Showing papers in "Expert Opinion on Drug Delivery in 2011"
TL;DR: The immune recognition of nanoparticles can seriously affect the drug delivery efficacy and toxicity, and there is at present not enough knowledge on the mechanisms that dictate the nanoparticle immune recognition and stability in the biological milieu.
Abstract: Introduction: Intravenously injected nanoparticles, like any other foreign pathogen that enters the body, encounter multiple lines of defense intended to neutralize and eliminate the invading substance. Adsorption of plasma proteins on the nanoparticle surface is the first barrier of defense, which could lead to physical changes in the formulation, such as aggregation and charge neutralization, biochemical activation of defense cascades, and trigger elimination by multiple types of phagocytic cell. Areas covered: In this review, recent knowledge on the mechanisms that govern the interactions of nanoparticles (micelles, liposomes, polymeric and inorganic nanoparticles) with plasma proteins is discussed. In particular, the role of the nanoparticle surface properties and protective polymer coating in these interactions is described. The mechanisms of protein adsorption on different nanoparticles are analyzed and the implications on the clearance, toxicity and efficacy of drug delivery are discussed. The revi...
319 citations
TL;DR: The magnitude of variants of ODF technology and the advantages over conventional dosage forms promise more applications and more marketed products with ODFs in the near future.
Abstract: Introduction: Orodispersible films for oral delivery are gaining popularity. Whereas breath-fresheners and over-the-counter products have already become quite common in the US, the first prescription drug films were introduced into the EU and US markets only very recently. Already considered as a unique Rx (prescription drug) dosage form by the FDA (oral soluble film), such products are not substitutable by conventional oral dosage forms. The official term defined by the European Medicines Agency is orodispersible film (ODF). Areas covered: This review gives an overview on the benefits of ODFs, typical excipients and products already available on the market. ODFs are defined and differentiated from other films and dosage forms. Possible manufacturing methods are described. As ODFs are not yet listed in one of the pharmacopoeias, possible methods for characterization and quality control are discussed. Required characteristics, advantages and disadvantages are elaborated. Biopharmaceutical considerations ar...
277 citations
TL;DR: How immunocytes laden with drugs can cross the blood–brain or blood–tumor barriers to facilitate treatments for infectious diseases, injury, cancer, or inflammatory diseases is reviewed.
Abstract: Introduction: Drug targeting to sites of tissue injury, tumor or infection with limited toxicity is the goal for successful pharmaceutics. Immunocytes (including mononuclear phagocytes (dendritic cells, monocytes and macrophages), neutrophils and lymphocytes) are highly mobile; they can migrate across impermeable barriers and release their drug cargo at sites of infection or tissue injury. Thus, immune cells can be exploited as Trojan horses for drug delivery. Areas covered: This paper reviews how immunocytes laden with drugs can cross the blood–brain or blood–tumor barriers to facilitate treatments for infectious diseases, injury, cancer, or inflammatory diseases. The promises and perils of cell-mediated drug delivery are reviewed, with examples of how immunocytes can be harnessed to improve therapeutic end points. Expert opinion: Using cells as delivery vehicles enables targeted drug transport and prolonged circulation times, along with reductions in cell and tissue toxicities. Such systems for drug car...
270 citations
TL;DR: This review provides an overview of silk biomaterials for drug delivery, especially those that can function as long-term depots and specific examples of implantable silk drug delivery systems and injectable systems from the 1990s and onwards are reviewed.
Abstract: Introduction: Given the benefits of polymer drug delivery implants over traditional periodic systemic administration, the development of biomaterial systems with the necessary properties (biocompatibility, degradation, stabilization, controllability) is paramount. Silk fibroin represents a promising, naturally derived polymer for local, controlled, sustained drug release from fully degrading implants and the polymer can be processed into a broad array of material formats. Areas covered: This review provides an overview of silk biomaterials for drug delivery, especially those that can function as long-term depots. Fundamentals of structure and assembly, processing options, control points and specific examples of implantable silk drug delivery systems (sponges, films) and injectable systems (microspheres, hydrogels) from the 1990s and onwards are reviewed. Expert opinion: Owing to its unique material properties, stabilization effects and tight controllability, silk fibroin is a promising biomaterial for imp...
251 citations
TL;DR: There is no single universal encapsulation method that offers stable encapsulation of most drugs; each drug requires a different approach to manage all of its properties and now is the time to combine all these strategies to achieve the goal of a complex, but successful, anticancer therapy.
Abstract: Introduction: The use of liposomes increases the therapeutic index of many drugs, and also offers drug targeting and controlled release. The commercial impact of liposomes is strengthened by the invention of several active drug encapsulation methods, allowing the encapsulation of several weak base or weak acid drugs with very high drug-to-lipid ratios. Areas covered: In recent years, there have been reports on several new approaches to retain more hydrophobic drugs inside liposomes, in the circulation. Most of these methods apply drug precipitation inside preformed liposomes, as low soluble complexes with ions or chemicals. In some cases, drug derivatization was applied to enable active encapsulation of hydrophobic drugs, previously not reported to encapsulate, by active or remote loading. This review presents and compares most of the existing methods of active drug encapsulation and outlines recent strategies to achieve stable drug encapsulation in vivo. Expert opinion: At present, there is no single uni...
235 citations
TL;DR: The protective effect of SLNs, coupled with their sustained/controlled release properties, prevents drugs/macromolecules from premature degradation and improves their stability in the GIT, and make SLNs a potential BA enhancer vehicle for various Class II, III and IV drugs.
Abstract: Introduction: The therapeutic efficacy of perorally administered drugs is often obscured by their poor oral bioavailability (BA) and low metabolic stability in the gastrointestinal tract (GIT). Solid lipid nanoparticles (SLNs) have emerged as potential BA enhancer vehicles for various Class II, III and IV drug molecules. Area covered: This review examines the recent advancements in SLN technology, with regards to oral drug delivery. The discussion critically examines the effect of various key constituents on SLN absorption and their applications in oral drug delivery. The relationship between the complexity of absorption (and various factors involved during absorption, including particle size), stability and the self-emulsifying ability of the lipids used has been explored. Expert opinion: The protective effect of SLNs, coupled with their sustained/controlled release properties, prevents drugs/macromolecules from premature degradation and improves their stability in the GIT. An extensive literature survey...
226 citations
TL;DR: Today, the pharmaceutical industry has at its disposal a series of reliable and scalable formulation strategies for poorly soluble drugs, but due to a lack of understanding of the basic physical chemistry behind these strategies, formulation development is still driven by trial and error.
Abstract: Introduction: In the past two decades, there has been a spiraling increase in the complexity and specificity of drug–receptor targets. It is possible to design drugs for these diverse targets with advances in combinatorial chemistry and high throughput screening. Unfortunately, but not entirely unexpectedly, these advances have been accompanied by an increase in the structural complexity and a decrease in the solubility of the active pharmaceutical ingredient. Therefore, the importance of formulation strategies to improve the solubility of poorly water-soluble drugs is inevitable, thus making it crucial to understand and explore the recent trends. Areas covered: Drug delivery systems (DDS), such as solid dispersions, soluble complexes, self-emulsifying drug delivery systems (SEDDS), nanocrystals and mesoporous inorganic carriers, are discussed briefly in this review, along with examples of marketed products. This article provides the reader with a concise overview of currently relevant formulation strateg...
188 citations
TL;DR: Pectin-based controlled release systems, gastro-retentive systems and mucoadhesive systems present promising approaches for increasing the bioavailability of drugs, but are in their infancy.
Abstract: Introduction: Biopolymers have been used extensively in the pharmaceutical field. Pectin, a biopolymer, has several unique properties that enable it to be used as an excipient or carrier for oral d...
184 citations
TL;DR: This review covers literature which states that the dissolution enhancement of SDs is based on the fact that drugs in the nanoscale range, or in amorphous phase, dissolve faster and to a greater extent than micronized drug particles, which is in accordance to the Noyes–Whitney equation.
Abstract: Introduction: In recent years, the number of active pharmaceutical ingredients with high therapeutic impact, but very low water solubility, has increased significantly. Thus, a great challenge for pharmaceutical technology is to create new formulations and efficient drug-delivery systems to overcome these dissolution problems. Areas covered: Drug formulation in solid dispersions (SDs) is one of the most commonly used techniques for the dissolution rate enhancement of poorly water-soluble drugs. Generally, SDs can be defined as a dispersion of active ingredients in molecular, amorphous and/or microcrystalline forms into an inert carrier. This review covers literature which states that the dissolution enhancement of SDs is based on the fact that drugs in the nanoscale range, or in amorphous phase, dissolve faster and to a greater extent than micronized drug particles. This is in accordance to the Noyes–Whitney equation, while the wetting properties of the used polymer may also play an important role. Expert...
173 citations
TL;DR: This paper reviews liposomal adjuvants now in vaccine development, with particular emphasis on their adjuvant mechanism and how specific physicochemical characteristics of liposomes affect the immune response.
Abstract: INTRODUCTION: Liposomes remain at the forefront of drug and vaccine design owing to their well-documented abilities to act as delivery vehicles. Nevertheless, the concept of liposomes as delivery vehicles is not a new one, with most works focusing on their use for the delivery of genes and drugs. However, in the last 10 years a significant amount of research has focused on using liposomes as vaccine adjuvants, not only as an antigen delivery vehicle but also as a tool to increase the immunogenicity of peptide and protein antigens. AREAS COVERED: This paper reviews liposomal adjuvants now in vaccine development, with particular emphasis on their adjuvant mechanism and how specific physicochemical characteristics of liposomes affect the immune response. The inclusion of immunomodulators is also discussed, with prominence given to Toll-like receptor ligands. EXPERT OPINION: The use of liposomes as vaccine delivery systems is evolving rapidly owing to the combined increase in technological advances and understanding of the immune system. Liposomes that contain and deliver immunostimulators and antigens are now being developed to target diseases that require stimulation of both humoral and cell-mediated immune responses. The CAF liposomal system, described in detail in this review, is one liposomal model that shows such flexibility.
138 citations
TL;DR: This review article describes the principles of DoE and QbD as applicable to drug delivery development using a more apt expression, that is, ‘formulation by design (FbD)’.
Abstract: Introduction: Over the past few decades, the domain of drug formulations has metamorphosed from the conventional tablets and capsules to advanced and intricate drug delivery systems (DDS), both temporal and spatial. Formulation development of the oral DDS, accordingly, cannot be adequately accomplished using the traditional ‘trial and error’ approaches of one variable at a time. This calls for the adoption of rational, systematized, efficient and cost-efficient strategies using ‘design of experiments (DoE)’. The recent regulatory guidelines issued by the key federal agencies to practice ‘quality by design (QbD)’ paradigms have coerced researchers in industrial milieu, in particular, to use experimental designs during drug product development. Areas covered: This review article describes these principles of DoE and QbD as applicable to drug delivery development using a more apt expression, that is, ‘formulation by design (FbD)’. The manuscript describes the overall FbD methodology along with a summary of v...
TL;DR: Recent advances in the use of external stimuli to modulate drug release, as well as the synthetic strategies devoted to increase the water compatibility of these systems, which is a base requirement for their application in biomedicine.
Abstract: Introduction: Molecularly imprinted polymers (MIPs) are synthetic receptors, characterized by a high selectivity for the selected template. Among the different applications of MIPs, their use as controlled/sustained drug delivery devices has been extensively explored, even though the optimization of such devices needs to be performed before they are applied in clinical practice. Areas covered: Within drug delivery, one of the most promising fields is the possibility to modulate the drug release profile in response to a specific external stimulus; MIPs represent potentially suitable vehicles, because of the possibility to insert a stimuli-responsive co-monomer in their structure. This review discusses recent advances in the use of external stimuli to modulate drug release, as well as the synthetic strategies devoted to increase the water compatibility of these systems, which is a base requirement for their application in biomedicine. Expert opinion: Although it is easy to imagine imprinted polymers for bio...
TL;DR: This review covers current developments in parenteral and oral delivery technologies and products for poorly water-soluble compounds, such as nano-suspensions, solid dispersions and liposomes, and the use of biorelevant dissolution media to assess dissolution and solubility properties.
Abstract: Introduction: For poorly soluble compounds, a good bioavailability is typically needed to assess the therapeutic index and the suitability of the compound for technical development. In industry, the selection of the delivery technology is not only driven by technical targets, but also by constraints, such as production costs, time required for development and the intellectual property situation. Areas covered: This review covers current developments in parenteral and oral delivery technologies and products for poorly water-soluble compounds, such as nano-suspensions, solid dispersions and liposomes. In addition, the use of biorelevant dissolution media to assess dissolution and solubility properties is described. Suggestions are also included to systematically address development hurdles typical of poorly water-soluble compounds intended for parenteral or oral administration. Expert opinion: A holistic assessment is recommended to select the appropriate delivery technology by taking into account technical...
TL;DR: This article summarizes the basic concepts of mucoadhesion at the nanoscale, different techniques used for measuring the muco adhesion potential of nanosystems and strategies for increasing/decreasing mucocoadhesive interactions.
Abstract: Introduction: The benefits of mucoadhesive systems are related to the increased in situ residence and intimate contact of the delivery vehicle with the mucosa. The recent emergence of nanomedicine and the properties of nanoparticulate systems have created new challenges in understanding the nature and mechanisms of nanoscale mucoadhesion and in the development of methodologies for measuring its mucoadhesive potential. Even when usually regarded as an advantageous property, mucoadhesion can be an inconvenience for nanosystems, and strategies have been developed for minimizing interactions with the mucosal tissues/fluids. Areas covered: This article summarizes the basic concepts of mucoadhesion at the nanoscale, different techniques used for measuring the mucoadhesive potential of nanosystems and strategies for increasing/decreasing mucoadhesive interactions. Expert opinion: The mucoadhesion behavior of materials in bulk and at the nanoscale can significantly differ. Advances in the methodology used for stu...
TL;DR: New delivery systems are presented as valid alternatives to circumvent the limitations of the physicochemical characteristics and pharmacokinetics of RSV and compared with classical formulations with regard to improving RSV protection and bioavailability.
Abstract: Introduction: Resveratrol (RSV) has been one of the most extensively studied polyphenols in the last 10 years, owing to its numerous and potent therapeutic activities, namely its high antioxidant p...
TL;DR: Thermosensitive hydrogels that can serve as drug carriers and strategies used to control hydrogel properties, in order to tailor drug release kinetics, are reviewed.
Abstract: Introduction: Controlled drug delivery has been widely applied in areas such as cancer therapy and tissue regeneration. Thermosensitive hydrogel-based drug delivery systems have increasingly attracted the attention of the drug delivery community, as the drugs can be readily encapsulated and released by the hydrogels. Areas covered: Thermosensitive hydrogels that can serve as drug carriers are discussed in this paper. Strategies used to control hydrogel properties, in order to tailor drug release kinetics, are also reviewed. This paper also introduces applications of the thermosensitive hydrogel-based drug delivery systems in cancer therapy and tissue regeneration. Expert opinion: When designing a drug delivery system using thermosensitive hydrogels, one needs to consider what type of thermosensitive hydrogel needs to be used, and how to manipulate its properties to meet the desired drug release kinetics. For material selection, both naturally derived and synthetic thermosensitive polymers can be used. Var...
TL;DR: This paper reviews the current state of research and understanding of the design, characterization and performance of LNAs and discusses the opportunities and challenges associated with combining the two in a single assembly to achieve controlled release via light or radiofrequency stimuli.
Abstract: Introduction: Nanoscale assemblies are needed that achieve multiple therapeutic objectives, including cellular targeting, imaging, diagnostics and drug delivery. These must exhibit high stability, bioavailability and biocompatibility, while maintaining or enhancing the inherent activity of the therapeutic cargo. Liposome-nanoparticle assemblies (LNAs) combine the demonstrated potential of liposome-based therapies, with functional nanoparticles. Specifically, LNAs can be used to concentrate and shield the nanoparticles and, in turn, stimuli-responsive nanoparticles that respond to external fields can be used to control liposomal release. The ability to design LNAs via nanoparticle encapsulation, decoration or bilayer-embedment offers a range of configurations with different structures and functions. Areas covered: This paper reviews the current state of research and understanding of the design, characterization and performance of LNAs. A brief overview is provided on liposomes and nanoparticles for therape...
TL;DR: The key to the successful design and preparation of optimal liposomal dry powder formulations is an understanding of the significance of the drying process parameters, and the mechanisms responsible for the stabilization of liposomes during drying and in the dry state.
Abstract: Introduction: During the past 40 years, liposomes have been investigated intensively as drug carriers for anticancer drugs and as the adjuvant components of vaccines, for example. In this context, the development of dry formulations of liposomes is important to ensure a more stable drug product and to avoid the use of the ‘cold chain’ during distribution. Areas covered: This review provides an overview of the technologies commonly used for the drying of liposomal formulations and the significance of formulation and processing parameters for the drying process. In addition, a review is provided of the protective mechanisms proposed to be responsible for stabilization during processing and in the dry state, with special emphasis on the techniques used for the characterization of the mechanisms. Parameters are discussed that critically influence the liposomal stability during drying and the underlying stabilization mechanisms, including the water replacement theory, vitrification and kosmotropic effects. Exp...
TL;DR: The most important issues that need to be focused on include encapsulation efficiency, formulation stability of siRNA, degradation in circulation, endosomal escape and delivery efficiency, targeting, toxicity and off-target effects.
Abstract: Introduction: The field of RNA interference technology has been researched extensively in recent years. However, the development of clinically suitable, safe and effective drug delivery vehicles is still required. Areas covered: This paper reviews the recent advances of non-viral delivery of small interfering RNA (siRNA) by nanoparticles, including biodegradable nanoparticles, liposomes, polyplex, lipoplex and dendrimers. The characteristics, composition, preparation, applications and advantages of different nanoparticle delivery strategies are also discussed in detail, along with the recent progress of non-viral nanoparticle carrier systems for siRNA delivery in preclinical and clinical studies. Expert opinion: Non-viral carrier systems, especially nanoparticles, have been investigated extensively for siRNA delivery, and may be utilized in clinical applications in the future. So far, a few preliminary clinical trials of nanoparticles have produced promising results. However, further research is still req...
TL;DR: The authors expect that the highly versatile nature of the LbL assembly can overcome any remaining practical difficulties in delivering therapeutics, because the layer structure, component selection, and the surface nature including biocompatibility, degradability and size/dimension are all adjustable.
Abstract: Introduction: High-performance drug delivery systems are always made through assembly and hybridization of multiple components, each of which possesses its own role within the unified delivery function. The layer-by-layer (LbL) adsorption technique offers huge freedom in material selection and flexibility of structural design, which are fully matched with the fabrication needs of drug delivery materials requiring complicated designs. Areas covered: In this review, film-type LbL assemblies and their drug delivery application are focused on, with selected examples from recent years. In addition to a description of the general progress of this technique in bio-related areas, examples of the delivery of low-molecular-mass drugs, DNA, peptides and proteins are summarized, as well as recent advances in film structures composed of organic/inorganic hybrids. Expert opinion: The authors expect that the highly versatile nature of the LbL assembly can overcome any remaining practical difficulties in delivering thera...
TL;DR: The liquisolid technology has the capability to slow down drug release and allows preparing sustained release tablets with zero order drug release pattern and the excipients required for this technology are conventional and commonly available in the market.
Abstract: Introduction: Today, the properties of many new chemical entities have shifted towards higher molecular weights and this in turn increases the lipophilicity hence decreasing aqueous solubility The low solubility of drugs usually has in vivo consequences such as low bioavailability, increased chance of food effect and incomplete release from the dosage form Areas covered: The present review discusses the advantages of the liquisolid technology in formulation design of poorly water soluble drugs for dissolution enhancement and highly water soluble drugs for slow release pattern Expert opinion: With the advent of high throughput screening and combinatorial chemistry, it has been shown that most of the new chemical entities have a high lipophilicity and poor aqueous solubility, hence poor bioavailability In order to improve the bioavailability, the release rate of these drugs should be enhanced Although there are multiple technologies to tackle this issue, they are not cost effective due to the involveme
TL;DR: The various cellular pathways for NP uptake, and the factors affecting NP uptake and interactions with cells are described, to help in the future design of NPs for effective and targeted drug delivery.
Abstract: Introduction: Nanoparticles (NPs) are used extensively in drug delivery. They are administered through various routes in the host, and their uptake by the cellular environment has been observed in several pathways. After uptake, NPs interact with cells to different extents, depending on their size, shape, surface properties, ligands tagged to the surface and tumor architecture. Complete understanding of such cellular uptake mechanisms and interactions of NPs is important for their effective use in drug delivery. Areas covered: This article describes the various cellular pathways for NP uptake, and the factors affecting NP uptake and interactions with cells. Understanding these two important aspects will help in the future design of NPs for effective and targeted drug delivery. Expert opinion: Surface charge and ligands tagged on the surface of NPs play a critical role in their uptake and interaction with cells; so surface modifications of NPs can offer increased drug delivery effectiveness, for example, t...
TL;DR: Although siRNA therapeutics suffers from problems related to off-target effects and non-specific gene silencing, these problems can be overcome by reducing the nanoparticle size, improving the targeting efficiency and by modifying the primary sequence of the siRNA.
Abstract: Introduction: The discovery of synthetic small interfering RNA (siRNA) has led to a surge of interest in harnessing RNA interference (RNAi) technology for biomedical applications and drug development. Even though siRNA can be a powerful therapeutic drug, its delivery remains a major challenge, due to the difficulty in its cellular uptake. Naked siRNA has a biological half-life of less than an hour in human plasma. To increase the lifetime and improve its therapeutic efficacy, non-viral vectors have been developed. As a natural evolution, cyclodextrins (CDs), which are natural cyclic oligosaccharides, have recently been applied as delivery vehicles for siRNA, and this in turn, has led to a surge of interest in this area. Areas covered: This review discusses the recent advances made in the design of delivery strategies for siRNA, focusing on CD-based delivery vectors, because these have demonstrated clinical success. The methods of preparation of CD-based vectors, their characterization, transfection effici...
TL;DR: The Buchi Nano Spray Dryer B-90 offers a new, simple and alternative approach for the production of nanoparticles suited for a variety of drug delivery applications and has to contend with the issue of adequate redispersibility of the primary particles to reap the full benefits of nanosizing.
Abstract: Introduction: Spray drying is an extremely well-established technology for the production of micro-particulate powders suited for a variety of drug delivery applications. In recent years, the rise ...
TL;DR: In this article, the authors describe a complex and highly efficient dietary uptake system for Vitamin B12 (B12) in mammals, which consists of a multicell uptake pathway consisting of a...
Abstract: Importance of the field: Vitamin B12 (B12) is a rare and vital micronutrient for which mammals have developed a complex and highly efficient dietary uptake system. This uptake pathway consists of a...
TL;DR: This review focuses on the ways in which peptides and proteins interact with surfaces and interfaces, and the effect these interactions have on the stability and safety of the active protein in pharmaceutical formulations.
Abstract: Introduction: In the area of peptide and protein drug products, interfaces are present as part of the basic liquid formulation, when freeze-dried formulations are reconstituted and when particulate delivery systems are prepared. Proteins are known to interact with these interfaces, and the effects seen are often irreversible adsorption and structural changes. Areas covered: This review focuses on the ways in which peptides and proteins interact with surfaces and interfaces, and the effect these interactions have on the stability and safety of the active protein in pharmaceutical formulations. It illustrates, through examples, what can be determined by an adsorption study, and what can change when either the protein or the interfaces are modified. Last but not least, it addresses the value of these studies. The reader will gain an update on the basics of protein adsorption, with a focus on pharmaceutically relevant interfaces and recent advances in the field. Expert opinion: Protein adsorption is widely st...
TL;DR: This review elucidates the unique features of current commercially available or highly promising ODT and thin-film technologies, along with taste-masking approaches used in the manufacturing of oral solid dosage forms, and discusses the advantages and limitations of each technology.
Abstract: Introduction: In the last decade the development of orally disintegrating tablets (ODTs) and thin-film platforms has grown enormously in the field of pharmaceutical industry. A wide variety of new masking technologies combined with the aforementioned platforms have been developed in order to mask the taste of bitter active substances and achieve patient compliance. The commercial success and viability of such products requires the development of robust formulations with excellent palatability, disintegration times, physicochemical stability and pharmacokinetic profiles. Areas covered: In this review, emerging taste-masking technologies applied to solid dosage form manufacturing are summarized. The unique features and principles of taste-masking approaches used with ODT platforms are discussed, including the advantages and limitations of each technology. A brief discussion is also included on the taste masking of thin-film technologies, owing to their similar applications and requirements. Expert opinion: ...
TL;DR: An overview of the different drug delivery systems that exist which aim to improve the permeation of drugs through the skin, focusing on the use of charged liposomes for transdermal delivery, and a classification of such liposome based on the origin of the charge given to the vesicles is proposed.
Abstract: Introduction: In recent years, there has been increased interest in developing charged liposomes as carriers for transdermal drug delivery. It is necessary to modify the basic composition of the liposomes in order to enhance the penetration properties of the vesicles through the skin. Charged liposomes offer several advantages compared with previous drug delivery systems. Areas covered: This paper provides a brief overview of the different drug delivery systems that exist which aim to improve the permeation of drugs through the skin, focusing on the use of charged liposomes for transdermal delivery. We propose a classification of such liposomes based on the origin of the charge given to the vesicles. Expert opinion: Despite the advances that are occurring in the design of charged liposomes for transdermal drug delivery, the long-term stability continues to be a drawback in such systems. The presence of charge on the surface of the vesicles favors the electrostatic repulsion among them, creating a ζ potent...
TL;DR: An overview about the multi-agent delivery systems developed in the last decade for differential release in combination therapy, developed over the last 10 years, has been collected and summarized.
Abstract: Introduction: Combination therapy with multiple therapeutic agents has wide applicability in medical and surgical treatment, especially in the treatment of cancer. Thus, new drug delivery systems that can differentially release two or more drugs are desired. Utilizing new techniques to engineer the established drug delivery systems and synthesizing new materials and designing carriers with new structures are feasible ways to fabricate proper multi-agent delivery systems, which are critical to meet requirements in the clinic and improve therapeutic efficacy. Areas covered: This paper aims to give an overview about the multi-agent delivery systems developed in the last decade for differential release in combination therapy. Multi-agent delivery systems from nanoscale to bulk scale, such as liposomes, micelles, polymer conjugates, nano/micorparticles and hydrogels, developed over the last 10 years, have been collected and summarized. The characteristics of different delivery systems are described and discuss...
TL;DR: The most currently used methods to produce solid dispersions, such as the fusion method, hot melt extrusion, spray drying, freeze drying and supercritical fluid precipitation, are reviewed in this paper.
Abstract: Introduction: Many new drug substances have low aqueous solubility which can cause poor bioavailability after oral administration. The application of solid dispersions is a useful method to increase the dissolution rate of these drugs and thereby improve their bioavailability. So far, several methods have been developed to prepare solid dispersions. To obtain a product with the desired attributes, both the formulation and production processes should be considered. Areas covered: The most currently used methods to produce solid dispersions, such as the fusion method, hot melt extrusion, spray drying, freeze drying and supercritical fluid precipitation, are reviewed in this paper. In addition, the physicochemical characteristics of the obtained solid dispersions are discussed. Expert opinion: Solid dispersions can be successfully prepared by simple fusion, hot melt extrusion, spray drying, freeze drying and supercritical fluid precipitation. Hot melt extrusion, spray drying and freeze drying are processes t...