M. Nuruzzaman Khan

Mechanical, Degradation, and Interfacial Properties of Synthetic Degradable Fiber Reinforced Polypropylene Composites

Polypropylene (PP) matrix synthetic phosphate based degradable fiber reinforced unidirectional composites (10% fiber by weight) were fabricated by compression molding. Tensile strength (TS), tensile modulus (TM), elongation at break (%), bending strength (BS), bending modulus (BM), and impact strength (IS) were found to be 38 MPa, 1.5 GPa, 12%, 44 MPa, 4.9 GPa, and 7.58 kJ/m 2 respectively. Degradation tests of the fibers and composites were performed for six months in aqueous medium at room temperature (25°C). After six months, the mechanical properties of the composites retained almost 80% of their original properties. The interfacial shear strength (IFSS) of the composites were also measured by single fiber fragmentation test (SFFT). The IFSS of the composite system was found 5.9 MPa that indicated good fiber matrix adhesion.

Fabrication and characterization of gelatin-based biocompatible porous composite scaffold for bone tissue engineering †

In this study, composite scaffolds were prepared with polyethylene oxide (PEO)-linked gelatin and tricalcium phosphate (TCP). Chitosan, a positively charged polysaccharide, was introduced into the scaffolds to improve the properties of the artificial bone matrix. The chemical and thermal properties of composite scaffolds were investigated by Fourier transform infrared spectroscopy, thermogravimetric analyzer, differential thermal analyzer. In vitro cytotoxicity of the composite scaffold was also evaluated and the sample showed no cytotoxic effect. The morphology was studied by SEM and light microscopy. It was observed that the prepared scaffold had an open interconnected porous structure with pore size of 230-354 μm, which is suitable for osteoblast cell proliferation. The mechanical properties were assessed and it was found that the composite had compressive modulus of 1200 MPa with a strength of 5.2 MPa and bending modulus of 250 MPa having strength of 12.3 MPa. The porosity and apparent density were calculated and it was found that the incorporation of TCP can reduce the porosity and water absorption. It was revealed from the study that the composite had a 3D porous microstructure and TCP particles were dispersed evenly among the crosslinked gelatin/chitosan scaffold.

Fabrication of ssDNA/Oligo(ethylene glycol) Monolayers and Complex Nanostructures by an Irradiation‐Promoted Exchange Reaction

The macromolecular structure of DNA, its ability to hybridize, the diversity of non-natural nucleotides with unique functional groups that are available to perform chemistry on it, and enzymes that are capable of manipulating its sequence, structure, and topology provide rich opportunities for its use in clinical diagnostics, biosensors, gene therapy, and drug delivery. Some of these applications rely on the immobilization of single-stranded DNA (ssDNA) onto a solid support, which is subsequently used for binding and detection of its complementary ssDNA target or for the recognition of DNA binding proteins. A commonly used method for immobilization of ssDNAs is to functionalize them with a terminal reactive group that is selective for the surface of interest. Depending on the particular application, immobilization can be performed either homogeneously over the entire surface or lithographically, resulting in an array of ssDNA spots. The hybridization activity of supported ssDNA depends on the packing density and molecular organization, which can be manipulated by diluting ssDNAwith other molecules that have the same reactive group. For a gold substrate, the diluent molecules of choice are short-chain alkanethiols (ATs) or thiolated oligo(ethylene glycol)s (OEGATs). OEG-ATs are especially attractive for applications in which the DNA comes into contact with complex biological fluids because of their ability to resist the adsorption of proteins. Strategies to prepare such mixed films include co-deposition, backfilling, and postdeposition by substitution. In an alternative approach, ssDNA can be covalently conjugated to a terminal reactive functional group presented by the monolayer. OEGATs are also frequently used to provide a protein-repelling background to ssDNA patterns. These patterns are usually prepared by one of the standard techniques such as microcontact printing, UV lithography, or drop casting by a syringe or microarrayer. The preparation of the OEG-ATs background typically occurs by backfilling after deposition of the ssDNA on the surface. Herein, we present a new and potentially universal approach to prepare both mixed ssDNA/OEG-AT films in a broad range of compositions and ssDNA/OEG-AT patterns of arbitrary form. We demonstrate the strength of the approach by combining it with surface-initiated enzymatic polymerization (SIEP) and sculpting complex DNA nanostructures. This approach is based on an irradiation-promoted exchange reaction (IPER) and electron-beam lithography (EBL). Generally, IPER gives control over the extent and rate of the molecular exchange between the primary monolayer and a potential substituent by electron irradiation of the monolayer with a suitable dose. It works well with a monolayer comprised of methyl-terminated, short-chain ATs, but is difficult to apply to OEG-ATs films, because of the inefficiency of promoted exchange (the molecules are too long) and contrast deterioration owing to non-promoted exchange occurring frequently in these systems. However, IPER works well with thiolated ssDNA as the substituent. The procedure is illustrated in Figure 1a. A primary monolayer of a test OEG-AT compound, HO(CH2CH2O)3(CH2)11SH (termed EG3; see Refs. [28] and [29] for its protein-resistance) was homogeneously irradiated with electrons or using EBL, resulting in preferential damage of the OEG chain parts and cleavage of thiolate–gold bonds. Next, the film was incubated with a solution of a model thiolated homo-oligonucleotide, 5’-SH-(CH2)6d(A)25-3’ (termed A25SH) for the exchange reaction promoted by the irradiation defects. We used EBL to visually demonstrate the efficiency of IPER in substituting A25SH in an EG3 matrix. AFM clearly shows the formation of a nanoscale A25SH pattern against a background of the EG3 that spells “DNA” (Figure 1c and Supporting Information, Figure S1). The proportion of the A25SH component in the mixed A25SH/EG3 monolayer can be precisely controlled by selection of the irradiation dose. As shown in Figure 2a, N1s photoemission (PE) spectra of the one-component A25SH monolayer and mixed A25SH/EG3 films prepared by IPER exhibit the characteristic two-peak signature of adenine at 399.3 and 401.1 eV and the intensity of this signal increases with increasing irradiation dose, demonstrat[*] M. N. Khan, Prof. Dr. M. Zharnikov Angewandte Physikalische Chemie, Universit t Heidelberg Im Neuenheimer Feld 253, Heidelberg (Germany) E-mail: Michael.Zharnikov@urz.uni-heidelberg.de Homepage: http://www.pci.uni-heidelberg.de/apc/zharnikov/

Preparation and Mechanical Characterization of Gelatin-Based Films Using 2-Hydroxyethyl Methacrylate Cured by UV Radiation

Gelatin films were prepared from gelatin granules in aqueous medium by casting. Tensile strength, tensile modulus and elongation at break of the gelatin films were found to be 27 MPa, 100 MPa and 4%, respectively. Gelatin films were soaked in five different formulations containing 2-hydroxyethyl methacrylate (HEMA) (10–50%, by wt), methanol and photoinitiator and then cured under UV radiation. Again, a series of gelatin solutions was prepared by blending varying percentages (10–50% by wt) of HEMA and then films were prepared and UV cured. It was found that tensile properties of gelatin films improved significantly.

Thermomechanical and Interfacial Properties of Calcium Alginate Fiber-Reinforced Polypropylene Composites

Polypropylene (PP) matrix calcium alginate fiber reinforced unidirectional composites (10% fiber by weight) were fabricated by compression molding. Tensile strength (TS), tensile modulus (TM), bending strength (BS), bending modulus (BM), and impact strength (IS) were found to be 26 MPa, 950 MPa, 38 MPa, 1320 MPa, and 20 kJ/m2, respectively. Degradation tests of composites were performed for 6 weeks in soil and it was found that composites retained almost 75% of its original strength. The interfacial properties of the composite were investigated by using single fiber fragmentation test (SFFT) and by scanning electron microscope (SEM).

Recent Updates on Immobilization of Microbial Cellulase

Several new types of carriers and techniques have been implemented in recent years to improve the traditional cellulase immobilization process, which aims to enhance its loading, activity, and stability with reduced cost for various industrial applications. This chapter summarizes the recent advancements in all aspects of microbial cellulase enzyme like the types of cellulases, their microbial sources, structure, and properties, immobilization factors, and industrial applications. Common cellulase inducers and existing immobilization matrices are highlighted along with insights into the recent developments for each of them. Different immobilization techniques, the types of reactors used so far, and their effect on the immobilized cellulase are thoroughly discussed. More importantly, this review focuses on the future immobilization processes of cellulase and their potential for the most modern industrial applications.

Cellulase in Waste Management Applications

Our society produces a lot of voluminous waste of biomass every day, which are mainly lignocellulose in origin. It is the most abundant plant cell wall component of the biosphere and the most plentiful biological compound on terrestrial earth. The successful conversion of cellulosic waste from domestic, industrial, and municipal sources through economically feasible processes to valuable by-products has long been admitted as a desirable endeavor. The degradation of cellulosic materials has gained increasing attention due to its worldwide availability and enormous potential for transforming them into sugars, fuels, and chemical feedstocks. Enzymatic hydrolysis of cellulosic biomass holds tremendous promise due to the high specificity and production of high yields of glucose without generation of degradation products, unlike acid/alkali hydrolysis. It has lower utility cost and hydrolysis occurs under mild reaction conditions. Microorganisms that degrade cellulose are abundant and universal in nature. The enzymatic hydrolysis of cellulose requires the use of cellulase enzyme. Fungi and bacteria are the main cellulase-producing microorganisms. A “twofold” benefit could be achieved through a sustainable bioconversion of biomass by cellulase enzyme. First, it would reduce the amount of cellulosic waste and diminish its effects on our environment; and second, the bioconversion of waste would be an alternative source of fuel energy to shrink our growing dependence on fossil fuels.

Preparation and properties of biodegradable polymer/nano-hydroxyapatite bioceramic scaffold for spongy bone regeneration

Abstract Biodegradable polymer/bioceramic composite scaffolds can overcome the limitations of conventional ceramic bone substitutes, such as brittleness and difficulty in shaping. To better mimic the mineral components and microstructure of natural bone, a novel nano-hydroxyapatite (nHAp)–chitosan composite scaffold including gelatin and polymer (poly(lactic acid)) with high porosity was developed using a sol-gel method and subsequently lyophilized for efficient bone tissue engineering. The nanocrystalline structure of hydroxyapatite was observed using X-ray diffraction analysis and the composite showed crystallinity due to the presence of nHAp. The pore diameter of the composite containing 5% nHAp was found to be 125 μm, while the composites with 10%, 15%, and 20% nHAp revealed a smaller pore size in the range of 15–28 μm. The highest compressive strength of 5.5 MPa was observed for the 10% nHAp-containing scaffold, whereas thermogravimetric analysis showed 90%–94% degradation at a temperature of 600°C, which demonstrated its excellent thermal stability. Antibacterial and cytotoxicity test results revealed that the composite is resistant toward microbial attack and has low sensitivity in cytotoxicity. The compressive strength data suggests that the composite does not have enough strength as that of human compact bone; however, the highly porous structure as observed in scanning electron microscopy makes it possible for use as an excellent substrate in the spongy bone of humans.

Novel alginate-di-aldehyde cross-linked gelatin/nano-hydroxyapatite bioscaffolds for soft tissue regeneration

The present study describes the fabrication of a novel alginate-di-aldehyde (ADA) cross-linked gelatin (GEL)/nano-hydroxyapatite (nHAp) bioscaffold by lyophilization process. The physico-chemical properties of the scaffolds were evaluated in order to assess its suitability for tissue engineering application. ADA was prepared from periodate oxidation of alginate which facilitate the crosslinking between free amino group of gelatin and available aldehyde group of ADA through Schiffs base formation. nHAp was synthesized from waste egg-shells by wet chemical method. The synthesized HAp was found crystalline and nanosize (~45 nm) by XRD and TEM analysis respectively. Ca to P ratio of nHAp is 1.51 as observed by EDX confirmed the suitability of the scaffold for biomedical application. The crosslinked ADA increases thermal stability of scaffolds. Water uptake and degradation ability significantly reduced with the increase of nHAp in the scaffold due to the higher stiffness contributed by nHAp. SEM analysis revealed that the pore size and porosity of the scaffolds declines with the proliferation of nHAp in the scaffolds. XRD analysis of the scaffolds shows the increase of crystallinity in the composites due to incorporation of nHAp and ADA. Cytotoxicity of the all scaffolds were examined by normal kidney epithelial cells (Vero cells) and the results confirmed the non-toxicity of the scaffolds, which proved it is extremely cytocompatible. These tunable physical properties and enhance biocompatibility of prepared scaffold offer advance application in soft tissue regeneration and could be a promising candidate for biomedical application.

Facile Preparation of Biocomposite from Prawn Shell Derived Chitosan and Kaolinite-Rich Locally Available Clay

A novel composite material was prepared from prawn shell derived chitosan (CHT) and locally available kaolinite-rich modified Bijoypur clay (MC) using a facile technique in which dilute acetic acid was used as a solvent for dissolving chitosan and composite fabrication whereas distilled water was used for preparing the clay dispersion. Bijoypur clay mainly consists of kaolinite clay mineral and it was modified with the dodecyl amine to make it organophilic. Morphology and properties of the composites (different weight ratio of MC and CHT) have been studied and compared with those of pure CHT and MC. Purification and modification of Bijoypur clay were investigated by X-ray diffraction (XRD), X-ray fluorescence (XRF), and Fourier transformed infrared spectroscopy (FTIR) analyses. The fabrication of CHT-MC composites was confirmed by FTIR analysis. Thermogravimetric analysis (TGA) and differential scanning colorimetry (DSC) were used to investigate the thermal stability of the composites. It was observed that dispersed clay improves the thermal stability and enhances the hardness of the matrix systematically with the increase of clay loading. In this study, a better insolubility in both acidic and alkaline media of the composites is also observed compared to pure chitosan.