Hydrogel containing minocycline and zinc oxide-loaded serum albumin nanopartical for periodontitis application: preparation, characterization and evaluation.

Periodontal disease is a complex problem which often interrelates with several serious systemic diseases. However, the satisfactory clinical therapy has yet to be achieved. Herein, serum albumin microspheres containing minocycline and zinc oxide nanoparticals (ZnO NPs) were prepared and incorporated in a Carbopol 940® hydrogel. Compared with 2% minocycline ointment (Perio®), the hydrogel has shown obvious therapy effects and the ability of gingival tissue self-repairing. The serum albumin microspheres containing 0.06% of minocycline and 0.025% of ZnO NPs presented an average size of 139 ± 0.42 nm using electrophoretic light scattering (n = 3). Photomicrographs obtained by TEM showed homogeneous and spherical-shaped particles. The encapsulation efficiency was 99.99% for minocycline and the slow-release time was more than 72 h with pH-sensitive property. The in vitro skin adhesion experiment showed that the largest bioadhesive force is 0.35 N. Moreover, the hydrogel showed broad-spectrum antimicrobial and effective antibacterial ability when concentration of the ZnO NPs was over 0.2 µg/mL. The cell survival rates were more than 85% below 0.8 mg/L of ZnO NPs, which proved its low toxicity and high security.

Characterization of alkanoyl-10-O-minocyclines in micellar dispersions as potential agents for treatment of human neurodegenerative disorders.

Minocycline is a widely used antibacterial agent. Moreover, it is also demonstrated to be effective in several neurodegenerative disorders, due to its antioxidant and anti-inflammatory activities. However, the last activity is only apparent at very high doses. In fact, minocycline poorly crosses the blood-brain barrier (BBB) due to its low lipophilicity and half-life. The present work details the physicochemical characterization of a series of alkanoyl-10-O-minocycline derivatives (2-6), which are able to produce self-assembled aggregates in aqueous solution. The n-octanol/aqueous phase lipophilicity of minocycline and its derivatives were assessed by theoretical calculation, by shake-flask method, and by reversed-phase HPLC. Moreover, we determined their affinity for membrane phospholipids measuring their HPLC retention on phospholipid-based stationary phases, the so-called "Immobilized Artificial Membranes" (IAMs). Our results indicate high lipophilicity values for the minocycline derivatives (compounds 2-6); these values and the corresponding phospholipid affinities increase with the length of the hydrocarbon moiety substituent. Furthermore, the ability of the investigated alkanoyl-10-O-minocycline derivatives to self-assemble could allow a direct administration by oral and intraperitoneal routes as supramolecular systems. The advantages are an enhancement of drug solubilization, a sustained release, and the consequent less frequent drug administration. Moreover, we can hypothesize the potential solubilization in the micellar core of other poorly water soluble drugs which could improve the therapeutic effects of the pharmaceutical formulation in a combined therapy. Given the high lipophilicity of the title derivatives, they can be supposed to offer higher half-life and a better BBB penetration than minocycline. Since the new derivatives retain the structural features related to the antioxidant and anti-inflammatory effects of minocycline, they can be regarded not only as long-acting antimicrobial agents but also as candidate drugs for a targeted treatment of mental illness.

Bactericidal activity of extended 9-glycyl-amido-minocyclines.

The need for self-protecting polymer or alloy implants resistant to a broad spectrum of bacterial challenges led us to investigate covalent bonding of minocycline (MIN), a tetracycline derivative, to polystyrene beads and to titanium alloy foils by oligoethylene glycol spacers. 9-Hydrazino-acetyl-amido-MIN, and simpler glycylcycline derivatives, retained minimum inhibitory concentration (MIC) against Staphylococcus aureus comparable to MIN. However, PEG-glycyl-amido-MIN showed very low activity. Hence, we coupled 9-hydrazino-acetyl-amido-MIN to the aldehyde termini of oligoethylene glycol spacers bonded to polystyrene and titanium alloy surfaces to form acid-releasable hydrazone linkages. 9-Hydrazino-acetyl-amido-MIN was released from the monolayers more rapidly at pH 5.0 than at pH 7.4.

Synthesis and antibacterial activity of 9-substituted minocycline derivatives.

A number of 9-acylamino and 9-sulfonylamino derivatives of minocycline have been synthesized for structure-activity relationship studies. These compounds showed activity against both tetracycline-susceptible and tetracycline-resistant strains. Many of the 9-sulfonylamino derivatives exhibited improved antibacterial activity against a number of tetracycline- and minocycline-resistant Gram-positive pathogens.

The search for new antimicrobials: why we need new options.

The increasing identification of antibiotic-resistant pathogens that cause serious infections cannot be ignored. Although the future cannot be predicted with certainty, it is surely possible that an extensive epidemic of resistant bacterial infections could potentially harm millions of people. Given that it takes more than 10 years to establish the efficacy and safety of new compounds, there is an urgent need to restock the antibiotic pipeline. Only a few new antibacterial agents have received approval by the US Food and Drug Administration in the last 5 years, including linezolid in 2001, cefditoren, pivoxil and ertapenem in 2002, gemifloxacin and daptomycin in 2003, and telithromycin in 2004. Many of these agents are improved derivatives from established classes of antibiotics, and several are directed primarily at resistant Gram-positive bacteria (e.g., linezolid and daptomycin). One promising new addition is the recent approval of tigecycline (Tigacyl, Wyeth) in June 2005.

Synthesis and structure-activity relationship of novel glycylcycline derivatives leading to the discovery of GAR-936.

A number of new glycylcyclines were synthesized for structure-activity relationship study. Many of the derivatives exhibit potent, broad spectrum antibacterial activity against both tetracycline susceptible and resistant organisms. GAR-936 (TBG-MINO) shows better activity than the previously reported DMG-MINO and DMG-DMDOT.

Recent developments in tetracycline antibiotics.

The rapid emergence of pathogenic bacteria resistant to tetracyclines and other currently available antibiotics has caused serious concern among medical professionals. It has heightened resurgent interest in studying the mechanisms of resistance and in developing new antibiotics. A comprehensive review has outlined the developments of tetracyclines prior to 1980 [47]. This review will highlight the pertinent advances in the tetracycline field during the last two decades, including recent progress on elucidating the mechanisms of resistance, and the development of novel tetracyclines to combat bacterial resistance. Most of the new tetracycline derivatives described in this review have been either prepared semisynthetically or isolated from fermentation. In the semisynthetic area, efflux inhibitors that are effective in an in vitro model have been identified. A new class of tetracyclines, named glycylcyclines has been the subject of numerous reports, and will be the major focus of this review. The glycylcyclines are currently the only derivatives that exhibit antibacterial activity comparable to that of the early tetracyclines when they were first introduced. These compounds show potent activity against a broad spectrum of Gram-positive and Gram-negative bacteria, including strains that carry the two major tetracycline-resistance determinants, efflux and ribosomal protection. Two of the glycylcycline derivatives. DMG-MINO and DMG-DMDOT, have been studied by several groups of investigators against a large number of clinical pathogens isolated from various sources. The spectrum of activity of these compounds includes organisms with resistance to antibiotics other than tetracyclines, e.g., methicillin-resistant staphylococci, penicillin-resistant streptococcus pneumoniae, and vancomycin-resistant enterococci. Their in vitro, as well as in vivo activity against bacteria with characterized tetracycline- or minocycline-resistant elements will be summarized. The structure-activity relationships of glycylcyclines and their mode of action will also be discussed.