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- Luo, Jun, et al.
(författare)
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In-situ Synchrotron X-ray Diffraction Analysis of the Setting Process of Brushite Cement: Reaction and Crystal Growth
- 2017
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 9:41, s. 36392-36399
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Tidskriftsartikel (refereegranskat)abstract
- Brushite cements are fast self-setting materials that can be used as bone substitute materials. Although tracing their fast setting process is a challenge, it is important for the understanding of the same, which in turn is important for the material’s further development and use in the clinics. In this study, the setting rate, phase formation, and crystal growth of brushite cements were quantitatively studied by in situ synchrotron powder X-ray diffraction (SXRD) on a time scale of seconds. The influence of reactant ratios and a retardant (citric acid) on the setting reaction were analyzed. To complement the in situ investigations, scanning electron microscopy was carried out for ex situ morphological evolution of crystals. The initial reaction followed a four-step process, including a fast nucleation induction period, nucleation, crystal growth, and completion of the setting. The brushite crystal size grew up to the micro scale within 1 min, and the brushite content increased linearly after the nucleation until all monocalcium phosphate monohydrate (MCPM; Ca(H2PO4)2·H2O) had dissolved within minutes, followed by a slow increase until the end of the monitoring. By adjusting the MCPM to the β-tricalcium phosphate (β-TCP, β-Ca3(PO4)2) ratio in the starting powders, the brushite/monetite ratio in the cements could be modified. In the presence of citric acid, the formation of brushite nuclei was not significantly retarded, whereas the increase in brushite content and the growth of crystal size were effectively hindered. The amount of monetite also increased by adding citric acid. This is the first time that the brushite setting process has been characterized in the first seconds and minutes of the reaction by SXRD.
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- Yang, Jiaojiao
(författare)
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Amorphous magnesium carbonate nanomaterials : Synthesis, characterization and applications
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- High surface-to-volume ratio materials, including nanoparticles and mesoporous materials, have a number of applications due to their large surface area and special structures. Traditional approaches for synthesizing high surface-to-volume ratio nanomaterials are often complicated, expensive or environmentally unfriendly. Considering aspects such as availability and safety in terms of environmental or biological contact, magnesium carbonate-based nanomaterials are an interesting and potentially valuable candidate for novel applications. The overall aim of this thesis was to develop novel high surface-to-volume ratio amorphous magnesium carbonate nanomaterials and investigating their possible applications.Amorphous magnesium carbonate nanoparticles (AMN) were successfully synthesized via a simple and low-temperature pathway. The structure and resulting properties of the material can be tailored by changing the final steps in the synthesis process.The ability of AMN to stabilize ibuprofen (IBU) in the amorphous state was investigated. Nanocomposites with IBU:AMN mass ratios as high as to 5:1 were shown to enhance the release rate of IBU in vitro by as much as 83 times compared to IBU in crystalline form. A related nanostructured material, mesoporous magnesium carbonate (MMC), was evaluated as a drug carrier for stabilizing amorphous drugs through the incorporation of the drug within its pores. In this study, MMC was used to release and sustain two poorly soluble drugs (tolfenamic acid and rimonabant) in the supersaturated state with the assistance of hydroxypropyl methylcellulose.AMN was also used to synthesize a novel adhesive together with IBU without the addition of a polymer. This adhesive was transparent, self-healing, shapeable, stretchable and reusable. In addition, the adhesive was able to glue a variety of materials, including metals, glass, paper and plastics (even Teflon).Finally, AMN was used to prepare flexible, transparent and UV-shielding films when incorporated into a PMMA matrix. These films exhibited both UV-shielding properties and moisture absorbance and retention abilities. In addition, the UV- and thermo-stability of these films were enhanced by the addition of AMN.The work presented in this thesis show that the nanomaterials AMN and MMC possess great potential for an extremely broad range of applications, from pharmaceutical applications dealing with poorly soluble drugs to structural applications such as adhesives to applications in optics or electronics such as UV-shielding or moisture barrier films.
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- Yang, Jiaojiao, et al.
(författare)
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Amorphous Magnesium Carbonate Nanoparticles with Strong Stabilizing Capability for Amorphous Ibuprofen
- 2018
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Ingår i: International Journal of Pharmaceutics. - : Elsevier. - 0378-5173 .- 1873-3476. ; 548:1, s. 515-521
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Tidskriftsartikel (refereegranskat)abstract
- Formulating active pharmaceutical ingredients (APIs) in the amorphous state can increase their apparent aqueous solubility and dissolution rate and consequently improve their bioavailability. This study demonstrates, for the first time, the ability to stabilize an API in the amorphous state using a solid dispersion of magnesium carbonate nanoparticles within the API. Specifically, high proportions of ibuprofen were able to be stabilized in the amorphous state using as little as 17% wt/wt amorphous magnesium carbonate nanoparticles, and drug release rates 83 times faster than from the crystalline state were achieved. Biocompatibility of the nanoparticles was demonstrated in vitro using human dermal fibroblasts and stability of the nanocomposite formulation was verified with a storage time of six months. The success of this novel formulation provides a promising approach for achieving improved apparent solubility and enhanced bioavailability of drugs.
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- Yang, Jiaojiao, et al.
(författare)
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Electrochemically Active, Compressible, and Conducting Silk Fibroin Hydrogels
- 2020
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Ingår i: Industrial & Engineering Chemistry Research. - : AMER CHEMICAL SOC. - 0888-5885 .- 1520-5045. ; 59:19, s. 9310-9317
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Tidskriftsartikel (refereegranskat)abstract
- Silk fibroin-based conducting hydrogels possess hierarchical structural motifs featuring unique properties, but the development of such materials has proven to be challenging. Herein, we develop a novel strategy for the fabrication of a conducting silk fibroin hydrogel based on an interpenetrated network of poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and silk fibroin. The hydrogel possesses good electrical conductivity and considerable capacitance and cycling stability due to the existence of the PEDOT conducting network, as well as enhanced mechanical properties such as compressibility due to beta-sheets in the silk fibroin network and Ca2+ cross-linking of the PSS components. A symmetric charge storage device based on conductive silk fibroin hydrogel electrodes exhibited a remarkable areal capacitance of 1.1 F cm(-2) at 0.5 mA cm(-2), as well as a good capacitive response under a compressed state. This combination of compression strength and electrochemical properties makes this conducting silk hydrogel a potential material for unconventional energy storage applications.
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- Yang, Jiaojiao, et al.
(författare)
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Enhanced release of poorly water-soluble drugs from synergy between mesoporous magnesium carbonate and polymers
- 2017
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Ingår i: International Journal of Pharmaceutics. - : Elsevier BV. - 0378-5173 .- 1873-3476. ; 525:1, s. 183-190
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Tidskriftsartikel (refereegranskat)abstract
- The need to combat poor water solubility has increased interest in supersaturating drug delivery systems. In this study, amorphous mesoporous magnesium carbonate (MMC) was used as a drug carrier to achieve supersaturation of tolfenamic acid and rimonabant, two drug compounds with low aqueous solubility. The potential synergy between MMC and hydroxypropyl methylcellulose (HPMC), a polymer commonly included as a precipitation inhibitor in drug delivery systems, was explored with the aim of extending the time that high supersaturation levels were maintained. Release was studied under physiological conditions using USP-2 dissolution baths. A new small-scale method was developed to enable measurement of the initial drug release occurring when the MMC is immersed in the water phase. It was shown that MMC and HPMC together resulted in significant supersaturation and that the polymer enabled both the achievement of a higher API concentration and extension of the supersaturation period. The new small-scale release method showed that the release was linearly increasing with the dose and that similar release rates were observed for the two model compounds. It was hence concluded that the MMC release was diffusion limited for the compounds explored.
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