Engineered knottin peptides as diagnostics,therapeutics, and drug delivery vehicles

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Molecular diagnostics as a predictive tool: genetics of drug efficacy and toxicity

There is a rapidly growing body of evidence linking genetic polymorphisms with functional changes in proteins that are responsible for the metabolism and disposition of many medications. Likewise, polymorphisms in genes encoding the targets of medications (e.g. receptors) can alter the pharmacodynamics of the drug response by changing receptor sensitivity. As a result, the inherited basis of drug effects is often polygenic in nature, and thus more challenging to define. However, technological advances, coupled with new insights into the molecular pharmacology of medications and the functional consequences of polymorphisms in the human genome, are providing the tools needed to elucidate genetic determinants of drug response, and translate functional genomics into personalized medicine.     

Liposomal drug delivery, a novel approach: PLARosomes

Almost from the time of their rediscovery in the 60's and the demonstration of their entrapment potential, liposomal vesicles have drawn attention of researchers as potential carriers of various bioactive molecules that could be used for therapeutic applications in humans and animals. Several commercial liposome-based drugs have already been discovered, registered and introduced with great success on the pharmaceutical market. However, further studies, focusing on the elaboration of more efficient and stable amphiphile-based vesicular (or non-viral) drug carriers are still under investigation. In this review we present the achievements of our group in this field. We have discovered that natural amphiphilic dihydroxyphenols and their semisynthetic derivatives are promising additives to liposomal lipid compositions. The presence of these compounds in lipid composition enhances liposomal drug encapsulation, reduces the amount of the lipid carrier necessary for efficient entrapment of anthracycline drugs by a factor of two, stabilizes liposomal formulation of the drug (both in suspension and in a lyophilized powder), does not influence liposomal fate in the blood circulation system and benefits from other biological activities of their resorcinolic lipid modifiers.     

微针技术用于非经皮途径的药物递送研究进展

近年来,微针作为一种新兴的经皮给药技术,具有微创、无痛、使用方便和高效的特点,逐渐成为一种极具研究价值和应用潜力的给药策略。微针技术在过去20年中得到迅速发展并呈现出多样化的趋势,已可根据不同需求来定制微针的形状、组成、机械性能和其他特殊功能等。由于微针能以微创方式穿越各种生物屏障,因此许多研究人员探索了微针在除皮肤外各类组织和器官中的药物递送应用。本文综述了微针技术及其近年来在眼睛、血管、心脏等组织和器官的药物递送中的应用研究,以期推动微针技术的应用发展。     

脂质体药物传递系统

脂质体已经发展成为一种成熟的传递系统,从脂质体作为载体概念的提出发展到生产制药水平历经了很长的发展阶段,如今脂质体制剂已有效地应用于重要疾病的治疗领域。简述了有关药物传递脂质体的目标和系统,透视了那些正在研究的领域,以及有哪些机会可合理改进脂质体的药物治疗。     

A kinetic method for measuring functional delivery of amphotericin B by drug delivery systems.

The human toxicity of amphotericin B can be considerably reduced by associating the drug with liposomes of varying lipid compositions. Some lipid compositions are much more effective than others. We show that a simple kinetic fluorescence assay using pyranine as an indirect probe of amphotericin-induced K+ currents may be used to study different liposomal drug delivery systems in vitro. We find that lipid mixtures composed of DMPC/DMPG/amphotericin at a 7:3:1 mole ratio show very slow functional delivery with a preference for ergosterol over cholesterol-containing membrane vesicles. On the other hand, amphotericin delivered from egg phosphatidylcholine liposomes lead to 100-fold increases in K+ leakage at one-fifth the amphotericin concentration of the 7:3:1 system. The egg phosphatidylcholine system as well as micellar amphotericin also show a slight selectivity towards cholesterol-containing vesicles over ergosterol. These results are consistent with previous clinical and in vitro cellular studies and this technique may prove valuable in screening of other delivery systems.     

Measuring Achilles tendon mechanical properties: a reliable, noninvasive method

The purpose of this technical report is to describe a cost-effective and highly reliable methodology to measure mechanical and material properties of the Achilles tendon. Subjects are positioned on an isokinetic dynamometer time synchronized to a diagnostic ultrasound device. A tendon fascicle distal to the soleus is visualized during a ramped isometric maximal plantarflexion contraction. Excursion of the fascicle and tendon torque output yield a force-elongation curve in which mechanical characteristics and material properties are derived. Excellent intrasession and intersession reliabilities were observed for both the dynamometer (intraclass correlation coefficient [ICC] 0.99, 0.95) and excursion (ICC 0.99, 0.93) measures. Practical applications for this methodology include examination of training regimes for optimal tendon adaptation and rehabilitation in the presence of tendinopathy.     

A new method for targeted drug delivery using polymeric microcapsules

Recent research and clinical evidence suggest that thalidomide could potentially be used to treat inflammation associated with Crohn's disease. However, systemic side effects associated with large doses of this drug have limited its widespread use. Treatment, with thalidomide would prove more efficacious if the drug could be delivered directly to target areas in the gut, thereby reducing systemic circulation. Microcapsule encapsulation could enable direct delivery of the drug. To assess the latter, we designed and tested drug-targeting release characteristics of alginate-poly-l-lysine-alginate (APA) microcapsules in simulated gastrointestinal environments. The results show that APA capsules enabled delivery of thalidomide in the middle and distal portions of the small intestine. We also compared the APA membrane formulation with an earlier designed alginate chitosan (AC) membrane thalidomide formulation. The results show that both APA and AC capsules allow for successful delivery of thalidomide in the gut and could prove beneficial in the treatment of Crohn's disease. However, further research is required.     

Polyketal nanoparticles: a new pH-sensitive biodegradable drug delivery vehicle

In this report, we present an acid-sensitive drug delivery vehicle, termed polyketal nanoparticles, which are designed to target therapeutics to the acidic environments of tumors, inflammatory tissues, and phagosomes. The polyketal nanoparticles are formulated from poly(1,4-phenyleneacetone dimethylene ketal) (PPADK), a new hydrophobic polymer which contains ketal linkages in its backbone. The polyketal nanoparticles undergo acid-catalyzed hydrolysis into low molecular weight hydrophilic compounds and should therefore release encapsulated therapeutics at an accelerated rate in acidic environments. Importantly, the polyketal nanoparticles do not generate acidic degradation products after hydrolysis, as with polyester-based biomaterials. Dexamethasone-loaded nanoparticles, 200-600 nm in diameter, were fabricated with PPADK via an emulsion procedure using chloroform and water. The hydrolysis half-life of PPADK was measured to be 102 h at pH 7.4 and 35 h at pH 5.0. PPADK was synthesized by a new polymerization strategy based on the acetal exchange reaction. This new delivery system should find numerous applications in the field of drug delivery because of its ease of synthesis and excellent degradation properties.     

Self-assembled surfactant nano-structures important in drug delivery: a review

Role of self assembled structures as a vehicle is significant over the years. Their applications have been found for all routes of drug delivery. These micro and nano structures are containers loaded with drugs, ideal for targeted and sustained release of the drug. Drug efficacy depends on the drug loaded into the vehicle, temperature, drug solubility, pH, release characteristics, additives and most significantly, the vehicle morphology. This in turn suggests that the same vehicle cannot be used with high efficiency for all types of drugs and locations where the drug delivery has to take place. The status of various self assembled structures and their applications in drug delivery is reviewed in this communication.     

Development of a PCR-based method for diagnostics of mycoses

Since the express-diagnostics of mycoses in immune-deficit patients still remains an acute problem, we developed an effective test system (Kan-Am) to detect DNA Candida albicans, which is a leader in the list of causative agents of candidosis. A comparison study of three PCR-systems used to detect a broad spectrum of fungoid pathogens was carried out, and a universal system (FungAm), which ensures the detection of DNAs of above 78 strains of 25 types of pathogenic fungi, was selected. The results of clinical testing of the species-specific and universal PCR-systems are well confirmed by the culture method, and they are indicative of the efficacy of applying them for the diagnostics of mycoses in neonatology. The use of the mentioned systems is a promising factor for the express-diagnostics of mycoses in immunodeficiency patients. The high sensitivity of the method makes it possible to detect 10 to 100 cells of a causative agent in 100 mcl of the examined biological material, which is compatible with the culture method. A kit of dry reagents (IonoMix) designed for an accelerated sample preparation and isolation, from them, of DNAs on the basis of Chelex-100 and of proteinase K was worked out; the kit is portable and meant for a long-term storing.     

Nanotechnology and aptamers: applications in drug delivery

Nucleic acid ligands, also known as aptamers, are a class of macromolecules that are being used in several novel nanobiomedical applications. Aptamers are characterized by high affinity and specificity for their target, a versatile selection process, ease of chemical synthesis and a small physical size, which collectively make them attractive molecules for targeting diseases or as therapeutics. These properties will enable aptamers to facilitate innovative new nanotechnologies with applications in medicine. In this review, we will highlight recent developments in using aptamers in nanotechnology solutions for treating and diagnosing disease.     

Tumour-targeted drug and gene delivery: principles and concepts

Delivery systems for tumour targeting fall into two basic categories: drug conjugate systems, in which individual drug molecules are chemically modified to target them directly to the tumour; and carrier-based systems, in which the drug or gene is first packaged non-covalently into a synthetic carrier that is then targeted to the tumour. In both cases, the objective is to maximise exposure of the target cells to the drug yet minimise side effects that result from nonspecific toxicity in normal tissues. The creation of such dose differentials is based on phenotypic differences between the tumour and the rest of the body. However, although a wide range of such changes have been linked to the transformation of normal cells to cancer cells, no single common feature exists to allow unambiguous targeting to the tumour. In addition, the tumour microenvironment creates physical barriers that significantly impair transport within the tumour. It is therefore important to match the delivery requirements of the drug to the capabilities of the delivery system. In this review, a brief overview is given of the underlying concepts and principles that help guide the development of such tumour-targeting strategies.     

Amphipathic peptides and drug delivery

The discovery of cell-penetrating peptides as gene delivery systems and the interest in the mechanism by which these vectors cross the cell membrane have generated a large number of studies. Among the parameters involved in the translocation process, controversy has arisen about the role of the amphipathicity of the carriers in the interaction and reorganization of the cell membrane. In this review we have summarized the vectors with primary or secondary amphipathicity related to secondary structure. Some of the insights into the relationship between the aggregation state of the peptide at the concentrations used for internalization studies and its interaction with the cell membrane result from our contribution to the field with a new family of amphipathic proline-rich peptides.     

Polymethyl-methacrylate-sorbitol-based capsules as local drug delivery vehicles: a preliminary study

Local delivery of antibiotics via PMMA (polymethyl-methacrylate) has been widely used in the treatment of chronic osteomyelitis for over 40 years. Unfortunately, PMMA is water insoluble, which seriously limits antibiotic delivery. In addition, the polymerization temperature of PMMA is high, and consequently, only heat-stable antibiotics can be used. Therefore our aim has been to develop an effective antibiotic delivery system, which can be loaded with a wide variety of drugs and deliver the molecules in a predictable manner. Capsules with wall thicknesses of 0.3-0.6 mm from PMMA mixtures containing 40-70 w/w% (weight percent) of sorbitol were prepared and their permeability tested with BPB (Bromophenol Blue). Sorbitol content and wall thickness correlated with the BPB release. SEM (scanning electron microscopy) showed that the canalization of capsules also was well correlated with both sorbitol content and wall thickness. The PMMA-sorbitol-based capsule can potentially be a versatile tool in assuring effective delivery of antibiotics and other substances.     

Liposomes as lubricants: beyond drug delivery

In this paper we review recent work (Goldberg et al., 2011a,b) on a new use for phosphatidylcholine liposomes: as ultra-efficient boundary lubricants at up to the highest physiological pressures. Using a surface force balance, we have measured the normal and shear interactions as a function of surface separation between layers of hydrogenated soy phophatidylcholine (HSPC) small unilamellar vesicles (SUVs) adsorbed from dispersion, at both pure water and physiologically high salt concentrations of 0.15 M NaNO(3). Cryo-Scanning Electron Microscopy shows each surface to be coated by a close-packed HSPC-SUV layer with an over-layer of liposomes on top. The shear forces reveal strikingly low friction coefficients down to 2×10(-5) in pure water system or 6×10(-4) in the 150 mM salt system, up to contact pressures of at least 12 MPa (pure water) or 6 MPa (high salt), comparable with those in the major joints. This low friction is attributed to the hydration lubrication mechanism arising from rubbing of the highly hydrated phosphocholine-headgroup layers exposed at the outer surface of each liposome, and provides support for the conjecture that phospholipids may play a significant role in biological lubrication.     

Floating drug delivery systems: A review

The purpose of writing this review on floating drug delivery systems (FDDS) was to compile the recent literature with special focus on the principal mechanism of floatation to achieve gastric retention. The recent developments of FDDS including the physiological and formulation variables affecting gastric retention, approaches to design single-unit and multiple-unit floating systems, and their classification and formulation aspects are covered in detail. This review also summarizes the in vitro techniques, in vivo studies to evaluate the performance and application of floating systems, and applications of these systems. These systems are useful to several problems encountered during the development of a pharmaceutical dosage form. Published: October 19, 2005