Nano-in-Microparticles for Aerosol Delivery of Antibiotic-Loaded, Fucose-Derivatized, and Macrophage-Targeted Liposomes to Combat Mycobacterial Infections: In Vitro Deposition, Pulmonary Barrier Interactions, and Targeted Delivery.

Nontuberculous mycobacterial infections rapidly emerge and demand potent medications to cope with resistance. In this context, targeted loco-regional delivery of aerosol medicines to the lungs is an advantage. However, sufficient antibiotic delivery requires engineered aerosols for optimized deposition. Here, the effect of bedaquiline-encapsulating fucosylated versus nonfucosylated liposomes on cellular uptake and delivery is investigated. Notably, this comparison includes critical parameters for pulmonary delivery, i.e., aerosol deposition and the noncellular barriers of pulmonary surfactant (PS) and mucus. Targeting increases liposomal uptake into THP-1 cells as well as peripheral blood monocyte- and lung-tissue derived macrophages. Aerosol deposition in the presence of PS, however, masks the effect of active targeting. PS alters antibiotic release that depends on the drug's hydrophobicity, while mucus reduces the mobility of nontargeted more than fucosylated liposomes. Dry-powder microparticles of spray-dried bedaquiline-loaded liposomes display a high fine particle fraction of >70%, as well as preserved liposomal integrity and targeting function. The antibiotic effect is maintained when deposited as powder aerosol on cultured Mycobacterium abscessus. When treating M. abscessus infected THP-1 cells, the fucosylated variant enabled enhanced bacterial killing, thus opening up a clear perspective for the improved treatment of nontuberculous mycobacterial infections.

Conformational states of human rat sarcoma (Ras) protein complexed with its natural ligand GTP and their role for effector interaction and GTP hydrolysis.

The guanine nucleotide-binding protein Ras exists in solution in two different conformational states when complexed with different GTP analogs such as GppNHp or GppCH(2)p. State 1 has only a very low affinity to effectors and seems to be recognized by guanine nucleotide exchange factors, whereas state 2 represents the high affinity effector binding state. In this work we investigate Ras in complex with the physiological nucleoside triphosphate GTP. By polarization transfer (31)P NMR experiments and effector binding studies we show that Ras(wt)·Mg(2+)·GTP also exists in a dynamical equilibrium between the weakly populated conformational state 1 and the dominant state 2. At 278 K the equilibrium constant between state 1 and state 2 of C-terminal truncated wild-type Ras(1-166) K(12) is 11.3. K(12) of full-length Ras is >20, suggesting that the C terminus may also have a regulatory effect on the conformational equilibrium. The exchange rate (k(ex)) for Ras(wt)·Mg(2+)·GTP is 7 s(-1) and thus 18-fold lower compared with that found for the Ras·GppNHp complex. The intrinsic GTPase activity substantially increases after effector binding for the switch I mutants Ras(Y32F), (Y32R), (Y32W), (Y32C/C118S), (T35S), and the switch II mutant Ras(G60A) by stabilizing state 2, with the largest effect on Ras(Y32R) with a 13-fold increase compared with wild-type. In contrast, no acceleration was observed in Ras(T35A). Thus Ras in conformational state 2 has a higher affinity to effectors as well as a higher GTPase activity. These observations can be used to explain why many mutants have a low GTPase activity but are not oncogenic.

Spray-dried lactose-leucine microparticles for pulmonary delivery of antimycobacterial nanopharmaceuticals.

Pulmonary delivery of nanocarriers for novel antimycobacterial compounds is challenging because the aerodynamic properties of nanomaterials are sub-optimal for such purposes. Here, we report the development of dry powder formulations for nanocarriers containing benzothiazinone 043 (BTZ) or levofloxacin (LVX), respectively. The intricacy is to generate dry powder aerosols with adequate aerodynamic properties while maintaining both nanostructural integrity and compound activity until reaching the deeper lung compartments. Microparticles (MPs) were prepared using vibrating mesh spray drying with lactose and leucine as approved excipients for oral inhalation drug products. MP morphologies and sizes were measured using various biophysical techniques including determination of geometric and aerodynamic mean sizes, X-ray diffraction, and confocal and focused ion beam scanning electron microscopy. Differences in the nanocarriers' characteristics influenced the MPs' sizes and shapes, their aerodynamic properties, and, hence, also the fraction available for lung deposition. Spay-dried powders of a BTZ nanosuspension, BTZ-loaded silica nanoparticles (NPs), and LVX-loaded liposomes showed promising respirable fractions, in contrast to zirconyl hydrogen phosphate nanocontainers. While the colloidal stability of silica NPs was improved after spray drying, MPs encapsulating either BTZ nanosuspensions or LVX-loaded liposomes showed the highest respirable fractions and active pharmaceutical ingredient loads. Importantly, for the BTZ nanosuspension, biocompatibility and in vitro uptake by a macrophage model cell line were improved even further after spray drying.

Simplified 89Zr-Labeling Protocol of Oxine (8-Hydroxyquinoline) Enabling Prolonged Tracking of Liposome-Based Nanomedicines and Cells.

In this work, a method for the preparation of the highly lipophilic labeling synthon [89Zr]Zr(oxinate)4 was optimized for the radiolabeling of liposomes and human induced pluripotent stem cells (hiPSCs). The aim was to establish a robust and reliable labeling protocol for enabling up to one week positron emission tomography (PET) tracing of lipid-based nanomedicines and transplanted or injected cells, respectively. [89Zr]Zr(oxinate)4 was prepared from oxine (8-hydroxyquinoline) and [89Zr]Zr(OH)2(C2O4). Earlier introduced liquid-liquid extraction methods were simplified by the optimization of buffering, pH, temperature and reaction times. For quality control, thin-layer chromatography (TLC), size-exclusion chromatography (SEC) and centrifugation were employed. Subsequently, the 89Zr-complex was incorporated into liposome formulations. PET/CT imaging of 89Zr-labeled liposomes was performed in healthy mice. Cell labeling was accomplished in PBS using suspensions of 3 × 106 hiPSCs, each. [89Zr]Zr(oxinate)4 was synthesized in very high radiochemical yields of 98.7% (96.8% ± 2.8%). Similarly, high internalization rates (≥90%) of [89Zr]Zr(oxinate)4 into liposomes were obtained over an 18 h incubation period. MicroPET and biodistribution studies confirmed the labeled nanocarriers' in vivo stability. Human iPSCs incorporated the labeling agent within 30 min with ~50% efficiency. Prolonged PET imaging is an ideal tool in the development of lipid-based nanocarriers for drug delivery and cell therapies. To this end, a reliable and reproducible 89Zr radiolabeling method was developed and tested successfully in a model liposome system and in hiPSCs alike.

Fucosylated lipid nanocarriers loaded with antibiotics efficiently inhibit mycobacterial propagation in human myeloid cells.

Antibiotic treatment of tuberculosis (TB) is complex, lengthy, and can be associated with various adverse effects. As a result, patient compliance often is poor, thus further enhancing the risk of selecting multi-drug resistant bacteria. Macrophage mannose receptor (MMR)-positive alveolar macrophages (AM) constitute a niche in which Mycobacterium tuberculosis replicates and survives. Therefore, we encapsulated levofloxacin in lipid nanocarriers functionalized with fucosyl residues that interact with the MMR. Indeed, such nanocarriers preferentially targeted MMR-positive myeloid cells, and in particular, AM. Intracellularly, fucosylated lipid nanocarriers favorably delivered their payload into endosomal compartments, where mycobacteria reside. In an in vitro setting using infected human primary macrophages as well as dendritic cells, the encapsulated antibiotic cleared the pathogen more efficiently than free levofloxacin. In conclusion, our results point towards carbohydrate-functionalized nanocarriers as a promising tool for improving TB treatment by targeted delivery of antibiotics.

Fundamental link between folding states and functional states of proteins.

Folding and function of proteins are two aspects of proteins which are usually considered as basically unrelated phenomena that are optimized by evolution independently. From the funnel model of folding/unfolding and the associated energy landscape, we infer the paradigm that the minimum number of folding intermediates is determined by the number of all functional states of a protein ("essential" folding intermediates). Here, we demonstrate the supposed fundamental link using the Ras protein complexed with the GTP analogue GppNHp that occurs in two structural states coexisting in solution. State 2 was shown earlier to represent the effector interacting state, and the function of state 1 was hitherto unknown. By (31)P NMR spectroscopy, we demonstrate that state 1 represents the conformation interacting with guanine nucleotide exchange factors (GEFs). Denaturation experiments of the protein with a chaotropic reagent show that both functional states coexist during folding and unfolding. Application of high pressure represents another perturbation of the energy landscape, leading to an increased population of the state 1 as observed by NMR spectroscopy. The specific volume difference between the two states DeltaV(12) is 17.2 +/- 0.5 mL mol(-1), indicating that state 1 represents a more open conformation of the protein. The free energies of stabilization for state 1 and state 2 at 278 K can be determined as 8.3 and 9.8 kJ mol(-1), respectively.

Antigen presenting cell-selective drug delivery by glycan-decorated nanocarriers.

Targeted drug delivery systems hold promise for selective provision of active compounds to distinct tissues or cell subsets. Thus, locally enhanced drug concentrations are obtained that would confer improved efficacy. As a consequence adverse effects should be diminished, as innocent bystander cells are less affected. Currently, several controlled drug delivery systems based on diverse materials are being developed. Some systems exhibit material-associated toxic effects and/or show low drug loading capacity. In contrast, liposomal nanocarriers are particularly favorable because they are well tolerated, poorly immunogenic, can be produced in defined sizes, and offer a reasonable payload capacity. Compared with other immune cells, professional antigen-presenting cells (APCs) demonstrate enhanced liposome uptake mediated by macropinocytosis, phagocytosis and presumably also by clathrin- and caveolae-mediated endocytosis. In order to further enhance the targeting efficacy toward APCs, receptor-mediated uptake appears advisable. Since APC subsets generally do not express single linage-specific receptors, members of the C-type lectin receptor (CLR) family are compelling targets. Examples of CLR expressed by APCs include DEC-205 (CD205) expressed by myeloid dendritic cells (DC) and monocytes, the mannose receptor C type 1 (MR, CD206) expressed by DC, monocytes and macrophages, DC-SIGN (CD209) expressed by DC, and several others. These receptors bind glycans, which are typically displayed by pathogens and thus support pathogen uptake and endocytosis. Further research will elucidate whether glycan-decorated liposomes will not only enhance APCs targeting but also enable preferential delivery of their payload to discrete subcellular compartments.

Monitoring the degradation of reduction-sensitive gene carriers with fluorescence spectroscopy and flow cytometry.

Polycations like poly(ethylene imine) (PEI) or poly(L-lysine) (pLL) form nanometer-sized complexes with nucleic acids (polyplexes) which can be used for gene delivery. It is known that the properties of these -carriers can be greatly improved by introducing disulfide bridges on the polymers, thus making them reduction sensitive. However, little is known about how such modified carriers behave intracellularly. Here, we describe a method that uses the reduction-sensitive fluorescent dye BODIPY FL L-cystine to label PEI and pLL. Our probe is activated under reductive conditions leading to strongly increased fluorescence intensity. Subsequently, we show how the intracellular route of polyplexes made from these labeled polymers can be monitored by flow cytometry.

Delivery of nucleic acids via disulfide-based carrier systems.

Nucleic acids are not only expected to assume a pivotal position as "drugs" in the treatment of genetic and acquired diseases, but could also act as molecular cues to control the microenvironment during tissue regeneration. Despite this promise, the efficient delivery of nucleic acids to their side of action is still the major hurdle. One among many prerequisites for a successful carrier system for nucleic acids is high stability in the extracellular environment, accompanied by an efficient release of the cargo in the intracellular compartment. A promising strategy to create such an interactive delivery system is to exploit the redox gradient between the extra- and intracellular compartments. In this review, emphasis is placed on the biological rationale for the synthesis of redox sensitive, disulfide-based carrier systems, as well as the extra- and intracellular processing of macromolecules containing disulfide bonds. Moreover, the basic synthetic approaches for introducing disulfide bonds into carrier molecules, together with examples that demonstrate the benefit of disulfides at the individual stages of nucleic acid delivery, will be presented.

Mechanistic investigation of poly(ethylene imine)-based siRNA delivery: disulfide bonds boost intracellular release of the cargo.

Poly(ethylene imine) (PEI) has gained increasing attention in the delivery of small interfering RNAs (siRNAs) into cells. In order to further optimize PEI for this application, the first goal of this study was to examine particular steps of siRNA delivery with various PEI derivatives as carriers. Furthermore, the hypothesis that disulfide cleavable carrier systems are favorable for the release of siRNA into the cell cytoplasm was investigated. Flow cytometry and confocal microscopy were used to assess the cellular uptake and intracellular distribution of siRNA, which were then related to gene silencing efficacy. We observed a strong correlation between cellular uptake and RNAi activity. The cellular uptake of siRNA was more efficient with increasing branching of the polymer, i.e. linear PEI (lPEI) 5 kDa < lPEI cross-linked via disulfide bonds (ssPEI) < branched PEI (bPEI) 25 kDa. However, it was also evident that the siRNA release from the carrier, which was promoted by ssPEI, played an important role in the accessibility of siRNA for the gene silencing complex. Therefore, we suggest that a combination of a high branching density and reductively cleavable bonds within the PEI-based carrier system could be one possible step towards improving siRNA delivery.