Hydrogels for biomedical applications

This article reviews the composition and synthesis of hydrogels, the character of their absorbed water, and permeation of solutes within their swollen matrices. The most important properties of hydrogels relevant to their biomedical applications are also identified, especially for use of hydrogels as drug and cell carriers, and as tissue engineering matrices.     

Hydrogels for pharmaceutical and biomedical applications

Hydrogels are crosslinked hydrophilic polymer structures that can imbibe large amounts of water or biological fluids. Hydrogels are one of the upcoming classes of polymer-based systems that embrace numerous biomedical and pharmaceutical applications. This review discusses various parameters of hydrogels such as surface properties, water content and swelling behavior, effect of nature of polymer, ionic content, and thermodynamics, all of which can influence the biomedical usage of hydrogels. Meanwhile, intelligent or environment-sensitive hydrogels and bioadhesive hydrogels continue to be important materials for medical applications; therefore, a part of this review is devoted to some of their important classes. Hydrogels are extensively used for various biomedical applications--tissue engineering, molecular imprinting, wound dressings materials, immunoisolation, drug delivery, etc. Thus, this review aims to throw light on the numerous applications that hydrogels have in the biomedical arena.     

Microbial production and biomedical applications of lovastatin

Lovastatin is a potent hypercholesterolemic drug used for lowering blood cholesterol. Lovastatin acts by competitively inhibiting the enzyme, 3-hydroxy-3-methylglutaryl coenzyme A reductase involved in the biosynthesis of cholesterol. Commercially lovastatin is produced by a variety of filamentous fungi including Penicillium species, Monascus ruber and Aspergillus terreus as a secondary metabolite. Production of lovastatin by fermentation decreases the production cost compared to costs of chemical synthesis. In recent years, lovastatin has also been reported as a potential therapeutic agent for the treatment of various types of tumors and also play a tremendous role in the regulation of the inflammatory and immune response, coagulation process, bone turnover, neovascularization, vascular tone, and arterial pressure. This review deals with the structure, biosynthesis, various modes of fermentation and applications of lovastatin.     

Photoresponsive hydrogels for biomedical applications

Hydrogels are soft materials composed of a three-dimensional network which contain a high percentage of water similar to body tissue and are therefore regarded as a biocompatible material. Hydrogels have various potential applications in the biomedical field such as drug delivery and as scaffold for tissue engineering. Control over the physical properties of a hydrogel by an external stimulus is highly desirable and is therefore actively studied. Light is a particularly interesting stimulus to manipulate the properties of a hydrogel as it is a remote stimulus that can be controlled spatially and temporally with great ease and convenience. Therefore in recent years photoresponsive hydrogels have been investigated as an emerging biomaterial. Here we will review recent developments and discuss these new materials, and their applications in the biomedical field.     

Aptamer-based biosensors: biomedical applications

This chapter considers the use of aptamer-based biosensors (generally termed 'aptasensors') in various biomedical applications. A comparison of antibodies and aptamers is made with respect to their use in the development of biosensors. A brief introduction to biosensor design and theory is provided to illustrate the principles of the field. Various transduction approaches, viz. optical, fluorescence, acoustic wave and electrochemical, are discussed. Specific biomedical applications described include RNA folding, high-throughput screening of drugs, use as receptors for measuring biological concentrations, detection of platelet-derived growth factor, protein binding and detection of HIV-1 Tat protein.     

Silica-based nanoparticles for biomedical applications

In this short review we highlight novel uses of silica-based nanoparticles (NPs) in the biomedical sector. Silica NPs are widely used in nanotechnology because they are easy to prepare and inexpensive to produce. Their specific surface characteristics, porosity and capacity for functionalization make them good tools for biomolecule detection and separation, providing solid media for drug delivery systems and acting as contrast agent protectors. In addition, they are used as safety and biocompatible pharmaceutical additives. Here, we focus on novel techniques based on silica NPs for the most important biomedical applications.     

Stimulus-responsive liposomes for biomedical applications

Liposomes are amphipathic lipidic supramolecular aggregates that are able to encapsulate and carry molecules of both hydrophilic and hydrophobic nature. They have been widely used as in vivo drug delivery systems for some time because they offer features such as synthetic flexibility, biodegradability, biocompatibility, low immunogenicity, and negligible toxicity. In recent years, the chemical modification of liposomes has paved the way to the development of smart liposome-based drug delivery systems, which are characterized by even more tunable and disease-directed features. In this review, we highlight the different types of chemical modification introduced to date, with a particular focus on internal stimuli-responsive liposomes and prodrug activation.     

Microbial exo-polysaccharides for biomedical applications

The productions and applications of various microbial exopolysaccharides have been under intensive researches over the past few decades. Some of these exopolysaccharides are commercial available and some are currently under intensive development; they include ionic heteropolysaccharide and neutral homopolysaccharide. These extracellular polymers constitute a structurally diverse class of biological macromolecules with a wide range of physiochemical properties which are the basis for the different applications in the broad fields of pharmacy and medicine. They have found applications in such diverse biomedical fields as ophthalmology, orthopedic surgery, tissue engineering, implantation of medical devices and artificial organs, prostheses, dentistry, bone repair and drug delivery.     

Hydrogels for biomedical applications.

This article reviews the composition and synthesis of hydrogels, the character of their absorbed water, and permeation of solutes within their swollen matrices. The most important properties of hydrogels relevant to their biomedical applications are also identified, especially for use of hydrogels as drug and cell carriers, and as tissue engineering matrices.     

Glycopeptide dendrimers for biomedical applications

Combinatorial libraries of peptide dendrimers bearing two and four copies of C-fucosyl residues were screened for binding to fucose specific lectins leading to potent ligands for Ulex europaeus lectin UEA-I (IC(50) = 11 microM). The dendrimers also show high affinity for the lectin PA-IIL (IC(50) = 0.14 microM) from the pathogenic bacteria Pseudomonas aeruginosa. The dendrimers described are the first multivalent ligands for these lectins. In our system, glycopeptide dendrimer-protein binding is modulated by the nature of the amino acid residues present in the dendritic structure instead of depending solely on the number of sugars attached to the scaffold. Studies of colchicine-glycopeptide dendrimer conjugates with improved selectivity for cancer cells in comparison to colchicine are also described.     

Smart nanotubes for biomedical and biotechnological applications

Nanoparticles are being developed for a host of biomedical and biotechnological applications including drug delivery, enzyme immobilization and DNA transfection. Spherical nanoparticles are typically used for such applications, but this only reflects the fact that spheres are easier to make than other shapes. Micro- and nanotubes--structures that resemble tiny drinking straws--are alternatives and may offer advantages over spherical nanoparticles for some applications. This article discusses four different approaches to making micro- and nanotubes and reviews the current status of efforts to develop biomedical and biotechnological applications of these tubular structures.     

Alginate and alginate composites for biomedical applications

Alginate is an edible heteropolysaccharide that abundantly available in the brown seaweed and the capsule of bacteria such as Azotobacter sp. and Pseudomonas sp. Owing to alginate gel forming capability, it is widely used in food, textile and paper industries; and to a lesser extent in biomedical applications as biomaterial to promote wound healing and tissue regeneration. This is evident from the rising use of alginate-based dressing for heavily exuding wound and their mass availability in the market nowadays. However, alginate also has limitation. When in contact with physiological environment, alginate could gelate into softer structure, consequently limits its potential in the soft tissue regeneration and becomes inappropriate for the usage related to load bearing body parts. To cater this problem, wide range of materials have been added to alginate structure, producing sturdy composite materials. For instance, the incorporation of adhesive peptide and natural polymer or synthetic polymer to alginate moieties creates an improved composite material, which not only possesses better mechanical properties compared to native alginate, but also grants additional healing capability and promote better tissue regeneration. In addition, drug release kinetic and cell viability can be further improved when alginate composite is used as encapsulating agent. In this review, preparation of alginate and alginate composite in various forms (fibre, bead, hydrogel, and 3D-printed matrices) used for biomedical application is described first, followed by the discussion of latest trend related to alginate composite utilization in wound dressing, drug delivery, and tissue engineering applications.     

Gold nanostars-diagnosis,bioimaging and biomedical applications

Abstract

Gold Nanostars (GNS) have attracted tremendous attention toward themselves owing to their multi-branched structure and unique properties. These state of the art metallic nanoparticles possess intrinsic features like remarkable optical properties and exceptional physiochemical activities. These star-shaped gold nanoparticles can predominantly be utilized in biosensing, photothermal therapy, imaging, surface-enhanced Raman spectroscopy and target drug delivery applications due to their low toxicity and extraordinary optical features. In the current review, recent approaches in the matter of GNS in case of diagnosis, bioimaging and biomedical applications were summarized and reported. In this regard, first an overview about the structure and general properties of GNS were reported and thence detailed information regarding the diagnostic, bioimaging, photothermal therapy, and drug delivery applications of such novel nanomaterials were presented in detail. Summarized information clearly highlighting the superior capability of GNS as potential multi-functional materials for biomedical applications.     

Cyclodextrin-based nanogels for pharmaceutical and biomedical applications

Hydrophilic nanogels combine the advantages of hydrogels with certain advantages that are inherent in their nanoscale size. Similar to macrogels, nanogels can contain and protect drugs and regulate their release by incorporating high-affinity functional groups, stimuli-responsive conformations and biodegradable bonds into the polymer network. Similar to nanoparticles, nanogels can easily be administered in liquid form for parenteral drug delivery. The nanoscale size of nanogels gives them a high specific surface area that is available for further bioconjugation of active targeting agents. Biodistribution and drug release can be modulated through size adjustments. The incorporation of hydrophilic cyclodextrin (CD) moieties into the polymeric network of the nanogels provides them with a drug loading and release mechanism that is based on the formation of inclusion complexes without decreasing the hydrophilicity of the network. The covalent attachment of CD molecules to the chemically crosslinked networks may enable the CDs to display fully their ability to form complexes, while simultaneously preventing drug release upon media dilution. The preparation, characterization and advantages for pharmaceutical and biomedical applications of CD-based nanogels are reviewed in this article.     

Recent development and biomedical applications of self-healing hydrogels

Introduction: Hydrogels are of special importance, owing to their high-water content and various applications in biomedical and bio-engineering research. Self-healing properties is a common phenomenon in living organisms. Their endowed property of being able to self-repair after physical/chemical/mechanical damage to fully or partially its original properties demonstrates their prospective therapeutic applications. Due to complicated preparation and selection of suitable materials, the application of many host–guest supramolecular polymeric hydrogels are so limited. Thus, the design and construction of self-repairing material are highly desirable for effectively increase in the lifetime of a functional material. However, recent advances in the field of materials science and bioengineering and nanotechnology have led to the design of biologically relevant self-healing hydrogels for therapeutic applications. This review focuses on the recent development of self-healing hydrogels for biomedical application.

Areas covered: The strategies of making self-healing hydrogels and their healing mechanisms are discussed. The significance of self-healing hydrogel for biomedical application is also highlighted in areas such as 3D/4D printing, cell/drug delivery, as well as soft actuators.

Expert opinion: Materials that have the ability to self-repair damage and regain the desired mechanical properties, have been found to be excellent candidate materials for a range of biomedical uses especially if their unique characteristics are similar to that of soft-tissues. Self-healing hydrogels have been synthesized and shown to exhibit similar characteristics as human tissues, however, significant improvement is required in the fabrication process from inexpensive and nontoxic/non-hazardous materials and techniques, and, in addition, further fine-tuning of the self-healing properties are needed for specific biomedical uses.     

Nanotechnology for delivery of drugs and biomedical applications

Nanotechnology is a multidisciplinary scientific field that deals with the formulation, preparation, characterization and application of structures, devices and systems at nanometric scale. Area of concern is interdisciplinary, but with peculiarities, among others, medicine, pharmacy, biophysics, electronics, bioengineering, and molecular biology. Interest for modern nanotechnology lies in the creation and use of structures which have new properties because of their small size as well as the possibility of using these systems to control or manipulate biological structures at nanometric or atomic level. It will open the way to diagnosis and medical treatment to molecular level. This paper covers various fundamental and applied aspects of nanotechnology, in its chapters: introduction; nanoparticles (therapeutic polymers, polymeric nanoparticles, non-polymeric nanoparticles, liposomes, nanodevices) nanopharmaceutical systems used in diagnosis and therapy, in tissue engineering; pharmacokinetics and toxicity of nanoparticulate systems. Nanoparticulate systems have the potential to constitute a new generation of drug delivery systems. By their nature, nanodevices can be used as innovative diagnostic tool for detecting and monitoring disease, also for its treatment and use in developing new drugs.     

Novel pharmaceutical and biomedical applications of plasma techniques

The plasma-induced surface radicals formed on a variety of organic polymers have been studied in detail using electron-spin resonance (ESR) coupled with systematic computer simulations. On the basis of the findings from such studies on the nature of radical formation and radical reactivity, we were able to open up several novel pharmaceutical and biomedical applications in plasma treatment. In this review, applications using plasma-irradiated organic polymers are described, which include: 1) preparation of double-compressed tablets applicable for reservoir-type drug-delivery systems (DDS) for sustained and delayed release, intragastric floating DDS (FDDS) for oral controlled-release dosage forms with gastric retention capabilities, and fabrication of functionalized composite powders applicable for controlled drug release with the mechanical application of plasma-irradiated polymer powder; 2) an approach to "patient-tailored DDS," administered by taking into account that the environment (pH, transit time, etc.) in the gastrointestinal tract varies with each patient, based on the combination of the above-mentioned DDS devices; 3) plasma-assisted promotion of seed germination of herbal medicines with hard coats; and 4) fabrication of polymer surfaces with durable hydrophilicity and lubricity using plasma techniques and the immobilization of oligo-nucleotides on hydrophilic polymer surfaces thus prepared applicable to constructing DNA diagnosis systems.     

Stimuli-responsive magnetic particles for biomedical applications

In recent years, magnetic nanoparticles have been studied due to their potential applications as magnetic carriers in biomedical area. These materials have been increasingly exploited as efficient delivery vectors, leading to opportunities of use as magnetic resonance imaging (MRI) agents, mediators of hyperthermia cancer treatment and in targeted therapies. Much attention has been also focused on "smart" polymers, which are able to respond to environmental changes, such as changes in the temperature and pH. In this context, this article reviews the state-of-the art in stimuli-responsive magnetic systems for biomedical applications. The paper describes different types of stimuli-sensitive systems, mainly temperature- and pH sensitive polymers, the combination of this characteristic with magnetic properties and, finally, it gives an account of their preparation methods. The article also discusses the main in vivo biomedical applications of such materials. A survey of the recent literature on various stimuli-responsive magnetic gels in biomedical applications is also included.     

Quantum dot-based nanocomposites for biomedical applications

Quantum dot (QD) has been extensively investigated as a nanoprobe to replace conventional organic dyes due to its unique optical properties. However, nanotoxicity of QD greatly hampers its biomedical applications, particularly in in vivo imaging. It is critical to functionalize QD and/or composite QD with other functional materials for biocompatibility, multifunction and expanded applications. In this review, advances of QD-based nanocomposites are addressed with emphasis of their synthesis, fundamental understanding and applications in biosensor, multimodal imaging, drug delivery, diagnostics and cancer therapy. Some specific QD-based bionanosystems and future development directions are also discussed.     

Tailoring small proteins towards biomedical applications

Over the last two decades proteins have become increasingly important in human therapy and diagnosis. Engineering therapeutic proteins through improving their biological activity and stability has been a major interest in our group. In this mini-review we summarize our research on three proteins with pharmaceutical potential - serine protease inhibitor from squash seeds (CMTI), bovine pancreatic trypsin inhibitor (BPTI), and human fibroblast growth factor 1 (FGF1). To improve the functional properties of these proteins we used multiple techniques such as homology approach, rational design, total chemical synthesis, site-directed mutagenesis and phage display. The physicochemical properties of the obtained protein variants were evaluated using protein crystallography, spectroscopic techniques, enzymatic assays, stability measurements as well as numerous biological tests.