Cyclodextrins – development and applications of these versatile oligosaccharides

. Cyclodextrins (CDs) are cyclic oligossacharides which have been known and studied for almost 130 years. This review aims to highlight the most important findings registered over this time, the physicochemical properties, preparation methods and uses of cyclodextrins, with special focus on their recently discovered applications. Due to their unique conformation, cyclodextrins are able to encapsulate a wide range of chemical entities, impacting on their solubility, bioavailability, stability, and shelf-life. Their complex formation properties together with the production from natural sources opens the door for cyclodextrins to be used in numerous and varied industries. However, the most important consumer of these versatile sugars is represented by the biomedical domain, where cyclodextrins find uses in drug formulations, delivery systems, medical textiles, implantable devices, tissue engineering, and many other connex applications. Moreover, intense research is still performed for this compounds, to develop and extend their therapeutic potential and serve as promising alternatives for treatment of severe diseases.

Analysis of structure, bioactivity and hardness of titanium incorporated bioactive glass

A series of bioactive glass composition were prepared, and the effects of TiO2 addition on the structure, bioactivity and hardness of the glasses were analyzed. This study consisted of glass characterization, simulated body fluid (SBF) trials, and hardness testing. Three glasses were formulated, where a SiO2-CaO-Na2O-P2O5 bioactive glass was used as control, with the addition of 5 and 10 wt.% TiO2 at the expense of CaO. X-ray diffraction patterns confirmed that an amorphous microstructure was obtained for all three glasses. Differential thermal analysis indicated an increase in the glass transition temperature of the glass series from 660°C to 721°C with the incorporation of TiO2. Hot stage microscopy results exhibited higher sintering and softening temperatures for TiO2 containing glasses. Each glass was then incubated in SBF for 1, 10, and 30 days. Scanning electron microscopy images confirmed that the calcium phosphate particulates were precipitated on control glass after 10 days, however, for TiO2 containing glasses, the deposition layer was only observed after 30 days. The hardness of SBF incubated samples were tested, where TiO2 containing glasses showed significantly higher hardness values at each incubation period, with 0.72 GPa for control and 1.71 GPa for the TiO2 containing glass, after 30 days of incubation.

Nano-mechanical properties of novel intermetallic coatings on 316L bioimplant material

In the present work, Nano-mechanical properties of intermetallic layer formed on 316L austenitic stainless steel have been investigated. Hot dip aluminizing technique applied on stainless steel samples for coating and composition of Al-Si alloys maintained as 8%, 10%, 12% and 14%. Nano-mechanical properties of the Intermetallic formed have been evaluated using Nano-indentation technique at room temperature and results were compared. On the basis of our observations and obtained results it is concluded that with increasing silicon percentage the thickness of the intermetallic layer increases. However, the Nano-mechanical results showed that this layer is brittle in nature. Therefore, it can be inferred that for bio-implant application the thickness of the layer needs to be at lower level as possible.

Tissue engineered vascular grafts

With the continuous increase in the prevalence of cardiovascular diseases and the limited efficiency of conventional treatments, including diet and lifestyle modifications, pharmaceutical administration, and surgical interventions, there is an equally increased need for vascular grafts for the replacement of damaged blood vessels. Currently, autologous grafts represent the gold standard. However, due to the limited availability, intensive work has been performed in the field of vascular tissue engineering. Although there are many possibilities for obtaining synthetic vascular grafts, there is still no ideal solution for vascular replacements. In this paper, the main material categories and fabrication techniques are reviewed.

A review of chitosan-, alginate-, and gelatin-based biocomposites for bone tissue engineering

Bone diseases and injuries have a major impact on the quality of life. Classical treatments for bone repair/regeneration/replacement have various disadvantages. Bone tissue engineering (BTE) received a great attention in the last years. Natural polymers are intensively studied in this field due to their properties (biocompatibility, biodegradability, abundance in nature, high processability). Unfortunately, their mechanical properties are poor, which is why synthetic polymers or ceramics are added in order to provide the optimal compressive, elastic or fatigue strength. Moreover, growth factors, vitamins, or antimicrobial substances are also added to enhance the cell behavior (attachment, proliferation, and differentiation). In this review, new scientific results regarding potential applications of chitosan-, alginate-, and gelatin based biocomposites in BTE will be provided, along with their in vitro and/or in vivo tests.

Strategies based on stem cells for tissue engineering

Cell-therapy is a new approach in medical research field. The increased number of patients, which is reported all over the world, has led to the development of innovative solutions capable of improving wound healing. Stem cells, due to their self-renewal and differentiation capacities, gradually replace the traditional medicine used in the past. Even if the risks of using stem cells exists, the promising results they can offer have led to the design of intelligent materials that can make life easier for patients. Stem cells can be classified by many criteria, but the most important are embryonic and adult stem cells. The ability of embryonic stem cells of differentiate into any type of tissue by various strategies makes them an ideal candidate in tissue engineering applications. Ethical problems must be taken into consideration, so the most used in different therapies are adult stem cells. Nowadays, the applications of stem cells are various. They can be used in order to restore the function of soft and hard tissue and to improve the healing time of a wound. Skin problems, osteogenesis, angiogenesis or fracture healing are some examples of tissue disorders that can be restored by using stem cells therapy and nanotechnology.

Nanostructures and their application in antimicrobial drug delivery system

As multiresistant and pan-resistant infections continue to emerge, and because the development of novel antimicrobial drugs is a slow process, nanotechnology offers valuable alternatives for fighting resistant bugs, mainly by improving the therapeutic effect of current antimicrobials. Antibiotic resistance is one of the greatest global health threats of the 21st century, but nanotechnology is offering new solutions to the problem. Nanostructured biomaterials, nanoparticles in particular, have unique physicochemical properties such as ultra small and controllable size, large surface area to mass ratio, high reactivity, and functionalizable structure. These properties can be applied to facilitate the administration of antimicrobial drugs, thereby overcoming some of the limitations in traditional antimicrobial therapeutics. Carbon-based nanomaterials such as fullerenes, carbon nanotubes (CNTs) (especially single-walled carbon nanotubes (SWCNTs)) and graphene oxide (GO) nanoparticles) show potent antimicrobial properties. Nanocoating and shuttle systems have shown great promise in vitro and animal models. Noble metals nanostructures, particularly silver, have attracted much attention in the fields of medicine due to their unique properties which are strongly dependent on the size and shape of metal nanomaterials. Recent development of nanocarriers, improved the drug therapy of different diseases, together with the mechanisms of microbial inhibition.

Organic-inorganic antimicrobial nanostructures for health care applications

In recent years, the drug resistant microorganisms are a serious and increasing public health problem. New strategies for controlling bacteria activity are urgently needed and nanomaterials can be a very promising approach, as the small size of the particle gives large surface area and consequently reactivity (and in many cases toxicity) increases substantially. The most tested metallic nanoparticles are silver, copper, gold, aluminum, titanium, iron, zinc, bismuth and others. Some of these metals have been coated onto several other materials. Another strategy is to incorporate these metals into a substrate such as polymethyl methacrylate forming organic-inorganic antimicrobial nanostructures. With respect to bacteria and fungi, the most frequent candidates for microbial experiments are: Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumonia, Bacillus subtilis among other species. The antimicrobial potential of these nanostructured particles, their mechanism of action and health care applications are presented and discussed at length in this review.

Nano-structured metal-semiconductor-metal photodetector for sensor network systems

The advanced and smart ways to produce complex nano-structures have incorporated new capabilities in various aspects of science and technology where structures on nano-meter scales are desirable including high-speed communication and sensor networks, and future biomedical sensors and detectors. In recent years, there has been a growing interest towards the miniaturization of optical and electrical components with faster and more efficient performance. The development of nano-materials and nano-structures design provides great opportunity for building multifunctional sensing elements which are smaller and more efficiently incorporated. Furthermore they have other useful characteristics like reduced production cost and minimized power consumption. Wireless sensor network systems have been identified as one of the most important technologies for the 21st century (Chong et. al., 2003). It can be deduced from its name that sensor network systems are composed of several sensor nodes, where each component is responsible for a function in the whole system, where it can consist of different kinds of sensors such as, thermal, visual, biomedical, infrared, acoustics, etc. Recent wireless communication system development requires a concurrent speedy advancement of sensors characteristics as well as the system performance. Therefore, it is very important to make the progress in sensors design with tiny dimensions, suitable for communication over a sensor network system with specified purposes such as, monitoring different parameters, namely humidity, temperature, light in household, cities, and different environments (Ian-Akyildiz et al., 2002). The main focus of this review is to design and model an optimized plasmonics-based metal-semiconductor-metal photodetectors (MSM-PDs) with sub-wavelength architectures that is useful for high-speed optical communication systems and sensor network systems. Nano-structures designed on top of the electrodes trigger surface plasmon polaritons (SPPs) excitation and enable routing and manipulation of the light to be eventually trapped into the device active region.

Application of nanoparticles in oral hygiene

Many of more than 700 bacterial species inhabiting the oral cavity are opportunistic pathogens causing systemic infections in addition to dental and periodontal diseases. This renders oral hygiene a much serious issue, which is further exacerbated with the emergence of multiple antibiotic resistance in oral bacteria. The role of nanoparticles based materials especially metal and metal oxide nanoparticles as an effective and alternative/supplementary antimicrobial agent is now well established. These nanoparticles could be a healthier, innocuous and effective alternative for controlling both the dental biofilms and oral planktonic bacterial population with lesser side effects or antibiotic resistance. Antimicrobial activity of these nanoparticles against a number of oral pathogens has already been demonstrated. When added to artificial dental materials and implants these nanoparticles improve the desirable physico-chemical properties of the materials in addition to improving their antimicrobial activity. Besides a few studies, biochemical processes underlying the antimicrobial activity of the nanoparticles against both planktonic cells and oral biofilms is not understood. Through our literature survey it is envisaged that ZnO nanoparticles and TiO2 nanoparticles are the most suitable nanoantibiotic for the development of dental pastes, mouthwashes, and other oral hygiene materials. However in vivo studies on nanotoxicity of these nanoparticles are missing and need a careful and balanced evaluation before successful clinical translations.