Microtubule involvement in the intracellular dynamics for gene transfection mediated by cationic liposomes

The alpha-adrenergic antagonist prazosin promotes cytosolic siRNA delivery from lysosomal compartments

The widespread use of small interfering RNA (siRNA) is limited by the multiple extra- and intracellular barriers upon in vivo administration. Hence, suitable delivery systems, based on siRNA encapsulation in nanoparticles or its conjugation to targeting ligands, have been developed. Nevertheless, at the intracellular level, these state-of-the-art delivery systems still suffer from a low endosomal escape efficiency. Consequently, the bulk of the endocytosed siRNA drug rapidly accumulates in the lysosomal compartment. We recently reported that a wide variety of cationic amphiphilic drugs (CADs) can promote small nucleic acid delivery from the endolysosomal compartment into the cytosol via transient induction of lysosomal membrane permeabilization. Here, we describe the identification of alternate siRNA delivery enhancers from the NIH Clinical Compound Collection that do not have the typical physicochemical properties of CADs. Additionally, we demonstrate improved endolysosomal escape of siRNA via a cholesterol conjugate and polymeric carriers with the α1-adrenergic antagonist prazosin, which was identified as the best performing delivery enhancer from the compound screen. A more detailed assessment of the mode-of-action of prazosin suggests that a different cellular phenotype compared to typical CAD adjuvants drives cytosolic siRNA delivery. As it has been described in the literature that prazosin also induces cancer cell apoptosis and promotes antigen cross-presentation in dendritic cells, the proof-of-concept data in this work provides opportunities for the repurposing of prazosin in an anti-cancer combination strategy with siRNA.

Apolipoprotein C3 facilitates internalization of cationic lipid nanoparticles into bone marrow-derived mouse mast cells

Mast cells (MCs), are hematopoetically-derived secretory immune cells that release preformed as well as de novo synthesized inflammatory mediators in response to activation by several stimuli. Based on their role in inflammatory responses, particularly in the lung and skin, MCs provide an effective target for anti-inflammatory therapeutic strategies. Drug-delivery of lipophilic payloads to MCs can be challenging due to their functionally distinct intracellular structures. In the present study, pH-sensitive cationic lipid-based nanoparticles (LNPs) composed of DODMA, DODAP or DOTAP lipids that encapsulated a GFP or eGFP plasmid were constructed using non-turbulent microfluidic mixing. This approach achieved up to 75-92% encapsulation efficiency. Dynamic light scattering revealed a uniformly sized and homogeneous dispersion of LNPs. To promote cellular internalization, LNPs were complexed with apolipoproteins, amphipathic proteins capable of binding lipids and facilitating their transport into cells. Cryo-TEM analysis showed that LNP structure was differentially modified when associated with different types of apolipoproteins. LNP preparations made up of DODMA or DODMA, DODAP and DOTAP lipids were coated with seven apolipoproteins (Apo A1, B, C3, D, E2, E4 and H). Differentiated bone-marrow derived mouse mast cells (BMMCs) were exposed to apolipoprotein-LNP and internalization was measured using flow cytometry. Out of all the apolipoproteins tested, ApoC3 most efficiently facilitated cellular internalization of the LNP into BMMCs as determined by GFP fluorescence using flow cytometry. These effects were confirmed in a less differentiated but also interleukin-3-dependent model of mouse mast cells, MC/9. ApoC3-LNP enhanced internalization by BMMC in a concentration-dependent manner and this was significantly increased when BMMC were pre-treated with inhibitors of actin polymerization, suggesting a dependence on intracellular shuttling. Activation of peroxisome proliferator-activated receptor gamma (PPARγ) decreased ApoC3-LNP internalization and reduced the expression of apolipoprotein E receptor 2 (ApoER2), suggesting that ApoC3-LNP binding to ApoER2 may be responsible for its enhanced internalization. Furthermore, ApoC3 fails to facilitate internalization of LNPs in Lrp8^-/- KO BMMC that do not express ApoER2 on their cell surface. Altogether, our studies reveal an important role of ApoC3 in facilitating internalization of cationic LNPs into MCs.

TBK1 inhibitors enhance transfection efficiency by suppressing p62/SQSTM1 phosphorylation

DNA transfection is an essential technique in the life sciences. Non-viral transfection reagents are widely used for transfection in basic science. However, low transfection efficiency is a problem in some cell types. This low efficiency can be primarily attributed to the intracellular degradation of transfected DNA by p62-dependent selective autophagy, specifically by p62 phosphorylated at the S403 residue (p62-S403-P). To achieve efficient DNA transfection, we focused on a phosphorylation process that generates p62-S403-P and investigated whether inhibition of this process affects transfection efficiency. One of the kinases that phosphorylate p62 is TBK1. The TBK1 gene depletion in murine embryonic fibroblast cells by genome editing caused a significant reduction or loss of p62-S405-P (equivalent to human S403-P) and enhanced transfection efficiency, suggesting that TBK1 is a major kinase that phosphorylates p62 at S403. Therefore, TBK1 is a viable target for drug treatment to increase transfection efficiency. Transfection efficiency was enhanced when cells were treated with one of the following TBK1 inhibitors BX795, MRT67307, or amlexanox. This effect was synergistically improved when the two inhibitors were used in combination. Our results indicate that TBK1 inhibitors enhanced transfection efficiency by suppressing p62 phosphorylation.

Modulating intracellular pathways to improve non-viral delivery of RNA therapeutics

RNA therapeutics (e.g. siRNA, oligonucleotides, mRNA, etc.) show great potential for the treatment of a myriad of diseases. However, to reach their site of action in the cytosol or nucleus of target cells, multiple intra- and extracellular barriers have to be surmounted. Several non-viral delivery systems, such as nanoparticles and conjugates, have been successfully developed to meet this requirement. Unfortunately, despite these clear advances, state-of-the-art delivery agents still suffer from relatively low intracellular delivery efficiencies. Notably, our current understanding of the intracellular delivery process is largely oversimplified. Gaining mechanistic insight into how RNA formulations are processed by cells will fuel rational design of the next generation of delivery carriers. In addition, identifying which intracellular pathways contribute to productive RNA delivery could provide opportunities to boost the delivery performance of existing nanoformulations. In this review, we discuss both established as well as emerging techniques that can be used to assess the impact of different intracellular barriers on RNA transfection performance. Next, we highlight how several modulators, including small molecules but also genetic perturbation technologies, can boost RNA delivery by intervening at differing stages of the intracellular delivery process, such as cellular uptake, intracellular trafficking, endosomal escape, autophagy and exocytosis.

Microtubule inhibitors identified through nonbiased screening enhance DNA transfection efficiency by delaying p62-dependent ubiquitin recruitment

Ectopic gene expression is an indispensable tool in biology and medicine, but is often limited by the low efficiency of DNA transfection. We previously reported that depletion of the autophagy receptor p62/SQSTM1 enhances DNA transfection efficiency by preventing the degradation of transfected DNA. Therefore, p62 is a potential target for drugs to increase transfection efficiency. To identify such drugs, a nonbiased high-throughput screening was applied to over 4,000 compounds from the Osaka University compound library, and their p62 dependency was evaluated. The top-scoring drugs were mostly microtubule inhibitors, such as colchicine and vinblastine, and all of them showed positive effects only in the presence of p62. To understand the p62-dependent mechanisms, the time required for p62-dependent ubiquitination, which is required for autophagosome formation, was examined using polystyrene beads that were introduced into cells as materials that mimicked transfected DNA. Microtubule inhibitors caused a delay in ubiquitination. Furthermore, the level of phosphorylated p62 at S405 was markedly decreased in the drug-treated cells. These results suggest that microtubule inhibitors inhibit p62-dependent autophagosome formation. Our findings demonstrate for the first time that microtubule inhibitors suppress p62 activation as a mechanism for increasing DNA transfection efficiency and provide solutions to increase efficiency.

Single-Cell Immunoblotting based on a Photoclick Hydrogel Enables High-Throughput Screening and Accurate Profiling of Exogenous Gene Expression

Fast and accurate profiling of exogenous gene expression in host cells is crucial for studying gene function in cellular and molecular biology, but still faces the challenge of incomplete co-expression of reporter genes and target genes. Here, a single-cell transfection analysis chip (scTAC) is presented, which is based on the in situ microchip immunoblotting method, for rapid and accurate analysis of exogenous gene expression in thousands of individual host cells. scTAC not only can assign information of exogenous gene activity to specific transfected cells, but enables the acquisition of continuous protein expression even in low co-expression scenarios. It is demonstrated that scTAC can reveal the relationship of expression level between reporter genes and target genes, which is helpful for evaluating transient transfection strategy efficiency. The advantages of this method for the study of fusion protein expression and downstream protein expression in signaling pathway in rare cells are shown. Empirically, an EGFP-TSPAN8 fusion plasmid is transfected into MCF-7 breast cancer cells and the expressions of two cancer stemness biomarkers (ALDHA1 and SOX2) are analyzed. The scTAC method clearly reveals an interesting phenomenon that transfected adherent MCF-7 cells exhibit some stem cell characteristics, but they do not have stem cell appearance.

Barriers and Strategies of Cationic Liposomes for Cancer Gene Therapy

Cationic liposomes (CLs) have been regarded as the most promising gene delivery vectors for decades with the advantages of excellent biodegradability, biocompatibility, and high nucleic acid encapsulation efficiency. However, the clinical use of CLs in cancer gene therapy is limited because of many uncertain factors in vivo. Extracellular barriers such as opsonization, rapid clearance by the reticuloendothelial system and poor tumor penetration, and intracellular barriers, including endosomal/lysosomal entrapped network and restricted diffusion to the nucleus, make CLs not the ideal vector for transferring extrinsic genes in the body. However, the obstacles in achieving productive therapeutic effects of nucleic acids can be addressed by tailoring the properties of CLs, which are influenced by lipid compositions and surface modification. This review focuses on the physiological barriers of CLs against cancer gene therapy and the effects of lipid compositions on governing transfection efficiency, and it briefly discusses the impacts of particle size, membrane charge density, and surface modification on the fate of CLs in vivo, which may provide guidance for their preclinical studies.

Mechanisms of unprimed and dexamethasone-primed nonviral gene delivery to human mesenchymal stem cells

Human mesenchymal stem cells (hMSCs) are under intense study for applications of cell and gene therapeutics because of their unique immunomodulatory and regenerative properties. Safe and efficient genetic modification of hMSCs could increase their clinical potential by allowing functional expression of therapeutic transgenes or control over behavior and differentiation. Viral gene delivery is efficient, but suffers from safety issues, while nonviral methods are safe, but highly inefficient, especially in hMSCs. Our lab previously demonstrated that priming cells before delivery of DNA complexes with dexamethasone (DEX), an anti‐inflammatory glucocorticoid drug, significantly increases hMSC transfection success. This work systematically investigates the mechanisms of hMSC transfection and DEX‐mediated enhancement of transfection. Our results show that hMSC transfection and its enhancement by DEX are decreased by inhibiting classical intracellular transport and nuclear import pathways, but DEX transfection priming does not increase cellular or nuclear internalization of plasmid DNA (pDNA). We also show that hMSC transgene expression is largely affected by pDNA promoter and enhancer sequence changes, but DEX‐mediated enhancement of transfection is unaffected by any pDNA sequence changes. Furthermore, DEX‐mediated transfection enhancement is not the result of increased transgene messenger RNA transcription or stability. However, DEX‐priming increases total protein synthesis by preventing hMSC apoptosis induced by transfection, resulting in increased translation of transgenic protein. DEX may also promote further enhancement of transgenic reporter enzyme activity by other downstream mechanisms. Mechanistic studies of nonviral gene delivery will inform future rationally designed technologies for safe and efficient genetic modification of clinically relevant cell types.

A Novel 2-Methoxyestradiol Analogue Is Responsible for Vesicle Disruption and Lysosome Aggregation in Breast Cancer Cells

BACKGROUND

2-Methoxyestradiol (2ME2) is an endogenous metabolite of 17-β-estradiol with anti-proliferative and anti-angiogenic properties. Due to 2ME2's rapid metabolism and low oral bioavailability in in vivo settings, 2ME2 analogues have been designed to alleviate these issues. One of these compounds is 2-ethyl-3-O-sulphamoyl-estra-1,3,5(10)16-tetraene (ESE-16). A previous work alluded to the ability of ESE-16 to induce autophagic cell death. Therefore, we investigated the mode of action of ESE-16 by studying its effects on autophagy, vesicle formation, and lysosomal organisation.

SUMMARY

Vesicle formation and autophagy induction were analysed by transmission electron microscopy (TEM), monodansylcadaverine (MDC) staining and Lysotracker staining, while autophagosome turnover was analysed using microtubule-associated protein 1A/1B-light chain 3 (LC3 lipidation) analysis. MDC staining of acidic vesicles revealed an increase both in the number and size of vesicles after ESE-16 exposure. This was confirmed by TEM. Lysotracker staining indicated an increase in the size of lysosomes, as well as changes in their distribution within the cell. However, autophagy was not induced, since LC3 lipidation did not increase after exposure to ESE-16. Key -Messages: This study showed that ESE-16 exposure leads to the aggregation of acidic vesicles, identified as lysosomes, not accompanied by an induction of autophagy. Therefore, ESE-16 disrupts normal endocytic vesicle maturation likely through the inhibition of the microtubule function.

Exogenous chondroitin sulfate glycosaminoglycan associate with arginine-rich peptide-DNA complexes to alter their intracellular processing and gene delivery efficiency

Arginine-rich peptides have been used extensively as efficient cellular transporters. However, gene delivery with such peptides requires development of strategies to improve their efficiency. We had earlier demonstrated that addition of small amounts of exogenous glycosaminoglycans (GAGs) like heparan sulfate or chondroitin sulfate to different arginine-rich peptide-DNA complexes (polyplexes) led to an increase in their gene delivery efficiency. This was possibly due to the formation of a 'GAG coat' on the polyplex surface through electrostatic interactions which improved their extracellular stability and subsequent cellular entry. In this report, we have attempted to elucidate the differences in intracellular processing of the chondroitin sulfate (CS)-coated polyplexes in comparison to the native polyplexes by using a combination of endocytic inhibitors and co-localization with endosomal markers in various cell lines. We observed that both the native and CS-coated polyplexes are internalized by multiple endocytic pathways although in some cell lines, the coated polyplexes are taken up primarily by caveolae mediated endocytosis. In addition, the CS-coat improves the endosomal escape of the polyplexes as compared to the native polyplexes. Interestingly, during these intracellular events, exogenous CS is retained with the polyplexes until their accumulation near the nucleus. Thus we show for the first time that exogenous GAGs in small amounts improve intracellular routing and nuclear accumulation of arginine-based polyplexes. Therefore, addition of exogenous GAGs is a promising strategy to enhance the transfection efficiency of cationic arginine-rich peptides in multiple cell types.

Mechanisms of nanoparticle internalization and transport across an intestinal epithelial cell model: effect of size and surface charge

This study investigated the effect of nanoparticle size (50 and 100 nm) and surface charge on their interaction with Caco-2 monolayers as a model of the intestinal epithelium, including cell internalization pathways and the level of transepithelial transport. Initially, toxicity assays showed that cell viability and cell membrane integrity were dependent on the surface charge and applied mass, number, and total surface area of nanoparticles, as tested in two epithelial cell lines, colon carcinoma Caco-2 and airway Calu-3. This also identified suitable nanoparticle concentrations for subsequent cell uptake experiments. Nanoparticle application at doses below half maximal effective concentration (EC₅₀) revealed that the transport efficiency (ratio of transport to cell uptake) across Caco-2 cell monolayers is significantly higher for negatively charged nanoparticles compared to their positively charged counterparts (of similar size), despite the higher level of internalization of positively charged systems. Cell internalization pathways were hence probed using a panel of pharmacological inhibitors aiming to establish whether the discrepancy in transport efficiency is due to different uptake and transport pathways. Vesicular trans-monolayer transport for both positively and negatively charged nanoparticles was confirmed via inhibition of dynamin (by dynasore) and microtubule network (via nocodazole), which significantly reduced the transport of both nanoparticle systems. For positively charged nanoparticles a significant decrease in internalization and transport (46% and 37%, respectively) occurred in the presence of a clathrin pathway inhibitor (chlorpromazine), macropinocytosis inhibition (42%; achieved by 5-(N-ethyl-N-isopropyi)-amiloride), and under cholesterol depletion (38%; via methyl-β-cyclodextrin), but remained unaffected by the inhibition of lipid raft associated uptake (caveolae) by genistein. On the contrary, the most prominent reduction in internalization and transport of negatively charged nanoparticles (51% and 48%, respectively) followed the inhibition of lipid raft-associated pathway (caveolae inhibition by genistein) but was not significantly affected by the inhibition of clathrin pathway.

Uptake and transfection efficiency of PEGylated cationic liposome-DNA complexes with and without RGD-tagging

Steric stabilization of cationic liposome-DNA (CL-DNA) complexes is required for in vivo applications such as gene therapy. PEGylation (PEG: poly(ethylene glycol)) of CL-DNA complexes by addition of PEG2000-lipids yields sterically stabilized nanoparticles but strongly reduces their gene delivery efficacy. PEGylation-induced weakening of the electrostatic binding of CL-DNA nanoparticles to cells (leading to reduced uptake) has been considered as a possible cause, but experimental results have been ambiguous. Using quantitative live-cell imaging in vitro, we have investigated cell attachment and uptake of PEGylated CL-DNA nanoparticles with and without a custom synthesized RGD-peptide grafted to the distal ends of PEG2000-lipids. The RGD-tagged nanoparticles exhibit strongly increased cellular attachment as well as uptake compared to nanoparticles without grafted peptide. Transfection efficiency of RGD-tagged PEGylated CL-DNA NPs increases by about an order of magnitude between NPs with low and high membrane charge density (σM; the average charge per unit area of the membrane; controlled by the molar ratio of cationic to neutral lipid), even though imaging data show that uptake of RGD-tagged particles is only slightly enhanced by high σM. This suggests that endosomal escape and, as a result, transfection efficiency of RGD-tagged NPs is facilitated by high σM. We present a model describing the interactions between PEGylated CL-DNA nanoparticles and the anionic cell membrane which shows how the PEG grafting density and membrane charge density affect adhesion of nanoparticles to the cell surface.

New views and insights into intracellular trafficking of drug-delivery systems by fluorescence fluctuation spectroscopy

Biomaterials in the nanometer size range can be engineered for site-specific delivery of drugs after injection into the blood circulation. However, translation of such nanomedicines from the bench to the bedside is still hindered by many extracellular and intracellular barriers. To realize the concept of targeted drug delivery with nanomedicines, research groups are studying intensively the extra- and intra-cellular mechanisms involved as a response to the physicochemical properties of the nanomedicines. In this review, we highlight the contributions of fluorescence fluctuations spectroscopy techniques to better understand, and in turn to bypass, the major hurdles to therapeutic delivery, focusing mostly on the intracellular dynamics of drug-delivery systems.

Insight concerning the mechanism of therapeutic ultrasound facilitating gene delivery: increasing cell membrane permeability or interfering with intracellular pathways?

Nonviral gene delivery methods encounter major barriers in plasmid DNA (pDNA) trafficking toward the nucleus. The present study aims to understand the role and contribution of therapeutic ultrasound (TUS), if any, in pDNA trafficking in primary cells such as fibroblasts and cell lines (e.g., baby hamster kidney [BHK]) during the transfection process. Using compounds that alter the endocytic pathways and the cytoskeletal network, we show that after TUS application, pDNA trafficking in the cytoplasm is not mediated by endocytosis or by the cytoskeletal network. Transfection studies and confocal analyses showed that the actin fibers impeded TUS-mediated transfection in BHK cells, but not in fibroblasts. Flow cytometric analyses indicated that pDNA uptake by cells occurs primarily when the pDNA is added before and not after TUS application. Taken together, these results suggest that TUS by itself operates as a mechanical force driving the pDNA through the cell membrane, traversing the cytoplasmic network and into the nucleus.

Tubulation of endosomal structures in human dendritic cells by Toll-like receptor ligation and lymphocyte contact accompanies antigen cross-presentation

Mouse dendritic cells (DCs) can rapidly extend their Class II MHC-positive late endosomal compartments into tubular structures, induced by Toll-like receptor (TLR) triggering. Within antigen-presenting DCs, tubular endosomes polarize toward antigen-specific CD4(+) T cells, which are considered beneficial for their activation. Here we describe that also in human DCs, TLR triggering induces tubular late endosomes, labeled by fluorescent LDL. TLR triggering was insufficient for induced tubulation of transferrin-positive endosomal recycling compartments (ERCs) in human monocyte-derived DCs. We studied endosomal remodeling in human DCs in co-cultures of DCs with CD8(+) T cells. Tubulation of ERCs within human DCs requires antigen-specific CD8(+) T cell interaction. Tubular remodeling of endosomes occurs within 30 min of T cell contact and involves ligation of HLA-A2 and ICAM-1 by T cell-expressed T cell receptor and LFA-1, respectively. Disintegration of microtubules or inhibition of endosomal recycling abolished tubular ERCs, which coincided with reduced antigen-dependent CD8(+) T cell activation. Based on these data, we propose that remodeling of transferrin-positive ERCs in human DCs involves both innate and T cell-derived signals.

Mechanistic understanding of gene delivery mediated by highly efficient multicomponent envelope-type nanoparticle systems

We packaged condensed DNA/protamine particles in multicomponent envelope-type nanoparticle systems (MENS) combining different molar fractions of the cationic lipids 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) and 3β-[N-(N,N-dimethylaminoethane)-carbamoyl] cholesterol (DC-Chol) and the zwitterionic lipids dioleoylphosphocholine (DOPC) and dioleoylphosphatidylethanolamine (DOPE). Dynamic light scattering (DLS) and microelectrophoresis allowed us to identify the cationic lipid/DNA charge ratio at which MENS are small sized and positively charged, while synchrotron small-angle X-ray scattering (SAXS) and atomic force microscopy (AFM) revealed that MENS are well-shaped DNA/protamine particles covered by a lipid monobilayer. Transfection efficiency (TE) experiments indicate that a nanoparticle formulation, termed MENS-3, was not cytotoxic and highly efficient to transfect Chinese hamster ovary (CHO) cells. To rationalize TE, we performed a quantitative investigation of cell uptake, intracellular trafficking, endosomal escape, and final fate by laser scanning confocal microscopy (LSCM). We found that fluid-phase macropinocytosis is the only endocytosis pathway used by MENS-3. Once taken up by the cell, complexes that are actively transported by microtubules frequently fuse with lysosomes, while purely diffusing systems do not. Indeed, spatiotemporal image correlation spectroscopy (STICS) clarified that MENS-3 mostly exploit diffusion to move in the cytosol of CHO cells, thus explaining the high TE levels observed. Also, MENS-3 exhibited a marked endosomal rupture ability resulting in extraordinary DNA release. The lipid-dependent and structure-dependent TE boost suggests that efficient transfection requires both the membrane-fusogenic activity of the nanocarrier envelope and the employment of lipid species with intrinsic endosomal rupture ability.

The role of cytoskeleton networks on lipid-mediated delivery of DNA

BACKGROUND

Lipid-mediated delivery of DNA is hindered by extracellular and intracellular barriers that significantly reduce the transfection efficiency of synthetic nonviral vectors.

RESULTS

In this study we investigated the role of the actin and microtubule networks on the uptake and cytoplasmic transport of multicomponent cationic liposome-DNA complexes in CHO-K1 live cells by means of confocal laser scanning microscopy and 3D single particle tracking. Treatment with actin (latrunculin B)- and microtubule-disrupting (nocodazole) reagents indicated that intracellular trafficking of complexes predominantly involves microtubule-dependent active transport. We found that the actin network has a major effect on the initial uptake of complexes, while the microtubule network is mainly responsible for the subsequent active transportation to the lysosomes.

CONCLUSION

Collectively, a strategy to improve the efficiency of lipid gene vectors can be formulated. We could find a lipid formulation that allows the nanoparticles to avoid the microtubule pathway to lysosomes.

DNA delivery with hyperbranched polylysine: a comparative study with linear and dendritic polylysine

PEI and polylysine are among the most investigated synthetic polymeric carriers for DNA delivery. Apart from their practical use, these 2 classes of polymers are also of interest from a fundamental point of view as they both can be prepared in different architectures (linear and branched/dendritic) and in a wide range of molecular weights, which is attractive to establish basic structure-activity relationships. This manuscript reports the results of an extensive study on the influence of molecular weight and architecture of a library of polylysine variants that includes linear, dendritic and hyperbranched polylysine. Hyperbranched polylysine is a new polylysine-based carrier that is structurally related to dendritic polylysine but possesses a randomly branched structure. Hyperbranched polylysine is attractive as it can be prepared in a one-step process on a large scale. The performance of these 3 classes of polylysine analogs was evaluated by assessing eGFP and IgG production in transient gene expression experiments with CHO DG44 cells, which revealed that protein production generally increased with increasing molecular weight and that at comparable molecular weight, the hyperbranched analogs were superior as compared to the dendritic and linear polylysines. To understand the differences between the gene delivery properties of the hyperbranched polylysine analogs on the one hand and the dendritic and linear polylysines on the other hand, the uptake and trafficking of the corresponding polyplexes were investigated. These experiments allowed us to identify (i) polyplex-external cell membrane binding, (ii) free, unbound polylysine coexisting with polyplexes as well as (iii) polymer buffer capacity as three possible factors that may contribute to the superior transfection properties of the hyperbranched polylysines as compared to their linear and dendritic analogs. Altogether, the results of this study indicate that hyperbranched polylysine is an interesting, alternative synthetic gene carrier. Hyperbranched polylysine can be produced at low costs and in large quantities, is partially biodegradable, which may help to prevent cumulative cytotoxicity, and possesses transfection properties that can approach those of PEI.

Surface functionality of nanoparticles determines cellular uptake mechanisms in mammalian cells

Nanoparticles (NPs) are versatile scaffolds for numerous biomedical applications including drug delivery and bioimaging. The surface functionality of NPs essentially dictates intracellular NP uptake and controls their therapeutic action. Using several pharmacological inhibitors, it is demonstrated that the cellular uptake mechanisms of cationic gold NPs in both cancer (HeLa) and normal cells (MCF10A) strongly depend on the NP surface monolayer, and mostly involve caveolae and dynamin-dependent pathways as well as specific cell surface receptors (scavenger receptors). Moreover, these NPs show different uptake mechanisms in cancer and normal cells, providing an opportunity to develop NPs with improved selectivity for delivery applications.

Inhaled chemotherapy in lung cancer: future concept of nanomedicine

Regional chemotherapy was first used for lung cancer 30 years ago. Since then, new methods of drug delivery and pharmaceuticals have been investigated in vitro, and in animals and humans. An extensive review of drug delivery systems, pharmaceuticals, patient monitoring, methods of enhancing inhaled drug deposition, safety and efficacy, and also additional applications of inhaled chemotherapy and its advantages and disadvantages are presented. Regional chemotherapy to the lung parenchyma for lung cancer is feasible and efficient. Safety depends on the chemotherapy agent delivered to the lungs and is dose-dependent and time-dependent. Further evaluation is needed to provide data regarding early lung cancer stages, and whether regional chemotherapy can be used as neoadjuvant or adjuvant treatment. Finally, inhaled chemotherapy could one day be administered at home with fewer systemic adverse effects.

Nucleic-acid based gene therapeutics: delivery challenges and modular design of nonviral gene carriers and expression cassettes to overcome intracellular barriers for sustained targeted expression

The delivery of nucleic acid molecules into cells to alter physiological functions at the genetic level is a powerful approach to treat a wide range of inherited and acquired disorders. Biocompatible materials such as cationic polymers, lipids, and peptides are being explored as safer alternatives to viral gene carriers. However, the comparatively low efficiency of nonviral carriers currently hampers their translation into clinical settings. Controlling the size and stability of carrier/nucleic acid complexes is one of the primary hurdles as the physicochemical properties of the complexes can define the uptake pathways, which dictate intracellular routing, endosomal processing, and nucleocytoplasmic transport. In addition to nuclear import, subnuclear trafficking, posttranscriptional events, and immune responses can further limit transfection efficiency. Chemical moieties, reactive linkers or signal peptide have been conjugated to carriers to prevent aggregation, induce membrane destabilization and localize to subcellular compartments. Genetic elements can be inserted into the expression cassette to facilitate nuclear targeting, delimit expression to targeted tissue, and modulate transgene expression. The modular option afforded by both gene carriers and expression cassettes provides a two-tier multicomponent delivery system that can be optimized for targeted gene delivery in a variety of settings.

Monolayer coated gold nanoparticles for delivery applications

Gold nanoparticles (AuNPs) provide attractive vehicles for delivery of drugs, genetic materials, proteins, and small molecules. AuNPs feature low core toxicity coupled with the ability to parametrically control particle size and surface properties. In this review, we focus on engineering of the AuNP surface monolayer, highlighting recent advances in tuning monolayer structures for efficient delivery of drugs and biomolecules. This review covers two broad categories of particle functionalization, organic monolayers and biomolecule coatings, and discusses their applications in drug, DNA/RNA, protein and small molecule delivery.

DNA cage delivery to mammalian cells

DNA cages are nanometer-scale polyhedral structures formed by self-assembly from synthetic DNA oligonucleotides. Potential applications include in vivo imaging and the targeted delivery of macromolecules into living cells. We report an investigation of the ability of a model cage, a DNA tetrahedron, to enter live cultured mammalian cells. Cultured human embryonic kidney cells were treated with a range of fluorescently labeled DNA tetrahedra and subsequently examined using confocal microscopy and flow cytometry. Substantial uptake of tetrahedra into cells was observed both when the cells were treated with tetrahedra alone and when the cells were treated with a mixture of tetrahedra and a transfection reagent. Analysis of the subcellular localization of transfected tetrahedra using confocal microscopy and organelle staining indicates that the cages are located in the cytoplasm. FRET experiments indicate that the DNA cages remain substantially intact within the cells for at least 48 h after transfection. This is a first step toward the use of engineered DNA nanostructures to deliver and control the activity of cargoes within cells.

Protein kinase A inhibition modulates the intracellular routing of gene delivery vehicles in HeLa cells, leading to productive transfection

Cellular entry of nanoparticles for drug- and gene delivery relies on various endocytic pathways, including clathrin- and caveolae-mediated endocytosis. To improve delivery, i.e., the therapeutic and/or cell biological impact, current efforts are aimed at avoiding processing of the carriers along the degradative clathrin-mediated pathway towards lysosomes, and promoting that along the caveolae-mediated pathway. Here, we demonstrate the effective internalization of branched polyethylenimine polymers (BPEI), complexed with nucleic acids, by HeLa cells along both pathways. However, transfection efficiency or nuclear ODN delivery primarily occurs via the caveolae-mediated pathway, along which delivery into lysosomes is avoided. Interestingly, inhibition of intracellular protein kinase A (PKA) activity modulates the intracellular trafficking of both poly- and lipoplexes along the clathrin-mediated pathway by impeding trafficking into the late endosomal/lysosomal compartments, thus avoiding degradation. In case of BPEI polyplexes this promotes their transfection efficiency by 2-3 fold. Evidence excludes early endosomes as a major site for BPEI-mediated release/delivery. Rather, we identify a novel compartment, tentatively characterized as a transferrin(-)/rab9(-)/LAMP1(-) compartment, to which cargo within the clathrin-mediated pathway of endocytosis is rerouted upon inhibition of PKA, and which may act as an alternative and effective site of cargo release in gene delivery. Our findings offer new opportunities for improving gene delivery by non-viral based nanoparticles.

Paclitaxel tumor-priming enhances siRNA delivery and transfection in 3-dimensional tumor cultures

The clinical development of siRNA cancer therapeutics is limited by the poor interstitial transport and inefficient transfection in solid tumors. We have shown that paclitaxel pretreatment, by inducing apoptosis, causes expansion of the interstitial space and thereby improves nanoparticle delivery and transport in tumor interstitium (referred to as paclitaxel tumor priming) and efficacy of nanomedicines in tumor-bearing animals. The present study evaluated whether paclitaxel tumor priming improves the delivery and transfection of siRNA in 2- and 3-dimensional cultures of human oropharyngeal carcinoma FaDu cells. We used the fluorescent siGLO and confocal microcopy to monitor transport, and used survivin siRNA and immunostaining and immunoblotting to monitor transfection. Survivin is a chemoresistance gene/protein, inducible by chemotherapy. siRNA was loaded in cationic liposomes. The results showed that pretreatment with 50-200 nM paclitaxel (24 or 48 h before siRNA) enhanced the total uptake of siGLO into monolayers (∼15%, p < 0.05), and the depth of penetration into 3-dimensional spheroids and tumor fragment histocultures (2.1- to 2.5-times greater area under the penetration-depth curve). In both monolayer cells and histocultures, paclitaxel pretreatment induced survivin upregulation (p < 0.05). Survivin siRNA alone decreased the survivin levels in a dose-dependent manner, and applying survivin siRNA after paclitaxel pretreatment completely abolished the paclitaxel-induced survivin increases. These findings indicate that paclitaxel tumor priming did not compromise the siRNA functionality. In summary, paclitaxel tumor priming improved the penetration, transfection and functionality of siRNA in tumors, thus offering a promising and practical means to develop chemo-siRNA cancer gene therapy.

Particle tracking of intracellular trafficking of octaarginine-modified liposomes: a comparative study with adenovirus

It is previously reported that octaarginine (R8)-modified liposome (R8-Lip) was taken up via macropinocytosis, and subsequently delivered to the nuclear periphery. In the present study, we investigated the mechanism for the cytoplasmic transport of R8-Lips, comparing with that for adenovirus. Treatment with microtubule-disruption reagent (nocodazole) inhibited the transfection activity of plasmid DNA (pDNA)-encapsulating R8-Lip more extensively than that of adenovirus. The directional transport of R8-Lips along green fluorescent protein (GFP)-tagged microtubules was observed; however, the velocity was slower than those for adenovirus or endosomes that were devoid of R8-Lips. These directional motions were abrogated in R8-Lips by nocodazole treatment, whereas adenovirus continued to undergo random motion. This finding suggests that the nuclear access of R8-Lip predominantly involves microtubule-dependent transport, whereas an apparent diffusive motion is also operative in nuclear access of adenovirus. Furthermore, quantum dot-labeled pDNA underwent directional motion concomitantly with rhodamine-labeled lipid envelopes, indicating that the R8-Lips were subject to microtubule-dependent transport in the intact form. Dual particle tracking of carriers and endosomes revealed that R8-Lip was directionally transported, associated with endosomes, whereas this occurs after endosomal escape in adenovirus. Collectively, the findings reported herein indicate that vesicular transport is a key factor in the cytoplasmic transport of R8-Lips.

Fluorescence methods for evaluating lipoplex-mediated gene delivery

The biological activity of cationic liposome/DNA complexes ("lipoplexes") is strongly dependent on their ability to protect DNA and to interact with cells, including binding to the cell surface, internalization via endocytosis and cytoplasmic delivery of the DNA. In this chapter, we describe a number of methods and procedures to study these processes, based on the use of fluorescent probes.

Uptake mechanism of oppositely charged fluorescent nanoparticles in HeLa cells

The endocytotic mechanisms involved in the uptake of charged polystyrene nanoparticles into HeLa cells were investigated. Uptake experiments were done in the presence or absence of drugs known to inhibit various factors in endocytosis. Independent of the particle charge, endocytosis is highly dependent on dynamin, F-actin, and tyrosine-specific protein kinases, which suggests a dynamin-dependent and lipid raft-dependent mechanism. However, cholesterol depletion did not hinder particle uptake. Regarding positively charged particles, macropinocytosis, the microtubule network, and cyclooxygenases are also involved. The clathrin-dependent pathway plays a minor role.

The effect of nocodazole on the transfection efficiency of lipid-bilayer coated gold nanoparticles

Nonviral vectors are safer than viral systems for gene therapy applications. However, the limited efficacy always prevents their being widely used in clinical practice. Aside from searching new gene nonviral vectors, many researchers focus on finding out new substances to improve the transfection efficiency of existent vectors. In this work, we found a transfection enhancer, nocodazole (NCZ), for dimethyldioctadecylammonium (DODAB, a cationic lipid) bilayer coated gold nanoparticles (AuNPs) mediated gene delivery. It was found that NCZ produces 3-fold transfection enhancement to HEK 293T cells assessed by flow cytometry (FCM). The result was further confirmed by luciferase assay, in which NCZ induced more than 5 times improvement in transfection efficiency after 48 h of transfection. The results from the inductively coupled plasma mass spectrometry (ICP-MS) and FCM showed that NCZ did not affect the internalization of DODAB-AuNPs/DNA complexes. The trafficking of the complexes by transmission electron microscopy (TEM) indicated that the interrupted transportation of the complexes to the lysosomes contributed greatly to the transfection enhancement. Therefore, NCZ can be used as a transfection enhancer in DODAB-AuNPs mediated transfection system. This work also gave an insight to improving the efficiency of lipid-mediated transfection: modifying lipid on gold nanoparticles and pre-treating cells by NCZ before the transfection.

Biochemical investigation of active intracellular transport of polymeric gene-delivery vectors

To design safe, efficient synthetic gene therapy vectors, it is desirable to understand the intracellular mechanisms that facilitate their delivery from the cell surface to the nucleus. Elements of the cytoskeleton and molecular motor proteins are known to play a pivotal role in most intracellular active transport processes. The actin depolymerizer cytochalasin D and microtubule effectors colchicine and paclitaxel were used to evaluate the function of these components of the cytoskeleton in the trafficking of polyethylenimine (PEI)-DNA complexes. In addition, ATPase inhibitors erythro-9[3-(2-hydroxynonyl)] adenine (EHNA), vanadate, adenylylimidodiphosphate (AMP-PNP), and rose bengal lactone (RBL), which have inhibitory activity against dynein and kinesin, were used to examine to the effects of these molecular motors on PEI-DNA delivery. Disruption of microfilaments decreased the delivery efficiency of PEI polyplexes 60-80%, though cytochalasin D did not significantly inhibit uptake. Depolymerization of microtubules by colchicine decreased transfection efficiency by 75%. Microtubule stabilization with paclitaxel, however, facilitated a 20-fold increase in gene expression. Treatment with EHNA and vanadate caused 50% and 80% decreases in transfection efficiency, respectively. Transfection efficiency was also decreased by RBL (80%) and AMP-PNP (98%). Our findings confirm the importance of microfilament- and microtubule-based active transport of PEI-DNA complexes. Further, the strong decrease in transfection efficiency caused by ATPase inhibitors that possess inhibitory activity against kinesin implies an unexpected role for these motors in gene delivery.

Fc receptor-mediated, antibody-dependent enhancement of bacteriophage lambda-mediated gene transfer in mammalian cells

Lambda phage vectors mediate gene transfer in cultured mammalian cells and in live mice, and in vivo phage-mediated gene expression is increased when mice are pre-immunized with bacteriophage lambda. We now show that, like eukaryotic viruses, bacteriophage vectors are subject to Fc receptor-mediated, antibody-dependent enhancement of infection in mammalian cells. Antibody-dependent enhancement of phage gene transfer required FcgammaRI, but not its associated gamma-chain, and was not supported by other FcgammaR family members (FcgammaRIIA, FcgammaRIIB, and FcgammaRIII). Studies using chlorpromazine and latrunculin A revealed an important role for clathrin-mediated endocytosis (chlorpromazine) and actin filaments (latrunculin A) in antibody-enhanced phage gene transfer. This was confirmed by experiments using inhibitors of endosomal acidification (bafilomycin A1, monensin) and by immunocytochemical colocalization of internalized phage particles with early endosome-associated protein-1 (EAA1). In contrast, microtubule-targeting agents (nocodazole, taxol) increased the efficiency of antibody-enhanced phage gene transfer. These results reveal an unexpected antibody-dependent, FcgammaRI-mediated enhancement of phage transduction in mammalian cells, and suggest new approaches to improve bacteriophage-mediated gene transfer.

Synergistic antitumoral effect of vinblastine and HSV-Tk/GCV gene therapy mediated by albumin-associated cationic liposomes

Despite recent advances in conventional therapeutic approaches for cancer, the frequently observed acquired drug resistance and toxic side effects have limited their clinical application. The main goal of this work was to investigate the combined antitumoral effect of vinblastine with HSV-Tk/GCV "suicide" gene therapy mediated by human serum albumin (HSA)-associated lipoplexes, in mammary adenocarcinoma cells (TSA cells). Our results show that, among the different lipoplex formulations tested, HSA-associated complexes prepared from EPOPC:Chol liposomes, at the (4/1) (+/-) charge ratio, was the most efficient to mediate gene delivery, even in the presence of serum. The simultaneous addition of vinblastine and HSA-EPOPC:Chol/DNA (+/-) (4/1) lipoplexes to TSA cells improved transgene expression more than 10 times. When combined with the HSV-Tk/GCV "suicide" gene therapy mediated by HSA-EPOPC:Chol/DNA (+/-) (4/1) lipoplexes, vinblastine induced a great enhancement in the antitumoral activity in TSA cells. Most importantly, this combined strategy resulted in a significant synergistic effect, thus allowing the use of a much lower dose of the drug to achieve the same therapeutic effect. Overall, our results indicate that this approach has the potential to overcome some major limitations of conventional chemotherapy, and may therefore constitute a promising strategy for future applications in antitumoral therapy.

Effect of the hydrocarbon chain and polymethylene spacer lengths on gene transfection efficacies of gemini lipids based on aromatic backbone

Design, syntheses, and gene delivery efficacies of fifteen novel gemini (dimeric) and three monomeric cationic lipids anchored on an aromatic backbone have been described. Each new lipid has been used for liposome formation, and optimal formulations were used to determine the structure-activity correlation of the gene transfection efficacies of these lipids in HeLa and HT1080 cells. The results of the present investigation bring out the effect of hydrocarbon chain lengths and the length of the spacer between the headgroups on gene transfection efficiencies of the cationic gemini lipids based on aromatic backbone. The lipids bearing n-C 14H 29 hydrocarbon chain lengths have been found to be the best transfecting agents compared to their counterparts with n-C 16H 33 and n-C 12H 25 chains in HeLa cells. On the other hand, in HT1080 cells, the lipids based on n-C 12H 25 and n-C 14H 29 chains were found to be more potent transfecting agents than lipids possessing n-C 16H 33 chains. Transmission electron microscopy examination revealed the existence of spherical lipid-DNA complexes.

Cytoskeletal involvement in the cellular trafficking of plasmid/PEI derivative complexes

We have studied the cytoskeletal involvement in the cellular trafficking of complexes made with plasmid/PEI or plasmid/lactosylated PEI in cystic fibrosis airway epithelial cells (SigmaCFTE29o- cells). Complexes were incubated in the presence of cytoskeletal inhibitors, and the number of transfected cells was determined by flow cytometry. Complexes were also generated with fluorescein-labeled PEI derivatives and the cell fluorescence intensity was determined by flow cytometry. In the presence of cytochalasin D to depolymerize actin filaments or nocodazole to disrupt microtubules, gene transfer efficiency with both PEI derivatives was decreased by 90%. The uptake of fluoresceinylated complexes studied by flow cytometry was decreased by 50% in the presence of cytochalasin D for both types of complexes (p<0.005) and unchanged in the presence of nocodazole. When cytoskeletal inhibitors were added to the cell culture after the complex uptake had occurred, gene transfer efficiency was decreased by 75% and 50% in the presence of nocodazole and cytochalasin D, respectively. Upon nocodazole-microtubule network disruption, the lysosomal localization of complexes was reduced, as assessed by confocal microscopy. Our results show a major cytoskeletal involvement in the cellular trafficking of complexes made with both PEI derivatives: actin filaments mainly in complex uptake, and microtubules in the trafficking of complexes towards the nucleus, probably through guided transport of complex-containing endosomal vesicles.

NBD-conjugated biosurfactant (MEL-A) shows a new pathway for transfection

Gene transfection is a fundamental technology for molecular and cell biology, and also clinical gene therapy. A variety of non-viral vectors have been investigated for gene transfection, but their gene delivery had remained an inefficient process. Recently, we found that a biosurfactant, mannosylerythritol lipid (MEL)-A, dramatically increased the efficiency in transfection of plasmid DNA mediated by cationic liposomes. However, its mechanism has not been understood yet. Here we examined the mechanism of the transfection mediated by cationic liposomes with NBD-conjugated MEL-A. We found that MEL-A first gradually distributed on the intracellular membranes through the plasma membranes of target cells, while the cationic liposomes with MEL-A fused to the plasma membranes in 20-35 min. Thereafter, the oligonucleotide released from the vesicles was immediately transferred to the nucleus. The present results showed a new role of non-viral vectors in transfection.

Anchoring Cationic Amphiphiles for Nucleotide Delivery Significance of DNA Release from Cationic Liposomes for Transfection

We have designed and synthesized lithocholic acid-based cationic amphiphile molecules as components of cationic liposomes for gene transfection (lipofection). To study the relationship between the molecular structures of those amphiphilic molecules, particularly the extended hydrophobic appendant (anchor) at the 3-hydroxyl group, and transfection efficiency, we synthesized several lithocholic and isolithocholic acid derivatives, and examined their transfection efficiency. We also compared the physico-chemical properties of cationic liposomes prepared from these derivatives. We found that isolithocholic acid derivatives exhibit higher transfection efficiency than the corresponding lithocholic acid derivatives. This result indicates that the orientation and extension of hydrophobic regions influence the gene transfection process. Isolithocholic acid derivatives showed a high ability to encapsulate DNA in a compact liposome-DNA complex and to protect it from enzymatic degradation. Isolithocholic acid derivatives also facilitated the release of DNA from the liposome-DNA complex, which is a crucial step for DNA entry into the nucleus. Our results show that the transfection efficiency is directly influenced by the ability of the liposome complex to release DNA, rather than by the DNA-encapsulating ability. Molecular modeling revealed that isolithocholic acid derivatives take relatively extended conformations, while the lithocholic acid derivatives take folded structures. Thus, the efficiency of release of DNA from cationic liposomes in the cytoplasm, which contributes to high transfection efficiency, appears to be dependent upon the molecular shape of the cationic amphiphiles.

[Functional fluctuation]

The discovery of the double-helical structure of DNA, the elucidation of the genetic code, and the determination of the three-dimensional structure of several proteins are some of the outstanding achievements of biochemistry and life sciences in the latter half of the last century. Proteins play key roles in almost all the biological processes and the biological function of a protein depends on its conformation which is defined as the three-dimensional arrangement of the atoms of a molecule. The three-dimensional structure, however, is not rigid but fluctuated. Structural fluctuation plays an important role in bio-macromolecules. How about "functional fluctuation" in biological systems? The present review proposes that functional fluctuation is also very important for understanding the mechanism of supramolecules, biological processes in living cells, and the interaction between biological systems. This new theme is pretty well supported by our recent experiments for neuro-immune crosstalk, gene transfection with cationic liposomes, and cell signaling in embryonic stem cells.

Intracellular trafficking of nonviral vectors

Nonviral vectors continue to be attractive alternatives to viruses due to their low toxicity and immunogenicity, lack of pathogenicity, and ease of pharmacologic production. However, nonviral vectors also continue to suffer from relatively low levels of gene transfer compared to viruses, thus the drive to improve these vectors continues. Many studies on vector-cell interactions have reported that nonviral vectors bind and enter cells efficiently, but yield low gene expression, thus directing our attention to the intracellular trafficking of these vectors to understand where the obstacles occur. Here, we will review nonviral vector trafficking pathways, which will be considered here as the steps from cell binding to nuclear delivery. Studies on the intracellular trafficking of nonviral vectors has given us valuable insights into the barriers these vectors must overcome to mediate efficient gene transfer. Importantly, we will highlight the different approaches used by researchers to overcome certain trafficking barriers to gene transfer, many of which incorporate components from biological systems that have naturally evolved the capacity to overcome such obstacles. The tools used to study trafficking pathways will also be discussed.

The functional cooperation of MAP1A heavy chain and light chain 2 in the binding of microtubules

Microtubule-associated protein 1A (MAP1A) is a high-molecular-weight protein that is comprised of a heavy chain and a light chain (LC2) and is widely distributed along the microtubules in both mature neurons and glial cells. To illustrate the interaction among the MAP1A heavy chain, light chain, and microtubule, we prepared DNA constructs with Myc-, EGFP-, or DsRed-tags for full-length MAP1A DNA expressing whole MAP1A protein, two domains of MAP1A heavy chain, and light chain. Distribution patterns of various MAP1A domains as well as their interactions with microtubules were monitored in a non-neuronal COS7 and a neuronal Neuro2A cells. Our data revealed that a complete MAP1A protein, which contains both heavy chain and LC2, could be colocalized with microtubule networks not only in Neuro2A cells but also in transfected COS7 cells. Filamentous structures failed to be visualized along microtubules in COS7 cells transfected with MAP1A heavy chain or LC2 alone. Whereas, after introducing MAP1A heavy chain with LC2 into COS7 cells, both heavy chain and LC2 could be colocalized with microtubules. From our functional analysis, both MAP1A and its LC2 could protect microtubules against the challenge of nacodazol. Data collected from yeast two-hybrid assays of various MAP1A domains confirmed that the interaction of LC2 and NH2-terminal of MAP1A heavy chain is important for microtubule binding. From our analysis of MAP1A functional domains, we suggest that interactions between MAP1A heavy chain and LC2 are critical for the binding of microtubules.

Quantitating intracellular transport of polyplexes by spatio-temporal image correlation spectroscopy

Quantitatively understanding how nonviral gene delivery vectors (polyplexes) are transported inside cells is essential before they can be optimized for gene therapy and medical applications. In this study, we used spatio-temporal image correlation spectroscopy (ICS) to follow polymer-nucleic acid particles (polyplexes) of various sizes and analyze their diffusive-like and flow behaviors intracellularly to elucidate the mechanisms responsible for their transport. ICS is a quantitative imaging technique that allows the assessment of particle motion in complex systems, although it has not been widely used to date. We find that the internalized polyplexes are able to use microtubule motors for intracellular trafficking and exhibit different transport behaviors for short (<10 s) versus long (approximately 60 s) correlation times. This motion can be explained by a memory effect of the microtubule motors. These results reveal that, although microtubule motor biases may be present for short periods of time, resulting in a net directional velocity, the overall long-term motion of the polyplexes is best described as a random walk-like process. These studies suggest that spatio-temporal ICS is a powerful technique for assessing the nature of intracellular motion and provides a quantitative tool to compare the transport of different objects within a living cell.

Carrier-based strategies for targeting protein and peptide drugs to the lungs

With greater interest in delivery of protein and peptide-based drugs to the lungs for topical and systemic activity, a range of new devices and formulations are being investigated. While a great deal of recent research has focused on the development of novel devices, attention must now be paid to the formulation of these macromolecular drugs. The emphasis in this review will be on targeting of protein/peptide drugs by inhalation using carriers and ligands.