Glucose diffusivity in tissue engineering membranes and scaffolds: implications for hollow fibre membrane bioreactor

Unlike thin tissues (e.g., skin) which has been successfully grown, growing thick tissues (e.g., bone and muscle) still exhibit certain limitations due to lack of nutrients (e.g., glucose and oxygen) feeding on cells in extracapillary space (ECS) region, or also known as scaffold in an in vitro static culture. The transport of glucose and oxygen into the cells is depended solely on diffusion process which results in a condition where the cells are deprived of adequate glucose and oxygen supply. This condition is termed as hypoxia and leads to premature cell death. Hollow fibre membrane bioreactors (HFMBs) which operate under perfusive cell culture conditions, have been attempted to reduce the diffusion limitation problem. However, direct sampling of glucose and oxygen is almost impossible; hence noninvasive methods (e.g., mathematical models) have been developed in the past. These models have defined that the glucose diffusivity in cell culture medium (CCM) is similar to the diffusivity in water; thus, they do not represent precisely the nutrient transport processes occurring inside the HFMB. In this research, we define glucose as our nutrient specie due to its limited published information with regard to its diffusivity values, especially one that corresponds to cell/tissue engineering (TE) experiments. A series of well-defined diffusion experiments are carried out with TE materials of varying pore size and shapes imbibed in water and CCM, namely, cellulose nitrate (CN) membrane, polyvinylidene fluoride (PVDF) membrane, poly(L-lactide) (PLLA) scaffold, poly(caprolactone) (PCL) scaffold and collagen scaffold. A diffusion cell is constructed to study the diffusion of glucose across these materials. The glucose diffusion across cell-free membranes and scaffolds is investigated first where pore size distribution, porosity and tortuosity are determined and correlated to the effective diffusivity. As expected, the effective diffusivity increases correspondingly with the pore size of the materials. We also observe that the effective glucose diffusivity through the pores of these materials in CCM is smaller than in water. Next, we seeded human osteoblast cells (HOSTE85) on the scaffolds for a culture period of up to 3 weeks. Similar to the first series of the diffusion experiments, we have attempted to determine the effective glucose diffusivity through the pores of the scaffolds where cells have grown at 37°C. The results show that cell growth changes the morphological structure of the scaffolds, reducing the effective pore space which leads to reduced effective diffusivity. In addition, the self-diffusion of glucose in CCM and water has also been determined using a diaphragm cell method (DCM). The results have shown that the glucose diffusivity in CCM has significantly reduced in comparison to the water diffusivity which is due to the larger dynamic viscosity of CCM. The presence of other components and difference in fluid properties of CCM may also contribute to the decrease. We finally employ our experimentally deduced effective diffusivity and self-diffusivity values into a mathematical model based on the Krogh cylinder assumption. The glucose concentration is predicted to be the lowest near the bioreactor outlet, or in the scaffold region, hence this region becomes a location of interest. The governing transport equations are non-dimensionalised and solved numerically. The results shown offer an insight into pointing out the important parameters that should be considered when one wishes to develop and optimise the HFMB design

Glucose diffusion in tissue engineering membranes and scaffolds

Tissue engineering has evolved into an exciting area of research due to its potential in regenerative medicine. The shortage of organ donor as well as incompatibility between patient and donor pose an alarming concern. This has resulted in an interest in regenerative therapy where the importance of understanding the transport properties of critical nutrients such as glucose in numerous tissue engineering membranes and scaffolds is crucial. This is due to its dependency on successful tissue growth as a measure of potential cure for health issues that cannot be healed using traditional medical treatments. In this regard, the diffusion of glucose in membranes and scaffolds which act as templates to support cell growth must be well grasped. Keeping this in mind, this review paper aims to discuss the glucose diffusivity of these materials. The paper reviews four interconnected issues, namely, (i) the glucose diffusion in tissue engineering materials, (ii) porosity and tortuosity of these materials, (iii) the relationship between microstructure of the material and diffusion and, (iv) estimation of glucose diffusivities in liquids, which determine the effective diffusivities in the porous membranes or scaffolds. It is anticipated that the review paper would help improve the understanding of the transport properties of glucose in membranes and scaffolds used in tissue engineering applications

Glucose diffusivity in cell-seeded tissue engineering scaffolds

Objective: A series of well-defined diffusion experiments was carried out to determine the effective glucose diffusion coefficient in cell-seeded porous scaffolds to understand the importance of nutrient diffusion in tissue engineering bioreactor. Results Cell growth changed the morphological structure of the scaffolds reducing the effective pore space and inevitably decreased the effective glucose diffusivity in the chosen scaffolds, namely, collagen, poly(L-lactide) and poly(caprolactone) scaffolds from 3.71 x 10-9 m2/s to 3.23 x 10-9 m2/s, 1.39 x 10-10 m2/s to 9.09 x 10-11 m2/s and 1.78 x 10-10 m2/s to 1.32 x 10-10 m2/s, respectively. Conclusions The presence of cells over time during cell culture reduces the mobility of glucose. The results of this study should be possible to use to predict the glucose concentration profiles in thick engineered tissues

The Development of an Automated Waste Segregator

Accumulation of waste is a major global concern, and recycling is considered one of the most effective methods to solve the problem. However, recycling requires proper segregation of waste according to waste types. This paper develops an automatic waste segregator, capable of identifying and segregating six types of wastes; metal, paper, plastic, glass, cardboard, and others. The proposed system employs Convolutional Neural Network (CNN) technology, specifically the Inception-v3 architecture, as well as two physical sensors; weight and metal sensors, to classify and segregate the waste. Overall classification accuracy of the system is 86.7%. Classification performance of the developed waste segregator has been evaluated further using the precision and recall; with high precision obtained for cardboard, metal, and other waste types, and high recall for metal and glass. These results demonstrate the applicability of the developed system in effectively segregating waste at source, and thereby, reducing the need for the commonly labor-intensive segregation at waste facility. Deploying the system has the potential of reducing waste management problems by assisting recycling companies in sorting recyclable waste, through automation

The Development of an Automated Waste Segregator

Accumulation of waste is a major global concern, and recycling is considered one of the most effective methods to solve the problem. However, recycling requires proper segregation of waste according to waste types. This paper develops an automatic waste segregator, capable of identifying and segregating six types of wastes; metal, paper, plastic, glass, cardboard, and others. The proposed system employs Convolutional Neural Network (CNN) technology, specifically the Inception-v3 architecture, as well as two physical sensors; weight and metal sensors, to classify and segregate the waste. Overall classification accuracy of the system is 86.7%. Classification performance of the developed waste segregator has been evaluated further using the precision and recall; with high precision obtained for cardboard, metal, and other waste types, and high recall for metal and glass. These results demonstrate the applicability of the developed system in effectively segregating waste at source, and thereby, reducing the need for the commonly labor-intensive segregation at waste facility. Deploying the system has the potential of reducing waste management problems by assisting recycling companies in sorting recyclable waste, through automation

Nutrient transport properties of tissue engineering membranes and scaffolds

There has been an increasing interest in the concept of growing artificial tissues in bioreactors which use numerous membranes and scaffolds to support the cellular processes such as cell growth and nutrient uptake. While these approaches are promising and may be considered to be successful in some circumstances, there is a general lack of quantitative information on the glucose (nutrient) diffusivity of these materials. In addressing this issue we have carried out a series of well-defined laboratory experiments to measure the glucose diffusion coefficient across a number of tissue engineering membranes and scaffolds saturated with water and cell culture medium (CCM). For this purpose, a diffusion cell was constructed and five different membranes and scaffolds with varying pore size and shapes were employed, which include cellulose nitrate membrane, polyvinylidene fluoride membrane, poly(L-lactide) scaffold, poly(caprolactone) scaffold and collagen scaffold. Pore size distribution, porosity and tortuosity of these materials were then determined and correlated to the glucose diffusivity values. As expected, we found that the diffusion coefficient increases with increasing pore size of the materials. These relationships are non-linear and may be non-monotonic in nature as they depend on a number of factors such as the basic building blocks of the materials which are non-periodic and heterogeneous in nature and vary within the same material, or from one material to another. We observed that glucose diffusivities in the materials saturated with CCM are not significantly different at a given temperature. Therefore, a conclusion can be drawn that despite the presence of extra components and difference in fluid properties of CCM compared to water the glucose diffusion coefficient in the tissue engineering membranes and scaffolds are not affected significantly due to the small molecular size of glucose

A Case Study on the Adoption of Cloud Computing in Malaysia from The Perspectives of Cloud Providers

The objective of this study is to discover the perspectives of cloud providers towards cloud computing adoption in Malaysia in terms of the challenges faced by cloud providers and reasons for the adoption. Data were collected through semi structured interviews with three cloud providers. The findings indicated security concern, difficulties in learning cloud computing infrastructure, changes in IT roles, high cost of bandwidth and life span of IT equipment as challenges faced by cloud providers in providing cloud service in Malaysia. This study also discovered cloud scalability, end-to-end management, high level security, and customizable as the reasons on cloud computing adoption. The findings of this study help people to understand more about the current situation of cloud computing adoption in Malaysia. Keywords—cloud adoption, cloud computing, cloud providers, Malaysia

On glucose diffusivity of tissue engineering membranes and scaffolds

There has been an increasing interest in the concept of growing artificial tissues in bioreactors which use numerous membranes and scaffolds to support the cellular processes such as cell growth and nutrient uptake. While these approaches are promising and may be considered to be successful in some circumstances, there is a general lack of quantitative information on the glucose (nutrient) diffusivity of these materials. In addressing this issue we have carried out a series of well-defined laboratory experiments to measure the glucose diffusion coefficient across a number of tissue engineering membranes and scaffolds saturated with water and cell culture medium (CCM). For this purpose, a diffusion cell was constructed and five different membranes and scaffolds with varying pore size and shapes were employed, which include cellulose nitrate membrane, polyvinylidene fluoride membrane, poly(L-lactide) scaffold, poly(caprolactone) scaffold and collagen scaffold. Pore size distribution, porosity and tortuosity of these materials were then determined and correlated to the glucose diffusivity values. As expected, we found that the diffusion coefficient increases with increasing pore size of the materials. These relationships are non-linear and may be non-monotonic in nature as they depend on a number of factors such as the basic building blocks of the materials which are non-periodic and heterogeneous in nature and vary within the same material, or from one material to another. We observed that glucose diffusivities in the materials saturated with CCM are significantly reduced at a given temperature which is contrary to what have been generally assumed in the previous studies on glucose transport processes. Therefore, a conclusion can be drawn that the presence of extra components and difference in fluid properties of CCM compared to water have a significant effect on the glucose diffusion coefficient in the tissue engineering membranes and scaffolds

Illegal vehicles modification: the needs to reform the delegations of enforcement power/ Amier Fitri Abdul Rahim…[et al.]

People usually modified their vehicles with the purpose to make their vehicles to have an outstanding feature. As a result, the vehicle modifications grew to the extent that, it becomes extreme modification. There are certain modifications which are allowed by the authority. However, most of the modification done nowadays is not approve by the authority because they find it is unsuitable and dangerous. This unapproved modification can be regarded as illegal modifications by the authority. The Road Transport Department has identified high number of cases regarding the illegal modified cars and motorcycles in Peninsular Malaysia, which have been compounded. ITic purpose of this research is to study the enforcement conducted by the authority relevant to this matter. This project paper is based on an analysis of the legal statutes on illegal vehicle modifications which have been used as an authority. Our research is concerning a legal study on the need to reform the jurisdiction to enforce the Guidelines of Illegal Vehicles Modifications in Malaysia. Road Transport Act 1987, together with Motor Vehicles (Construction and Use) Regulations 1959 will be analysed as a mechanism in solving illegal vehicle modifications in this country. Our project paper provides the recommendation to reform the jurisdiction to enforce the guidelines of illegal vehicles modifications in Malaysia

Properties of Bio composite Film Based on Whey Protein Isolate Filled with Nanocrystalline Cellulose from Pineapple Crown Leaf

Among the main bio-based polymer for food packaging materials, whey protein isolate (WPI) is one of the biopolymers that have excellent film-forming properties and are environmentally friendly. This study was performed to analyse the effect of various concentrations of bio-based nanocrystalline cellulose (NCC) extracted from pineapple crown leaf (PCL) on the properties of whey protein isolate (WPI) films using the solution casting technique. Six WPI films were fabricated with different loadings of NCC from 0 to 10 % w/v. The resulting films were characterised based on their mechanical, physical, chemical, and thermal properties. The results show that NCC loadings increased the thickness of the resulting films. The transparency of the films decreased at higher NCC loadings. The moisture content and moisture absorption of the films decreased with the presence of the NCC, being lower at higher NCC loadings. The water solubility of the films decreased from 92.2% for the pure WPI to 65.5% for the one containing 10 % w/v of NCC. The tensile strength of the films peaked at 7% NCC loading with the value of 5.1 MPa. Conversely, the trend of the elongation at break data was the opposite of the tensile strength. Moreover, the addition of NCC produced a slight effect of NCC in FTIR spectra of the WPI films using principal component analysis. NCC loading enhanced the thermal stability of the WPI films, as shown by an increase in the glass transition temperature at higher NCC loadings. Moreover, the morphology of the films turned rougher and more heterogeneous with small particle aggregates in the presence of the NCC. Overall, the addition of NCC enhanced the water barrier and mechanical properties of the WPI films by incorporating the PCL-based NCC as the filler