For the synthesis of hydroxyapatite crystals from aqueous solutions three preparation methods were employed. From the experimental processes and the characterization of the crystals it was concluded that aging and precipitation kinetics are critical for the purity of the product and its crystallographic characteristics. The authentication details are presented along with the results from infrared spectroscopy, X-ray powder diffraction, Raman spectroscopy, transmission and scanning electron photographs, and chemical analysis. Analytical data for several calcium phosphates were collected from the literature, extensively reviewed, and the results were grouped and presented in tables to provide comparison with the data obtained here.

The release kinetics for a variety of proteins of a wide range of molecular mass, hydrodynamic radii, and isoelectric points through a nanofiber hydrogel scaffold consisting of designer self-assembling peptides were studied by using single-molecule fluorescence correlation spectroscopy (FCS). In contrast to classical diffusion experiments, the single-molecule approach allowed for the direct determination of diffusion coefficients for lysozyme, trypsin inhibitor, BSA, and IgG both inside the hydrogel and after being released into the solution. The results of the FCS analyses and the calculated pristine in-gel diffusion coefficients were compared with the values obtained from the Stokes-Einstein equation, Fickian diffusion models, and the literature. The release kinetics suggested that protein diffusion through nanofiber hydrogels depended primarily on the size of the protein. Protein diffusivities decreased, with increasing hydrogel nanofiber density providing a means of controlling the release kinetics. Secondary and tertiary structure analyses and biological assays of the released proteins showed that encapsulation and release did not affect the protein conformation and functionality. Our results show that this biocompatible and injectable designer self-assembling peptide hydrogel system may be useful as a carrier for therapeutic proteins for sustained release applications. drug delivery ͉ protein diffusion ͉ single-molecule analysis ͉ spectroscopic analyses ͉ antibody-antigen interactions H ydrogels have long been recognized as being well suited for numerous biomedical applications, including regenerative medicine and controlled drug release (1-3). The successful implementation of these materials, however, depends on many factors, including component and degradation product toxicity, inflammatory host response, the ease of incorporating cellspecific bioactive moieties, and the controlled and sustainable release of the active compound over prolonged periods of time. Despite the intense research conducted on myriad natural and synthetic materials (i.e., polyglycolic-polylactic acid, agarose, collagen, alginate, etc.), all of these challenges have not been resolved yet for a single system (2, 4).In 1993, we discovered that a class of self-assembling peptides comprising alternating hydrophobic and hydrophilic amino acids spontaneously self-organize into interwoven nanofibers with diameters of 10-20 nm upon being introduced to electrolyte solutions (5). These nanofibers further organize to form highly hydrated hydrogels [up to Ϸ99.5% (wt/vol) water], with pore sizes between 5 and 200 nm in diameter. Peptide hydrogels not only have all of the advantages of ''traditional'' hydrogels but also do not use harmful materials (e.g., toxic cross-linkers, etc.) to initiate the solution-gel transformation (2) whereas the degradation products are natural amino acids, which can be metabolized. The fact that the solution-gel transition occurs at physiological conditions and the high internal hydration of the hydrogel allows for ...

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Until the mid-1980s, mainly biologists were conducting peptide research. This changed with discoveries that opened new paths of research involving the use of peptides in bioengineering, biotechnology, biomedicine, nanotechnology, and bioelectronics. Peptide engineering and rational design of novel peptide sequences with unique and tailormade properties further expanded the field. The discovery of short self-assembling peptides, which upon association form well-defined supramolecular architectures, created new and exciting areas of research. Depending on the amino acid sequence, the pH, and the type of the electrolyte in the medium, peptide self-assembly leads to the formation of nanofibers, which are further organized to form a hydrogel. In this review, the application of ionic complementary peptides which self-assemble to form nanofiber hydrogels for tissue engineering and regenerative medicine will be discussed through a selective presentation of the most important work performed during the last 25 years. V C 2016 Wiley Periodicals, Inc.

Current theories agree that there appears to be no unique feature responsible for the remarkable heat stability properties of hyperthermostable proteins. A concerted action of structural, dynamic and other physicochemical attributes are utilized to ensure the delicate balance between stability and functionality of proteins at high temperatures. We have thoroughly screened the literature for hyperthermostable enzymes with optimal temperatures exceeding 100 °C that can potentially be employed in multiple biotechnological and industrial applications and to substitute traditionally used, high‐cost engineered mesophilic/thermophilic enzymes that operate at lower temperatures. Furthermore, we discuss general methods of enzyme immobilization and suggest specific strategies to improve thermal stability, activity and durability of hyperthermophilic enzymes.