Development of gelatin/carboxymethyl chitosan/nano-hydroxyapatite composite 3D macroporous scaffold for bone tissue engineering applications

The present study delineates a relatively simpler approach for fabrication of a macroporous three-dimensional scaffold for bone tissue engineering. The novelty of the work is to obtain a scaffold with macroporosity (interconnected networks) through a combined approach of high stirring induced foaming of the gelatin/carboxymethyl chitosan (CMC)/nano-hydroxyapatite (nHAp) matrix followed by freeze drying. The fabricated macroporous (SGC) scaffold had a greater pore size, higher porosity, higher water retention capacity, slow and sustained enzymatic degradation rate along with higher compressive strength compared to that of non-macroporous (NGC, prepared by conventional freeze drying methodology) scaffold. The biological studies revealed the increased percentage of viability, proliferation, and differentiation as well as higher mineralization of differentiated human Wharton's jelly MSC microtissue (wjhMSC-MT) on SGC as compared to NGC scaffold. RT-PCR also showed enhanced expression level of collagen type I, osteocalcin and Runx2 when seeded on SGC. μCT and histological analysis further revealed a penetration of cellular spheroid to a greater depth in SGC scaffold than NGC scaffold. Furthermore, the effect of cryopreservation on microtissue survival on the three-dimensional construct revealed significant higher viability upon revival in macroporous SGC scaffolds. These results together suggest that high stirring based macroporous scaffolds could have a potential application in bone tissue engineering.

Biomimetic fiber mesh scaffolds based on gelatin and hydroxyapatite nano-rods: Designing intrinsic skills to attain bone reparation abilities

Intrinsic material skills have a deep effect on the mechanical and biological performance of bone substitutes, as well as on its associated biodegradation properties. In this work we have manipulated the preparation of collagenous derived fiber mesh frameworks to display a specific composition, morphology, open macroporosity, surface roughness and permeability characteristics. Next, the effect of the induced physicochemical attributes on the scaffold's mechanical behavior, bone bonding potential and biodegradability were evaluated. It was found that the scaffold microstructure, their inherent surface roughness, and the compression strength of the gelatin scaffolds can be modulated by the effect of the cross-linking agent and, essentially, by mimicking the nano-scale size of hydroxyapatite in natural bone. A clear effect of bioactive hydroxyapatite nano-rods on the scaffolds skills can be appreciated and it is greater than the effect of the cross-linking agent, offering a huge perspective for the upcoming progress of bone implant technology.

Incorporation of fast dissolving glucose porogens and poly(lactic-co-glycolic acid) microparticles within calcium phosphate cements for bone tissue regeneration

This study investigated the effects of incorporating glucose microparticles (GMPs) and poly(lactic-co-glycolic acid) microparticles (PLGA MPs) within a calcium phosphate cement on the cement's handling, physicochemical properties, and the respective pore formation. Composites were fabricated with two different weight fractions of GMPs (10 and 20 wt%) and two different weight fractions of PLGA MPs (10 and 20 wt%). Samples were assayed for porosity, pore morphology, and compressive mechanical properties. An in vitro degradation study was also conducted. Samples were exposed to a physiological solution for 3 days, 4 wks, and 8 wks in order to understand how the inclusion of GMPs and PLGA MPs affects the composite's porosity and mass loss over time. GMPs and PLGA MPs were both successfully incorporated within the composites and all formulations showed an initial setting time that is appropriate for clinical applications. Through a main effects analysis, we observed that the incorporation of GMPs had a significant effect on the overall porosity, mean pore size, mode pore size, and in vitro degradation rate of PLGA MPs as early as after 3 days (p < 0.05). After 4 wks and 8 wks, these same properties were affected by the inclusion of both types of MPs (p < 0.05). Advanced polymer chromatography confirmed that the degradation of PLGA MPs coincided with an increase in composite porosity, mean pore size, and mode pore size. Finally, it was observed that the inclusion of GMPs slowed the degradation of PLGA MPs in vitro and reduced the solution acidity due to PLGA degradation products. Our results suggest that the dual inclusion of GMPs and PLGA MPs is a valuable approach for the generation of early macropores, while also mitigating the effect of acidic degradation products from PLGA MPs on their degradation kinetics.

STATEMENT OF SIGNIFICANCE

A multitude of strategies and techniques have been investigated for the introduction of macropores with calcium phosphate cements (CPC). However, many of these strategies take several weeks to months to generate a maximal porosity or the degradation products of the porogen can trigger a localized inflammatory response in vivo. As such, it was hypothesized that the fast dissolution of glucose microparticles (GMPs) in a CPC composite also incorporating poly(lactic-co-glycolic acid) (PLGA) microparticles (MPs) will create an initial macroporosity and increase the surface area within the CPC, thus enhancing the diffusion of PLGA degradation products and preventing a significant decrease in pH. Furthermore, as PLGA degradation occurs over several weeks to months, additional macroporosity will be generated at later time points within CPCs. The results offer a new method for generating macroporosity in a multimodal fashion that also mitigates the effects of acidic degradation products.

Improved method for effective rock microporosity estimation using X-ray microtomography

Petrophysical analysis using X-ray microtomography provides key textural and compositional information, useful to investigate porous media characteristics of hydrocarbon and geothermal reservoirs. Several approaches, used for rock porosity estimation from tomography data, rely mainly on visual or mathematical segmentation algorithms that attempt to obtain thresholding values to segment a phase solved by pixel analysis resolution. Therefore, porosity is evaluated using only pores above pixel resolution (macroporosity), and dismiss pores sized less than the pixel resolution (microporosity) that can be essential to characterize permeability conditions of geothermal reservoirs. Here we propose an improved method to calculate the total effective porosity and simulate the absolute permeability of rock samples. This method combines the analysis of X-ray computed microtomography (μCT) with the interpretation of data using a powerful thresholding method that is based on the greyscale interclass variance. The 3D volume is segmented into three domains: solid, pores above resolution and, an intermediate region where each pore below resolution is linearly combined with solid matrix resulting in a grey scaled pixel equal to this combination. For the intermediate region, the microporosity was calculated employing a Matlab code that provides a new thresholding value containing pores, both above and below resolution (total porosity). Finally, by using this new calculated thresholding value the total effective porosity was obtained and an absolute permeability simulation was implemented only to the connected pores. Our results show that micropores contribute for nearly 50 percent of the total porosity and that microporosity plays a key role in estimating effective porosity, and assessing the geothermal potential of a rock reservoir.

Assessing the long-term effects of zero-tillage on the macroporosity of Brazilian soils using X-ray Computed Tomography

Zero-tillage (ZT) is being increasingly adopted globally as a conservationist management system due to the environmental and agronomic benefits it provides. However, there remains little information on the tillage effect on soil pore characteristics such as shape, size and distribution, which in turn affect soil physical, chemical and biological processes. X-ray micro Computed Tomography (μCT) facilitates a non-destructive method to assess soil structural properties in three-dimensions. We used X-ray μCT at a resolution of 70 μm to assess and calculate the shape, size and connectivity of the pore network in undisturbed soil samples collected from a long-term experiment (~30 years) under zero tillage (ZT) and conventional tillage (CT) systems in Botucatu, Southeastern Brazil. In both systems, a single, large pore (>1000 mm³) typically contributed to a large proportion of macroporosity, 91% in CT and 97% in ZT. Macroporosity was higher in ZT (19.7%) compared to CT (14.3%). However the average number of pores was almost twice in CT than ZT. The largest contribution in both treatments was from very complex shaped pores, followed by triaxial and acircular shaped. Pore connectivity analysis indicated that the soil under ZT was more connected that the soil under CT. Soil under CT had larger values of tortuosity than ZT in line with the connectivity results. The results from this study indicate that long-term adoption of ZT leads to higher macroporosity and connectivity of pores which is likely to have positive implications for nutrient cycling, root growth, soil gas fluxes and water dynamics.

Environmental and management influences on temporal variability of near saturated soil hydraulic properties

Structural porosity is a decisive property for soil productivity and soil environmental functions. Hydraulic properties in the structural range vary over time in response to management and environmental influences. Although this is widely recognized, there are few field studies that determine dominant driving forces underlying hydraulic property dynamics. During a three year field experiment we measured temporal variability of soil hydraulic properties by tension infiltrometry. Soil properties were characterized by hydraulic conductivity, effective macroporosity and Kosugi's lognormal pore size distribution model. Management related influences comprised three soil cover treatment (mustard and rye vs. fallow) and an initial mechanical soil disturbance with a rotary harrow. Environmental driving forces were derived from meteorological and soil moisture data. Soil hydraulic parameters varied over time by around one order of magnitude. The coefficient of variation of soil hydraulic conductivity K(h) decreased from 69.5% at saturation to 42.1% in the more unsaturated range (- 10 cm pressure head). A slight increase in the Kosugi parameter showing pore heterogeneity was observed under the rye cover crop, reflecting an enhanced structural porosity. The other hydraulic parameters were not significantly influenced by the soil cover treatments. Seedbed preparation with a rotary harrow resulted in a fourfold increase in macroporosity and hydraulic conductivity next to saturation, and homogenized the pore radius distribution. Re-consolidation after mechanical loosening lasted over 18 months until the soil returned to its initial state. The post-tillage trend of soil settlement could be approximated by an exponential decay function. Among environmental factors, wetting-drying cycles were identified as dominant driving force explaining short term hydraulic property changes within the season (r² = 0.43 to 0.59). Our results suggested that beside considering average management induced changes in soil properties (e.g. cover crop introduction), a dynamic approach to hydrological modeling is required to capture over-seasonal (tillage driven) and short term (environmental driven) variability in hydraulic parameters.

Environmental and management influences on temporal variability of near saturated soil hydraulic properties

Structural porosity is a decisive property for soil productivity and soil environmental functions. Hydraulic properties in the structural range vary over time in response to management and environmental influences. Although this is widely recognized, there are few field studies that determine dominant driving forces underlying hydraulic property dynamics. During a three year field experiment we measured temporal variability of soil hydraulic properties by tension infiltrometry. Soil properties were characterized by hydraulic conductivity, effective macroporosity and Kosugi's lognormal pore size distribution model. Management related influences comprised three soil cover treatment (mustard and rye vs. fallow) and an initial mechanical soil disturbance with a rotary harrow. Environmental driving forces were derived from meteorological and soil moisture data. Soil hydraulic parameters varied over time by around one order of magnitude. The coefficient of variation of soil hydraulic conductivity K(h) decreased from 69.5% at saturation to 42.1% in the more unsaturated range (- 10 cm pressure head). A slight increase in the Kosugi parameter showing pore heterogeneity was observed under the rye cover crop, reflecting an enhanced structural porosity. The other hydraulic parameters were not significantly influenced by the soil cover treatments. Seedbed preparation with a rotary harrow resulted in a fourfold increase in macroporosity and hydraulic conductivity next to saturation, and homogenized the pore radius distribution. Re-consolidation after mechanical loosening lasted over 18 months until the soil returned to its initial state. The post-tillage trend of soil settlement could be approximated by an exponential decay function. Among environmental factors, wetting-drying cycles were identified as dominant driving force explaining short term hydraulic property changes within the season (r² = 0.43 to 0.59). Our results suggested that beside considering average management induced changes in soil properties (e.g. cover crop introduction), a dynamic approach to hydrological modeling is required to capture over-seasonal (tillage driven) and short term (environmental driven) variability in hydraulic parameters.

Long-term impact of reduced tillage on water and pesticide flow in a drained context

Influence of more than 20 years (1988-2010) of reduced tillage (RT) practices on water and pesticide balances and dynamics is analyzed and compared to results from a conventional tillage plot (CT). The field study soils are described as silty clay stagnic luvisol, developed on a low permeable schist layer. A drainage network was set up according to French criteria (0.9 m deep, 10 m space) to avoid soil winter waterlogging. Climate is temperate oceanic and drainage generally occurs from November to March. Data were analyzed at yearly, weekly (pesticides) and hourly (water) time steps. Over the long term, cumulated drainage decreases significantly on RT (3999 mm) compared to CT (5100 mm). This differentiation becomes significant from 1999, 10 years after plowing was stopped. Strikingly, hourly drainage peak flows are higher under RT, especially during the second period (2000-2010), associated with low or no base flow. These results suggest a strong influence of the macropore network under RT practice. In particular, drainage peaks are higher at the beginning of the drainage season (mid-October to December). Consistently, pesticides applied in late autumn, which are the most quantified on this site, are often significantly more exported under RT. For atrazine, applied in spring, fluxes are linked to cumulative flow and are de facto higher under CT. For others pesticides, losses appear to be heterogeneous, with generally low or null export rates for spring application. Generally speaking, higher concentrations are measured on RT plot and explain observed exportation rate differences. Finally, there is no clear evidence of correlation between pesticide losses and long-term impacts of RT on hydrodynamics, pointing the importance of studying the short-term effect of tillage on water and especially solute flow.

Characterization of preferential flow in soils near Zarqa river (Jordan) using in situ tension infiltrometer measurements

Background

The Zarqa River (ZR) is located in the northern part of Jordan and supplies King Talal Dam (KTD). The streamflow that discharges into KTD is composed of treated wastewater from the Khirbat Es-Samra water treatment plant (KTP) and runoff generated during the winter season. Thus, during the summer, the streamflow of the ZR is dominated by effluent from the KTP. Due to the severe scarcity of water in Jordan, a portion of the streamflow is utilized for irrigated agriculture in the ZR valley, located between the KTP and KTD. The groundwater in the vicinity of the ZR is vulnerable to contamination—a risk that may be exacerbated by the potential occurrence of preferential flow (PF). Therefore, the PF in the soils near the ZR should be carefully considered.

Methods

The macropore flux fraction (Q_macro) and macroscopic capillary length (λ_c) were determined from in situ measurements using a tension infiltrometer equipped with an infiltration disc with a diameter of 20 cm. The macropore was defined as the pore size that drains at a tension of less than —-3— cm. The λ_c less than 80 mm was considered to be an indication of PF. The measurements were taken at 69 sites along the ZR between the KTP and KTD. At each measurement site, the soil organic matter content (OM) and soil texture were determined using a composite soil sample obtained by excavating the soil beneath the infiltration disc to a depth of 10 cm.

Results

The data was split into two groups: the matrix flow group (MF), which includes data associated with λ_c > 80 mm, and the PF group, which includes data associated with λ_c < 80 mm. The Q_macro values of 0.67 and 0.57, respectively, for PF and MF were significantly different at p < 0.01 (t-test). The flow rates at h=0 were generally well associated with λ_c, as attested to by a significant difference between the averages of PF (57.8 mm/hr) and MF (21.0 mm/hr) at p < 0.01 (t-test). The OM was positively associated with PF. This was statistically confirmed by a t-test at p < 0.01. The average sand and clay contents of PF and MF were not statistically different. Analysis of the ratio of Soil Organic Carbon (SOC) to clay showed that the average SOC/clay of the PF (14%) was larger than that of the MF (13.3%). After the exclusion of soils with clay content less than 8%, the differences between the SOC/clay averages of PF (9.8%) and MF (7.5%) were significant at p < 0.05, as shown by a WM-test.

Conclusion

The OM was positively associated with PF. Soil texture—and clay content in particular—influenced the λ_cvalues. However, the association of clay content with PF was not statistically significant. Consideration of the SOC/clay ratio showed that the tendency toward PF increases as the complexation of the clay content increases. This was most obvious in soils with a clay content of greater than 8% and SOC/clay of approximately 10%. The OM either influences or is inter-correlated with the processes responsible for the formation of macropores.

Fluidic embedding of additional macroporosity in alginate-gelatin composite structure for biomimetic application

Biomimetic characteristics of hydrogel scaffold are tuned in this study utilizing the synergy of alginate, gelatin, and microfluidically embedded voids. Superposition of alginate and gelatin polymer networks results in additional rigidity, which can be tuned by introduction of voids, and thereby allowing faster release of pore pressure through movement of aqueous phase through the pore network. More importantly, voids enabled the cells to penetrate from the surface of seeding into the depth of the scaffold and proliferate there, as demonstrated for MDA MB 231 breast cancer cells. The uniform voids, generated by the microfluidic device, self-align creating uniform macroporosity within the gel structure, get readily filled by the media due to hydrophilicity, and extend the characteristics of composite uniformly across the entire scaffold.

Age Estimation of Lumbar Vertebrae by Visual Assessment in a Thai Population

BACKGROUND

The age estimation of bone is essential for identification of the unknown-identity persons in both forensic and anthropological sciences. The lumbar vertebrae carry the most weight; hence, they have more biomechanical stress than any other vertebrae. As a result, the degenerative changes commonly occur in them. However, the estimation from visual assessment in lumbar vertebrae has not been reported in a Thai population.

OBJECTIVE

To evaluate the age estimation from the degree of osteophyte formation, the macroporosity, and the cortical surface to develop equations of lumbar vertebrae.

MATERIALS AND METHODS

A total of 250 lumbar columns (125 males and 125 females) in age range of 22 to 89 years were collected from the Forensic Osteology Research Center (FORC), Faculty of Medicine, Chiang Mai University.

RESULT

The most appropriate linear regression equation was used to estimate age by the inferior surface of L1 vertebra (R2= 0.408) with the standard error of 11.686 years.

CONCLUSION

It was clear to recognize that three morphological aspects will be useful methods for forensic situations.