Se-Kwon Kim

Chitosan Composites for Bone Tissue Engineering—An Overview

Bone contains considerable amounts of minerals and proteins. Hydroxyapatite [Ca10(PO4)6(OH)2] is one of the most stable forms of calcium phosphate and it occurs in bones as major component (60 to 65%), along with other materials including collagen, chondroitin sulfate, keratin sulfate and lipids. In recent years, significant progress has been made in organ transplantation, surgical reconstruction and the use of artificial protheses to treat the loss or failure of an organ or bone tissue. Chitosan has played a major role in bone tissue engineering over the last two decades, being a natural polymer obtained from chitin, which forms a major component of crustacean exoskeleton. In recent years, considerable attention has been given to chitosan composite materials and their applications in the field of bone tissue engineering due to its minimal foreign body reactions, an intrinsic antibacterial nature, biocompatibility, biodegradability, and the ability to be molded into various geometries and forms such as porous structures, suitable for cell ingrowth and osteoconduction. The composite of chitosan including hydroxyapatite is very popular because of the biodegradability and biocompatibility in nature. Recently, grafted chitosan natural polymer with carbon nanotubes has been incorporated to increase the mechanical strength of these composites. Chitosan composites are thus emerging as potential materials for artificial bone and bone regeneration in tissue engineering. Herein, the preparation, mechanical properties, chemical interactions and in vitro activity of chitosan composites for bone tissue engineering will be discussed.

Purification and characterization of angiotensin I converting enzyme (ACE) inhibitory peptides from Alaska pollack (Theragra chalcogramma) skin

Abstract Proteolytic digestion of gelatin extracts from Alaska Pollack ( Theragra chalcogramma ) skin brings about a high angiotensin I converting enzyme (ACE) inhibitory activity. Gelatin extracts were hydrolyzed by serial protease-treatments in the order of Alcalase, pronase E, and collagenase using a three-step recycling membrane reactor. Fragments arising from the third step were composed of peptides ranging from 0.9 to 1.9 kDa and responsible for ACE inhibitory activity. Catalytically active two peptides were separated by the consecutive chromatographic methods including gel filtration, ion-exchange chromatography, and reverse-phase high performance liquid chromatography. The isolated peptides were composed of Gly-Pro-Leu and Gly-Pro-Met and showed IC 50 values of 2.6 and 17.13 μM, respectively. These results suggested that Gly-Pro-Leu would be useful as a new antihypertensive agent.

Production of chitooligosaccharides using an ultrafiltration membrane reactor and their antibacterial activity

Abstract To increase the solubility of chitosan in an aqueous solution and to facilitate its utilization, the enzymatic production of chitooligosaccharides with a high degree of polymerization (DP) was carried out using an ultrafiltration (UF) membrane reactor system. 80% of the oligosaccharides produced were in the range DP3–6. Compared with a batch reactor, in the UF membrane reactor system, at least 11 batches of substrate could be hydrolysed for the same quantity of chitosanuse. Oligosaccharides obtained using the reactor system showed antibacterial activity and a 0.5% concentration completely inhibited the growth of Escherichia coli .

Improvement of functional properties of cod frame protein hydrolysates using ultrafiltration membranes

Abstract Enzymic hydrolysis was applied for the efficient recovery of the protein sources from the fish processing by-product, cod frame. The enzyme used for the hydrolysis was crude proteinase extracted from tuna pyloric caeca. The resultant hydrolysate, cod frame protein hydrolysate (CFPH), was separated based on the molecular weight of the peptides in the hydrolysate and several functional properties were examined, including physicochemical properties (emulsifying and foaming property) and bioactivities (antioxidative and angiotensin I converting enzyme (ACE) inhibitory activity) to determine its potential functions. CFPH was processed through a series of ultrafiltration (UF) membranes with molecular weight cut-off (MWCO) of 30, 10, 5 and 3 kDA, and four types of permeates including 30-K (permeate from 30 kDA), 10-K (permeate from 10 kDA), 5-K (permeate from 5 kDA) and 3-K hydrolysate (permeate from 3 kDA) were obtained. 10- and 30-K hydrolysates showed excellent emulsion properties and whippability. The 10-K hydrolysate showed high antioxidative activity, while the 3-K hydrolysate had excellent ACE inhibitory activity. In terms of all functional properties tested, the fractionated hydrolysates were superior to the original non-separated hydrolysate. These results suggested that separating hydrolysate enhanced several functional properties.

Immense essence of excellence: marine microbial bioactive compounds.

Oceans have borne most of the biological activities on our planet. A number of biologically active compounds with varying degrees of action, such as anti-tumor, anti-cancer, anti-microtubule, anti-proliferative, cytotoxic, photo protective, as well as antibiotic and antifouling properties, have been isolated to date from marine sources. The marine environment also represents a largely unexplored source for isolation of new microbes (bacteria, fungi, actinomycetes, microalgae-cyanobacteria and diatoms) that are potent producers of bioactive secondary metabolites. Extensive research has been done to unveil the bioactive potential of marine microbes (free living and symbiotic) and the results are amazingly diverse and productive. Some of these bioactive secondary metabolites of microbial origin with strong antibacterial and antifungal activities are being intensely used as antibiotics and may be effective against infectious diseases such as HIV, conditions of multiple bacterial infections (penicillin, cephalosporines, streptomycin, and vancomycin) or neuropsychiatric sequelae. Research is also being conducted on the general aspects of biophysical and biochemical properties, chemical structures and biotechnological applications of the bioactive substances derived from marine microorganisms, and their potential use as cosmeceuticals and nutraceuticals. This review is an attempt to consolidate the latest studies and critical research in this field, and to showcase the immense competence of marine microbial flora as bioactive metabolite producers. In addition, the present review addresses some effective and novel approaches of procuring marine microbial compounds utilizing the latest screening strategies of drug discovery.

PREPARATION OF CHITIN AND CHITOSAN OLIGOMERS AND THEIR APPLICATIONS IN PHYSIOLOGICAL FUNCTIONAL FOODS

Chitin and chitosan are known to possess multiple functional properties. Chitin is insoluble in any common solvent containing organic or mineral acid as well as water. Chitosan is water-insoluble and highly viscous in dilute acidic solutions. These solubility problems may restrict their use in physiological functional foods. However, chitin and chitosan oligomers are not only water-soluble and their solutions have low viscosity values, but they may also be absorbed in the human intestine. They may have much physiological functionality in the in vivo systems. This review demonstrates that chitin and chitosan oligomers can be prepared by chemical and enzymatic hydrolyses and that the oligomers with high degrees of polymerization, especially those with six residues or more, show strong physiological activities.

Alginate composites for bone tissue engineering: A review

Bone is a complex and hierarchical tissue consisting of nano hydroxyapatite and collagen as major portion. Several attempts have been made to prepare the artificial bone so as to replace the autograft and allograft treatment. Tissue engineering is a promising approach to solve the several issues and is also useful in the construction of artificial bone with materials including polymer, ceramics, metals, cells and growth factors. Composites consisting of polymer-ceramics, best mimic the natural functions of bone. Alginate, an anionic polymer owing enormous biomedical applications, is gaining importance particularly in bone tissue engineering due to its biocompatibility and gel forming properties. Several composites such as alginate-polymer (PLGA, PEG and chitosan), alginate-protein (collagen and gelatin), alginate-ceramic, alginate-bioglass, alginate-biosilica, alginate-bone morphogenetic protein-2 and RGD peptides composite have been investigated till date. These alginate composites show enhanced biochemical significance in terms of porosity, mechanical strength, cell adhesion, biocompatibility, cell proliferation, alkaline phosphatase increase, excellent mineralization and osteogenic differentiation. Hence, alginate based composite biomaterials will be promising for bone tissue regeneration. This review will provide a broad overview of alginate preparation and its applications towards bone tissue engineering.

Biological activities and potential health benefits of bioactive peptides derived from marine organisms

Marine organisms have been recognized as rich sources of bioactive compounds with valuable nutraceutical and pharmaceutical potentials. Recently, marine bioactive peptides have gained much attention because of their numerous health beneficial effects. Notably, these peptides exhibit various biological activities such as antioxidant, anti-hypertensive, anti-human immunodeficiency virus, anti-proliferative, anticoagulant, calcium-binding, anti-obesity and anti-diabetic activities. This review mainly presents biological activities of peptides from marine organisms and emphasizing their potential applications in foods as well as pharmaceutical areas.

Pharmaceutically active secondary metabolites of marine actinobacteria.

Marine actinobacteria are one of the most efficient groups of secondary metabolite producers and are very important from an industrial point of view. Many representatives of the order Actinomycetales are prolific producers of thousands of biologically active secondary metabolites. Actinobacteria from terrestrial sources have been studied and screened since the 1950s, for many important antibiotics, anticancer, antitumor and immunosuppressive agents. However, frequent rediscovery of the same compounds from the terrestrial actinobacteria has made them less attractive for screening programs in the recent years. At the same time, actinobacteria isolated from the marine environment have currently received considerable attention due to the structural diversity and unique biological activities of their secondary metabolites. They are efficient producers of new secondary metabolites that show a range of biological activities including antibacterial, antifungal, anticancer, antitumor, cytotoxic, cytostatic, anti-inflammatory, anti-parasitic, anti-malaria, antiviral, antioxidant, anti-angiogenesis, etc. In this review, an evaluation is made on the current status of research on marine actinobacteria yielding pharmaceutically active secondary metabolites. Bioactive compounds from marine actinobacteria possess distinct chemical structures that may form the basis for synthesis of new drugs that could be used to combat resistant pathogens. With the increasing advancement in science and technology, there would be a greater demand for new bioactive compounds synthesized by actinobacteria from various marine sources in future.

Brown seaweed fucoidan: biological activity and apoptosis, growth signaling mechanism in cancer.

Seaweeds, being abundant sources of bioactive components have much interest in recent times. The complex polysaccharides from the brown, red and green seaweeds possess broad spectrum therapeutic properties. The sulfated polysaccharides are routinely used in biomedical research and have known biological activities. Fucoidan, a fucose-rich polysaccharide extracted from brown seaweed has various biological functions including anticancer effects. Cellular damage induces growth arrest and tumor suppression by inducing apoptosis, the mechanism of cell death depends on the magnitude of DNA damage following exposure to anticancer agents. Apoptosis is mainly regulated by cell growth signaling molecules. Number of research studies evidenced that fucoidan shown to induce cytotoxicity of various cancer cells, induces apoptosis, and inhibits invasion, metastasis and angiogenesis of cancer cells. There are few articles discussing on fucoidan biological activity but no specific review on cancer and its signaling mechanism. Hence, this review discusses the brown seaweed fucoidan structure and some biological function and role in apoptosis, invasion, metastasis, angiogenesis and growth signal mechanism on cancer.