The miniemulsion process allows the formation of complex polymer nanoparticles and the encapsulation of widely varying materials into a polymer shell (see examples). Functionalization of the ...nanoparticles can be easily carried out, and polymerization to form polymer nanoparticles can be performed in environmentally friendly solvents, such as water.The miniemulsion process allows the formation of complex structured polymeric nanoparticles and the encapsulation of a solid or liquid, an inorganic or organic, or a hydrophobic or hydrophilic material into a polymer shell. Many different materials, ranging from organic and inorganic pigments, magnetite, or other solid nanoparticles, to hydrophobic and hydrophilic liquids, such as fragrances, drugs, or photoinitators, can be encapsulated. Functionalization of the nanoparticles can also be easily obtained. Compared to polymerization processes in organic solvents, polymerization to obtain polymeric nanoparticles can be performed in environmentally friendly solvents, usually water.
Stimuli-responsive microgels represent a highly interesting and unique class of materials since they exhibit exceptional properties which stem from the particular combination of their colloidal ...nature with their internal network structure. While this fascinating characteristic feature has been exploited in various different research fields and applications, the essential commonality for the successful development of all those diverse materials is a precise design of the respective microgels to adjust their functionality to a specific application. Regarding the delivery of functional compounds in particular, one of the main tasks is to combine an efficient loading process with a well defined release profile. A basic requirement to achieve this goal is a profound understanding of the underlying concepts of these material's features and the impact of these basic models on the design and preparation of such highly functional materials exhibiting tailor-made properties. Therefore, in this review we present some of the important fundamental examinations on the influence of (tunable) network characteristics on loading and release profiles, basic synthetic concepts to realize these concepts and highlight several examples of different approaches to stimuli-responsive microgels for loading and release applications. By this, we wish to give the reader a broad overview of the design criteria and practical methodologies to control the functionality of microgels in order to encourage further development of highly interesting concepts and materials in this area of materials science.
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Isothermal titration calorimetry (ITC) is a complementary technique that can be used for investigations of protein adsorption on nanomaterials, as it quantifies the thermodynamic parameters of ...intermolecular interactions in situ. As soon as nanomaterials enter biological media, a corona of proteins forms around the nanomaterials, which influences the surface properties and therefore the behavior of nanomaterials tremendously. ITC enhances our understanding of nanoparticle-protein interactions, as it provides information on binding affinity (in form of association constant K
), interaction mechanism (in form of binding enthalpy ΔH, binding entropy ΔS and Gibbs free energy ΔG) and binding stoichiometry n. Therefore, as a complementary method, ITC enhances our mechanistic understanding of the protein corona. In this minireview, the information obtained from a multitude of ITC studies regarding different nanomaterials and proteins are gathered and relations between nanomaterials' properties and their resulting interactions undergone with proteins are deduced. Nanomaterials formed of a hydrophilic material without strongly charged surface and steric stabilization experience the weakest interactions with proteins. As a result, such nanomaterials undergo the least unspecific protein-interactions and are most promising for allowing an engineering of the protein corona.
Cells are integral to all forms of life due to their compartmentalization by the plasma membrane. However, living organisms are immensely complex. Thus there is a need for simplified and controllable ...models of life for a deeper understanding of fundamental biological processes and man-made applications. This is where the bottom-up approach of synthetic biology comes from: a stepwise assembly of biomimetic functionalities ultimately into a protocell. A fundamental feature of such an endeavor is the generation and control of model membranes such as liposomes and polymersomes. We compare and contrast liposomes and polymersomes for a better a priori choice and design of vesicles and try to understand the advantages and shortcomings associated with using one or the other in many different aspects (properties, synthesis, self-assembly, applications) and which aspects have been studied and developed with each type and update the current development in the field.
Large-scale photochemical synthesis of high value chemicals under mild conditions is an ideal method of green chemical production. However, a scalable photocatalytic process has been barely reported ...due to the costly preparation, low stability of photosensitizers and critical reaction conditions required for classical photocatalysts. Here, we report the merging of flow chemistry with heterogeneous photoredox catalysis for the facile production of high value compounds in a continuous flow reactor with visible light at room temperature in air. In the flow reactor system, polymeric carbon nitrides, which are cheap, sustainable and stable heterogeneous photocatalysts, are immobilized onto glass beads and fibers, demonstrating a highly flexible construction possibility for devices of the photocatalytic materials. As an example of the production of high value chemicals, important chemical structures such as cyclobutanes, which are basic building blocks for many pharmaceutical compounds, like magnosalin, are synthesized in flow with high catalytic efficiency and stability.
In recent years the littering of plastics and the problems related to their persistence in the environment have become a major focus in both research and the news. Biodegradable polymers like ...poly(lactic acid) are seen as a suitable alternative to commodity plastics. However, poly(lactic acid) is basically non‐degradable in seawater. Similarly, the degradation rate of other biodegradable polymers also crucially depends on the environments they end up in, such as soil or marine water, or when used in biomedical devices. In this Minireview, we show that biodegradation tests carried out in artificial environments lack transferability to real conditions and, therefore, highlight the necessity of environmentally authentic and relevant field‐testing conditions. In addition, we focus on ecotoxicological implications of biodegradable polymers. We also consider the social aspects and ask how biodegradable polymers influence consumer behavior and municipal waste management. Taken together, this study is intended as a contribution towards evaluating the potential of biodegradable polymers as alternative materials to commodity plastics.
Living in a plastic age—For most of us, life without polymers and plastics is unthinkable. A growing problem, however, is the littering of plastics and the problems related to their persistence in the environment. This Minireview is intended as a contribution towards evaluating the potential of biodegradable polymers such as poly(lactic acid) as alternative materials to commodity plastics.
The past decade has seen a significant increase in interest in the use of polymeric nanocarriers in medical applications. In particular, when used as drug vectors in targeted delivery, nanocarriers ...could overcome many obstacles for drug therapy. Nevertheless, their application is still impeded by the complex composition of the blood proteins covering the particle surface, termed the protein corona. The protein corona complicates any prediction of cell interactions, biodistribution, and toxicity. In particular, the unspecific uptake of nanocarriers is a major obstacle in clinical studies. This Minireview provides an overview of what we currently know about the characteristics of the protein corona of nanocarriers, with a focus on surface functionalization that reduces unspecific uptake (the stealth effect). The ongoing improvement of nanocarriers to allow them to meet all the requirements necessary for successful application, including targeted delivery and stealth, are further discussed.
Stealth shield: The use of nanocarriers in medical applications is complicated by the formation of a protein corona on the nanocarrier surface. This can influence interaction with cell membranes, and makes it difficult to predict cellular interactions, biodistribution, and toxicity. This Minireview provides an overview of what we know about the protein corona of nanocarriers, with a focus on surface functionalization to reduce unspecific uptake—termed the stealth effect.
The formation of nanocapsules from a modular perspective for self‐assembled nanocapsules, so‐called polymersomes, and nanocapsules with a covalently formed shell are discussed in this review. It is ...shown that there are common and comparable ways for the selective and controlled release of payloads for stimuli‐responsive systems and nanocapsule functionalization in order to use them for drug delivery and diagnostic applications.
Comparisons of polymeric nanocapsules formed by self‐assembly (polymersomes) and covalent approaches are made in terms of their characteristics, encapsulation properties, and functionalization methods. This way of understanding is significant for choosing or combining the modules for delivery or diagnostic applications in order to reach the ideal nanocarrier systems in medical technology.
The oral application of pharmaceuticals is unarguably the most convenient method of application. Especially for protein- or peptide-based drugs, however, the effectiveness is significantly reduced ...due to enzymatic digestion in the stomach as well as a poor bioavailability in the small intestine. For these difficult formulations, the encapsulation into nanocarriers would protect the sensitive drug and thus could considerably improve the efficiency of oral drug delivery. In the last years, many candidate biodegradable nanomaterials for such carrier systems have been published. However, before the cargo can be released, the nanocarrier needs to cross multiple barriers of the human body, including a layer of intestinal mucus and epithelial as well as endothelial cells. For overcoming these cellular barriers, transcytosis is favored over a paracellular transport for most nanomaterials as paracellular transport routes lack selectivity of transported molecules once opened up. The exact mechanisms behind the transcellular translocations are up to now still not completely understood. For the vast majority of nanocarriers, the rate of transcellular transport is not sufficient to realize their application in oral drug delivery. Especially trafficking into the endolysosomal pathway often marks a key problem. In this review, we focus on the molecular mechanisms of overcoming cellular barriers, especially transcytosis, and highlight difficulties of oral drug delivery via nanocarriers.
The use of nanocarriers in biology and medicine is complicated by the current need to understand how nanoparticles interact in complex biological surroundings. When nanocarriers come into contact ...with serum, proteins immediately adsorb onto their surface, forming a protein corona which defines their biological identity. Although the composition of the protein corona has been widely determined by proteomics, its morphology still remains unclear. In this study we show for the first time the morphology of the protein corona using transmission electron microscopy. We are able to demonstrate that the protein corona is not, as commonly supposed, a dense, layered shell coating the nanoparticle, but an undefined, loose network of proteins. Additionally, we are now able to visualize and discriminate between the soft and hard corona using centrifugation-based separation techniques together with proteomic characterization. The protein composition of the ∼15 nm hard corona strongly depends on the surface chemistry of the respective nanomaterial, thus further affecting cellular uptake and intracellular trafficking. Large diameter protein corona resulting from pre-incubation with soft corona or Apo-A1 inhibits cellular uptake, confirming the stealth-effect mechanism. In summary, the knowledge on protein corona formation, composition and morphology is essential to design therapeutic effective nanoparticle systems.
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