-Controllable Collagen/Poly(2-hydroxyethyl methacrylate) Porous Hydrogel with a Paraffin Microsphere as a Template.

In this study, a porous poly(2-hydroxyethyl methacrylate) (PHEMA) matrix was fabricated by a paraffin template method, which was used as a substrate to adhere collagen fibers to form an interconnective porous collagen/PHEMA (Col-PHEMA) composite hydrogel. A microscope and scanning electron microscope (SEM) were employed to characterize the morphology of paraffin microspheres and Col-PHEMA composite hydrogels. The paraffin microspheres with the diameter in the range from 100 to 200 μm were collected by a preset sieve. Then, the interface of uniform paraffin microspheres were thermally bonded to form a contacted template, and the derived Col-PHEMA composite hydrogels had an interconnective porous microstructure. Fourier transform infrared spectroscopy (FTIR) indicated that new hydrogen bonds were formed between collagen fibers and the PHEMA hydrogel. Besides, the Col-PHEMA composite hydrogels revealed a high hydrophilicity, good mechanical properties, and good water uptake capacity. The porous Col-PHEMA composite hydrogels showed a good biocompatibility, and the collagen layer may promote the proliferation of fibroblast cells. The Col-PHEMA composite hydrogel is expected to find an application in corneal repairing.

Systematic evaluation of the osteogenic capacity of low-melting bioactive glass-reinforced 45S5 Bioglass porous scaffolds in rabbit femoral defects

Due to the low strength and high brittleness of 45S5 Bioglass®, it is still a great challenge for the three-dimensional porous 45S5 Bioglass® to treat mechanically required loaded bone defects. Therefore, 45S5 Bioglass®-derived bioactive glass-ceramic (BGC) porous scaffolds were fabricated at a low temperature sintering condition with and without the addition of 4% low-melting ZnO/B2O3 (ZB) bioactive glass as a reinforcing agent and using 350- or 500 μm paraffin microspheres as a porogen. The pore structure characterization for the scaffolds indicated that the scaffolds containing 4% ZB had very good macroporous structures of ∼313 and ∼448 μm in pore size and over 70% porosity with appreciable strength (>15 MPa), which was about four times higher than that those manufactured without ZB and with 350 μm porogen scaffolds. The open porosity was decreased with the addition of 4% ZB but the interconnected pore percentage (>50 μm) was increased with increasing the porogen size from 350 to 500 μm. In vivo investigations revealed that the stronger scaffolds containing 4% ZB and 500 μm porogen were particularly beneficial for osteogenic capacity in critical size femoral bone defects, accompanied with an accelerated bone ingrowth (6–18 weeks) and the material itself experiencing mild resorption. In contrast, both the scaffolds with smaller pore sizes exhibited a low level of new bone ingrowth (<32%) after 6–12 weeks implantation. These results suggest a promising application of such 45S5 Bioglass®-derived BGC scaffolds in a clinical setting, especially for mechanically loaded bone defects.

Degradation behavior and compatibility of micro, nanoHA/chitosan scaffolds with interconnected spherical macropores

Hydroxyapatite/Chitosan (HA/CS) composite have significant application in biomedical especially for bone replacement. Inorganic particle shape and size of composite affect the scaffold mechanical property, biological property, and degradation. The aim of this study was to fabricate HA/CS scaffold with good pore connectivity and analyze their biological, degradation properties. Microhydroxyapatite/chitosan (mHA/CS) and nanohydroxyapatite/chitosan (nHA/CS) composite scaffolds with interconnected spherical pore architectures were fabricated. Composite scaffolds structure parameters were analyzed using micro CT. Cell proliferation and morphology were tested and compared between two scaffolds using mouse osteoblastic cell line MC3T3-E1. To research the composite degradation in lysozyme PBS solution, degradation rate and reducing sugar content were tested, and scaffolds morphology were observed by SEM. The results showed that microHA and nanoHA were fabricated by being calcined and synthesis methods, and their infrared spectra are very similar. EDAX composition analysis demonstrated that both of microHA and nanoHA were calcium deficiency HA. Micro-CT results demonstrated the scaffolds had interconnected spherical pores, and the structure parameters were similar. Cell viabilities were significant increased with cultured time, but there were no significant difference between microHA/CS and nanoHA/CS scaffolds. Scaffold structure was gradually destroyed and inorganic composition HA particles are more prominent with degradation time.Significance: (1) Inorganic particle shape and size of composite affect the scaffold mechanical property, biological property, and degradation. NanoHA/CS and microHA/CS scaffolds with good pore connectivity were fabricated and their biological, degradation properties were studied in this manuscript. (2) The scaffold with interconnected porosity construct provides the necessary support for cells to proliferate and maintain their differentiated function, and its architecture related to the structure and morphology of new bone. Polymer scaffolds were fabricated by the technique of compression molding and particulate leaching method, and paraffin microspheres were used as the porogen. (3) MicroHA/CS and nanoHA/CS composite scaffolds are potential materials for use in bone tissue engineering.

A mechanical evaluation of micro-HA/CS composite scaffolds with interconnected spherical macropores.

BackgroundIn the process of bone defective reparation and engineered bone tissue construction, osteoblasts are adhered to the surface of the scaffold materials and impart the external mechanical load to the osteoblasts. So, the dynamic mechanical property of the scaffolds play an important role in the bone tissue repair and it is valuable to research. Material type and the architectural design of scaffolds are also important to facilitate cell and tissue growth. The aim of this study was to prepare a kind of material with good pore connectivity and analyze its dynamic mechanical property.MethodsFabrication and characterization of micro-hydroxyapatite(m-HA)/chitosan(CS) polymer composite scaffolds with well interconnected spherical pore architectures were reports. Micro-HA was prepared by being calcined and ball milled. Paraffin spheres in the range of 160–330 µm were fabricated with a dispersion method and used as the porogen in the fabrication of the scaffolds. Polymer scaffolds were fabricated by the technique of compression molding and particulate leaching method. The effects of the porogen content on the properties of the scaffolds were studied.ResultsWith the increase of porogen, the pore of the scaffolds increased and became interconnected. Cyclic loading of three scaffolds were tested with 10 % strain under four levels of loading frequency, 0.1, 0.5, 1 and 1.5 Hz. The porous composite scaffolds exhibited a viscosity-elastic behaviour with a maximum stress of 3–4 kPa. At each frequency, modulus value is decreased with the paraffin microspheres content, but there was no significance difference in the peak stress of the three samples. All the samples tested displayed clear hysteresis loops. There was no significance difference in the peak hysteresis of the three samples, and the hysteresis difference values between the sixth compression cycle and the initial cycle for three samples was similar, with no statistically significant differences.ConclusionsMicro-HA/CS composite scaffolds with interconnected spherical macropores were fabricated using pherical paraffin as porogen. The porous composite scaffolds exhibited a viscosity-elastic behaviour with good repeatability. It is benefit to study the influence of the mechanical load on the cell of the scaffold.

Effect of processing techniques on the 3D microstructure of poly (l‐lactic acid) scaffolds reinforced with wool keratin from different sources

ABSTRACTThe aim of this work was the analysis of morphologies of poly (l‐lactic acid)/keratin tridimensional scaffolds developed by using two main solvent based techniques: solvent casting particulate leaching in the presence of paraffin microspheres as porogen, and thermally induced phase‐separation process. Keratins from different sources were used. Specifically, keratin from Merino wool (KM) and Brown Alpaca (KA) were dispersed in dioxane or 1,4‐dioxane/water mixture and then the keratin structure after interaction with 1.4‐dioxane was investigated by means of electrophoresis and spectroscopic analysis. A detailed morphological characterization of the scaffold systems obtained by the two different methods was performed by using field emission scanning electron microscopy. The effect of porogen content, solvent composition and processing parameters, such as the influence of keratin presence (1 wt %) and source (KA and KM) were evaluated. The results reveal that 1,4‐dioxane, used as based solvent in the two selected processes, does not negatively affect the keratin structure. A slight change in the procedure parameters, such as porogen content or solvent/non‐solvent ratio, significantly affects the resulting porosity and architecture of the obtained PLLA and PLLA/keratin scaffolds. Both keratins can be considered as suitable fillers able to modify the pore architecture and interconnection of three‐dimensional PLLA/keratin porous composites obtained by the two different solvent assisted techniques. Of note, both composites are biocompatible, as demonstrated by the culture adult bone‐marrow mesenchymal stem cells without signs of toxicity. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42890.

Hydroxyapatite reinforced collagen scaffolds with improved architecture and mechanical properties

Hydroxyapatite (HA) reinforced collagen scaffolds have shown promise for synthetic bone graft substitutes and tissue engineering scaffolds. Freeze-dried HA–collagen scaffolds are readily fabricated and have exhibited osteogenicity in vivo, but are limited by an inherent scaffold architecture that results in a relatively small pore size and weak mechanical properties. In order to overcome these limitations, HA–collagen scaffolds were prepared by compression molding HA reinforcements and paraffin microspheres within a suspension of concentrated collagen fibrils (∼180mg/mL), cross-linking the collagen matrix, and leaching the paraffin porogen. HA–collagen scaffolds exhibited an architecture with high porosity (85–90%), interconnected pores ∼300–400μm in size, and struts ∼3–100μm in thickness containing 0–80vol% HA whisker or powder reinforcements. HA reinforcement enabled a compressive modulus of up to ∼1MPa, which was an order of magnitude greater than unreinforced collagen scaffolds. The compressive modulus was also at least one order of magnitude greater than comparable freeze-dried HA–collagen scaffolds and two orders of magnitude greater than absorbable collagen sponges used clinically. Moreover, scaffolds reinforced with up to 60vol% HA exhibited fully recoverable elastic deformation upon loading to 50% compressive strain for at least 100,000 cycles. Thus, the scaffold mechanical properties were well-suited for surgical handling, fixation, and bearing osteogenic loads during bone regeneration. The scaffold architecture, permeability, and composition were shown to be conducive to the infiltration and differentiation of adipose-derive stromal cells in vitro. Acellular scaffolds were demonstrated to induce angiogenesis and osteogenesis after subcutaneous ectopic implantation by recruiting endogenous cell populations, suggesting that the scaffolds were osteoinductive.

Autonomic Shutdown of Lithium‐Ion Batteries Using Thermoresponsive Microspheres

AbstractAutonomic, thermally‐induced shutdown of Lithium‐ion (Li‐ion) batteries is demonstrated by incorporating thermoresponsive polymer microspheres (ca. 4 μm) onto battery anodes or separators. When the internal battery environment reaches a critical temperature, the microspheres melt and coat the anode/separator with a nonconductive barrier, halting Li‐ion transport and shutting down the cell permanently. Three functionalization schemes are shown to perform cell shutdown: 1) poly(ethylene) (PE) microspheres coated on the anode, 2) paraffin wax microspheres coated on the anode, and 3) PE microspheres coated on the separator. Charge and discharge capacity is measured for Li‐ion coin cells containing microsphere‐coated anodes or separators as a function of capsule coverage. For PE coated on the anode, the initial capacity of the battery is unaffected by the presence of the PE microspheres up to a coverage of 12 mg cm−2 (when cycled at 1C), and full shutdown (&gt;98% loss of initial capacity) is achieved in cells containing greater than 3.5 mg cm−2. For paraffin microspheres coated on the anode and PE microspheres coated on the separator, shutdown is achieved in cells containing coverages greater than 2.9 and 13.7 mg cm−2, respectively. Scanning electron microscopy images of electrode surfaces from cells that have undergone autonomic shutdown provides evidence of melting, wetting, and resolidification of PE into the anode and polymer film formation at the anode/separator interface.

Novel method to produce β-TCP scaffolds

The production of ceramic scaffolds by a novel method was reported in this work. The method comprised the mixture of colloidal silica and β-tricalcium phosphate (β-TCP) powder, where paraffin microspheres were further added to provide the porosity in the scaffold after firing. Thermo-gravimetric analysis showed that the paraffin was completely degraded before 550 °C, where the heat treatment at 1100 °C was enough to remove the paraffin and provide porosity and mechanical strength. The scaffold had an open porosity, but with poor pore interconnection. The density of the scaffold was 1.11 ± 0.03 g/cm 3 with a porosity of 64.98 ± 1.1%, and the compression strength was 5.02 ± 1.2 MPa.

Fabrication and degradation of poly( l-lactic acid) scaffolds with wool keratin

As a natural protein, wool keratin was used to improve the cell affinity of poly( l-lactic acid) (PLLA). Small keratin particles were prepared from keratin solution by the spray-drying process. Keratin particles were blended with PLLA/1,4-dioxane solution and paraffin micro-spheres which were used as progens. After the mixture was molded and dried, the paraffin micro-spheres were removed by cyclohexane. PLLA/keratin scaffolds with controlled pore size and well interconnectivity were fabricated. Keratin releasing rate was detected by Fourier transform infrared (FTIR) after the scaffold was immersed into PBS up to 4 weeks. The surface chemical structure was examined by X-ray photoelectron spectroscope (XPS). The results suggested that the keratin could be held into the scaffold which was expected to improve the interactions between osteoblasts and the polymeric scaffolds.

Hybrid coating of hydroxyapatite and collagen within poly(D,L‐lactic‐co‐glycolic acid) scaffold

To improve the cell-affinity of biodegradable polymer scaffold, coating hydroxyapatite (HA) or collagen on the surface of polymer materials seemed to be a strategy to combine both advantages of them. The objective of this study was to develop a novel method to introduce HA and collagen inside polymer scaffold uniformly. HA and collagen suspension was mixed with paraffin microspheres, and molded to form a composite sample. After the sample was dried, HA/collagen composite was left among and on the surface of paraffin microspheres. Poly(D,L-lactic-co-glycolic acid) (PLGA) (50/50) solution was cast into the inter-space of the paraffin microspheres and dried. Afterwards, the paraffin was dissolved and removed, HA/collagen was transferred to the surface and even inside of the pore wall of PLGA scaffolds. Collagen fibers and HA particles which were inlaid inside the PLGA pore wall could help to enhance the coating strength between HA/Col coating and the pore wall surface of the PLGA scaffold. The scaffolds with HA/Col coating were expected to exhibit desirable properties in bone tissue engineering.

Hydroxyapatite Nano-Particles Coating on the Pore Surface Within Poly(DL-lactic-co-glycolic acid) Scaffold

This paper describes a novel method for coating hydroxyapatite (HA, Ca10(PO4)6(OH)2) nano-particles onto poly(DL-lactic-co-glycolic acid) (PLGA) scaffold. Paraffin micro-spheres were used as porogens to create porous scaffolds and as vehicles to transfer HA into PLGA scaffold. HA nano-particles / 50% ethanol suspension was mixed with paraffin micro-spheres. The paraffin micro-spheres / HA suspension were pressed together to form a paraffin scaffold. After it was dried, the HA was coated on the surface of the paraffin spheres. Then, PLGA solution was cast into the inter space among the paraffin micro-spheres and then the solvent was evaporated. Afterwards, the paraffin micro-spheres were dissolved and removed. PLGA scaffolds with controlled pore size, good interconnectivity and high porosity were obtained. The HA nano-particles were transferred from the paraffin surface to the surface of the pore wall throughout the PLGA scaffold.

Transfer of collagen coating from porogen to scaffold: Collagen coating within poly( dl-lactic-co-glycolic acid) scaffold

Using paraffin micro-spheres as porogen, this paper addressed a novel method to coat collagen onto the internal pore surface within poly( dl-lactic-co-glycolic acid) (PLGA) scaffold with controlled pore size. The paraffin micro-spheres with desirable size were mixed with collagen solution (0.5–1.0% w/v), molded to form a paraffin micro-sphere scaffold, and dried. The collagen was left on the surface of the paraffin micro-spheres and even among the paraffin micro-spheres. PLGA solution was then cast into the interspace of the paraffin/collagen scaffold and dried. After the paraffin micro-spheres were dissolved and removed, PLGA scaffold with controlled pore size, good interconnectivity and high porosity was obtained. Collagen was transferred from the paraffin micro-spheres to the surfaces of the pore wall. Observation of scanning electron microscopy (SEM) showed that collagen was coated on the paraffin micro-spheres and was on the surfaces of pore wall within PLGA scaffold. Fourier transform infrared spectroscopy (FTIR) also detected the presence of collagen in the PLGA scaffold so formed; and there was no apparent change on the molecular components of collagen during the experimental procedure.

Microspheres leaching for scaffold porosity control

Scaffold morphology plays a key role in the development of tissue engineering constructs. The control of pore size, shape and interconnection is needed to achieve adequate nutrient transport and cell ingrowth. Several techniques are available for scaffold manufacturing, but none allows easy control of morphology and is, at the same time, applicable to a wide variety of materials. To investigate the possibility of processing a wide range polymers by solvent casting/particulate leaching with accurate control of scaffold morphology, three different porogens (gelatin microspheres, paraffin microspheres and sodium chloride crystals) were used to fabricate scaffolds from commonly employed biodegradable polymers. The outcome of processing was evaluated in terms of scaffold morphology and structure/properties relationships. Highly porous scaffolds were obtained with all porogens and well defined spherical pores resulted from microspheres leaching. Furthermore, scaffolds with spherical pores showed better mechanical performance and lower flow resistance. Cytocompatibility tests performed showed no evidence of processing residuals released from the scaffolds. Solvent casting/microspheres leaching, particularly gelatin microspheres leaching, can be used to process a large number of polymers and enables to tailor scaffold pore size, shape and interconnection, thus providing a powerful tool for material selection and optimization of scaffold morphology.

Biomimetic Poly(L-Lactic Acid) Scaffolds with Interconnected Macropores, Collagen-Like Nano-Scale Fibers, and Bone-Like Apatite

ABSTRACTHighly porous nano-fibrous poly(L-lactic acid) (PLLA) scaffolds were prepared and incubated in a simulated body fluid which resulted in thein situformation of partially carbonated bone-like apatite. The macroporous interconnected architecture was created with a three-dimensional mold of thermally-bonded paraffin microspheres. PLLA solution was cast over the paraffin mold and was thermally induced to phase separate to form nano-scale fibers that mimic the fibrous structures of type I collagen. To potentially improve the osteoconductivity of these scaffolds, they were incubated in a buffered simulated body fluid at 37°C for certain periods of time to allow for apatite formation. It was seen that over time, the apatite particles increased in size. In addition, the growth of apatite particles on the nano-fibrous scaffolds was compared with the growth of particles on similar porous PLLA scaffolds with a solid-walled (not nano-fibrous) morphology. It was seen that the initial number of particles per unit area and the overall increase in mass of the scaffolds were significantly higher in the nano-fibrous scaffolds than in the solid-walled scaffolds. These novel scaffolds have well-defined architectures at three different size scales: (i) interconnected spherical pores ∼250–400 m in diameter; (ii) fibrous collagen-like matrix with fibers 50–500 nm in diameter; and (iii) carbonated bone-like apatite particles at the nanometer to micrometer scales; the scaffolds may serve as superior support for bone tissue regeneration.