Low-generation asymmetric dendrimers exhibit minimal toxicity and effectively complex DNA

Conventional dendrimers are spherical symmetrically branched polymers ending with active surface functional groups. Polyamidoamine (PAMAM) dendrimers have been widely studied as gene delivery vectors and have proven effective at delivering DNA to cells in vitro. However, higher-generation (G4-G8) PAMAM dendrimers exhibit toxicity due to their high cationic charge density and this has limited their application in vitro and in vivo. Another limitation arises when attempts are made to functionalize spherical dendrimers as targeting moieties cannot be site-specifically attached. Therefore, we propose that lower-generation asymmetric dendrimers, which are likely devoid of toxicity and to which site-specific attachment of targeting ligands can be achieved, would be a viable alternative to currently available dendrimers. We synthesized and characterized a series of peptide-based asymmetric dendrimers and compared their toxicity profile and ability to condense DNA to spherical PAMAM G1 dendrimers. We show that asymmetric dendrimers are minimally toxic and condense DNA into stable toroids which have been reported necessary for efficient cell transfection. This paves the way for these systems to be conjugated with targeting ligands for gene delivery in vitro and in vivo. Copyright (C) 2011 European Peptide Society and John Wiley & Sons, Ltd

A new dawn for the use of traditional Chinese medicine in cancer therapy

Although traditional Chinese medicine has benefitted one fifth of the world's population in treating a plethora of diseases, its acceptance as a real therapeutic option by the West is only now emerging. In light of a new wave of recognition being given to traditional Chinese medicine by health professionals and regulatory bodies in the West, an understanding of their molecular basis and highlighting potential future applications of a proven group of traditional Chinese medicine in the treatment of a variety of cancers is crucial – this is where their calling holds much hope and promise in both animal and human trials. Furthermore, the rationale for combining conventional agents and modern biotechnological approaches to the delivery of traditional Chinese medicine is an avenue set to revolutionize the future practice of cancer medicine – and this may well bring on a new dawn of therapeutic strategies where East truly meets West

Particle size- and number-dependent delivery to cells by layered double hydroxide nanoparticles

It is well known that delivery efficiency to cells is highly dependent on particle size and the administered dose. However, there is a marked discrepancy in many reports, mainly due to the inconsistency in assessment of various parameters. In this particular research, we designed experiments using layered double hydroxide nanoparticles (LDH NPs) to specifically elucidate the effect of particle size, dose and dye loading manner on cellular uptake. Using the number of LDH NPs taken up by HCT-116 cells as the indicator of delivery efficiency, we found that (1) the size of sheet-like LDH in the range of 40–100 nm did not significantly affect their cellular uptake; (2) cellular uptake of 40 and 100 nm LDH NPs was increased proportionally to the number concentration below a critical value, but remained relatively constant beyond the critical value; and (3) the effect of the dye loading manner is mainly dependent on the loading capacity or yield. In particular, the loading capacity is determined by the NP specific surface area. This research may be extended to a larger size range to examine the size effect, but suggests that it is necessary to set up a protocol to evaluate the effects of NP’s physicochemical properties on the cellular delivery efficiency

Cell Membrane Penetration without Pore Formation : Chameleonic Properties of Dendrimers in Response to Hydrophobic and Hydrophilic Environments

The mechanism by which cell-penetrating peptides and antimicrobial peptides cross plasma membranes is unknown, as is how cell-penetrating peptides facilitate drug delivery, mediating the transport of small molecules. Once nondisruptive and nonendocytotic pathways are excluded, pore formation is one of the proposed mechanisms, including toroidal, barrel-stave, or carpet models. Spontaneous pores are observed in coarse-grained simulations and less often in molecular dynamics simulations. While pores are widely assumed and inferred, there is no unambiguous experimental evidence of the existence of pores. Some recent experimental studies contradict the mechanistic picture of pore formation, however, highlighting the possibility of a direct translocation pathway that is both nondisruptive and nonendocytotic. In this work, a model is proposed a model for peptide (linear and dendritic) translocation which does not require the presence of pores and which potentially accords with such experiments. It is suggested that a charged peptide, as it experiences an increasingly hydrophobic environment within the membrane surface, can utilize a proton chain transfer mechanism to shed its protons to counter ions or potentially phospholipid head groups in the membrane skin region, thereby becoming compatible with the hydrophobic interior of the membrane. This increases the likelihood to move into the highly hydrophobic core of the membrane and ultimately reach the opposite leaflet to re-acquire protons again, suggesting a potential "chameleon" mechanism for non-disruptive and non-endocytotic membrane translocation. The molecular dynamics simulations reveal stability of peptide bridges joining two membrane leaflets and demonstrate that this can facilitate cross-membrane transport of small drug molecules.Peer reviewe

Engineering small MgAl-layered double hydroxide nanoparticles for enhanced gene delivery

In this paper we report an approach for engineering small MgAl-layered double hydroxide (sLDH) nanoparticles with the Z-average diameter of about 40 nm. This method first requires co-precipitation of magnesium and aluminum nitrate solution with sodium hydroxide in methanol, followed by LDH slurry collection and re-suspension in methanol. The methanol suspension is then heated in an autoclave, followed by separation via centrifugation and thorough washing with deionized water. The nanoparticles are finally dispersed in deionized water into homogeneous aqueous suspension after 4–6 day standing at room temperature. In general, sLDH nanoparticles have the Z-average size of 35–50 nm, the number-average size of 14–30 nm and the polydispersity index (PdI) of 0.19–0.25. The prepared sLDH suspension is stable for at least 1 month when stored at fridge (2–8 °C) or ambient (22–25 °C) temperature. Moreover, sLDH nanoparticles are found to carry higher payloads of small double stranded DNA (dsDNA). More excitedly, sLDH nanoparticles transfect dsDNA into HEK 293T cells with a 5 to 6-fold greater efficiency compared to the larger LDH particles (Z-average diameter of 110 nm)

Influence of peptide dendrimers and sonophoresis on the transdermal delivery of ketoprofen

The aim of this study was to determine the individual and combined effects of peptide dendrimers and low frequency ultrasound on the transdermal permeation of ketoprofen. Arginine terminated peptide dendrimers of varying charges (4(+), 8(+) and 16(+), named as A4. A8 and A16 respectively) were synthesized and characterized. Ketoprofen was subjected to passive, peptide dendrimer-assisted and sonophoretic permeation studies (with and without dendrimer application) across Swiss albino mouse skin, both in vitro and in vivo. The studies revealed that the synthesized peptide dendrimers considerably increased the transdermal permeation of ketoprofen and displayed enhancement ratios of up to 3.25 (with A16 dendrimer), compared to passive diffusion of drug alone in vitro. Moreover, the combination of peptide dendrimer treatment and ultrasound application worked in synergy and gave enhancement ratios of up to 1369.15 (with ketoprofen-A16 dendrimer complex). In vivo studies demonstrated that dendrimer and ultrasound-assisted permeation of drug achieved much higher plasma concentration of drug, compared to passive diffusion. Comparison of transdermal and oral absorption studies revealed that transdermal administration of ketoprofen with A8 dendrimer showed comparable absorption and plasma drug levels with oral route. The excised mouse skin after in vivo permeation study with dendrimers and ultrasound did not show major toxic reactions. This study demonstrates that arginine terminated peptide dendrimers combined with sonophoresis can effectively improve the transdermal permeation of ketoprofen. (C) 2017 Elsevier B.V. All rights reserved

Peptide dendrimer-conjugates of ketoprofen: synthesis and ex vivo and in vivo evaluations of passive diffusion, sonophoresis and iontophoresis for skin delivery

The aim of this study was to evaluate skin delivery of ketoprofen when covalently tethered to mildly cationic (2or 4) peptide dendrimers prepared wholly by solid phase peptide synthesis. The amino acids glycine, arginine and lysine formed the dendrimer with ketoprofen tethered either to the lysine side-arm (N) or periphery of dendrimeric branches. Passive diffusion, sonophoresis- and iontophoresis-assisted permeation of each peptide dendrimer-drug conjugate (D1–D4) was studied across mouse skin, both in vitro and in vivo. In addition, skin toxicity of dendrimeric conjugates when trialed with iontophoresis or sonophoresis was also evaluated. All dendrimeric conjugates improved aqueous solubility at least 5-fold, compared to ketoprofen alone, while also exhibiting appreciable lipophilicity. In vitro passive diffusion studies revealed that ketoprofen in its native form was delivered to a greater extent, compared with a dendrimer-conjugated form at the end of 24\ua0h (Q(μg/cm): ketoprofen (68.06\ua0±\ua03.62)\ua0>\ua0D2 (49.62\ua0±\ua02.92)\ua0>\ua0D4 (19.20\ua0±\ua00.89)\ua0>\ua0D1 (6.45\ua0±\ua00.40)\ua0>\ua0D3 (2.21\ua0±\ua00.19). However, sonophoresis substantially increased the skin permeation of ketoprofen-dendrimer conjugates in 30\ua0min (Q(μg/cm): D4 (122.19\ua0±\ua07.14)\ua0>\ua0D2 (66.74\ua0±\ua03.86)\ua0>\ua0D1 (52.10\ua0±\ua03.22)\ua0>\ua0D3 (41.66\ua0±\ua03.22)) although ketoprofen alone again proved superior (Q: 167.99\ua0±\ua09.11\ua0μg/cm). Next, application of iontophoresis was trialed and shown to considerably increase permeation of dendrimeric ketoprofen in 6\ua0h (Q(μg/cm): D2 (711.49\ua0±\ua039.14)\ua0>\ua0D4 (341.23\ua0±\ua016.43)\ua0>\ua0D3 (89.50\ua0±\ua04.99)\ua0>\ua0D1 (50.91\ua0±\ua02.98), with a Qvalue of 96.60\ua0±\ua05.12\ua0μg/cmfor ketoprofen alone). In vivo studies indicated that therapeutically relevant concentrations of ketoprofen could be delivered transdermally when iontophoresis was paired with D2 (985.49\ua0±\ua043.25\ua0ng/mL). Further, histopathological analysis showed that the dendrimeric approach was a safe mode as ketoprofen alone. The present study successfully demonstrates that peptide dendrimer conjugates of ketoprofen, when combined with non-invasive modalities, such as iontophoresis can enhance skin permeation with clinically relevant concentrations achieved transdermally

Flexibility of short-strand RNA in aqueous solution as revealed by molecular dynamics simulation:are A′-RNA and A-RNA distinct conformational structures?

We use molecular dynamics simulations to compare the conformational structure and dynamics of a 21-base pair RNA sequence initially constructed according to the canonical A-RNA and A'-RNA forms in the presence of counterions and explicit water. Our study aims to add a dynamical perspective to the solid-state structural information that has been derived from X-ray data for these two characteristic forms of RNA. Analysis of the three main structural descriptors commonly used to differentiate between the two forms of RNA namely major groove width, inclination and the number of base pairs in a helical twist over a 30 ns simulation period reveals a flexible structure in aqueous solution with fluctuations in the values of these structural parameters encompassing the range between the two crystal forms and more. This provides evidence to suggest that the identification of distinct A-RNA and A'-RNA structures, while relevant in the crystalline form, may not be generally relevant in the context of RNA in the aqueous phase. The apparent structural flexibility observed in our simulations is likely to bear ramifications for the interactions of RNA with biological molecules (e.g. proteins) and non-biological molecules (e.g. non-viral gene delivery vectors)

A new dawn for the use of traditional Chinese medicine in cancer therapy

Reports of therapeutic success with traditional Chinese medicine (TCM) have until very recently been met with much scepticism and pessimism by the West, due in-part to the sheer lack of available credible and rigorous clinical data and at claims that a given TCM can remedy common ailments and be just as efficacious in eliminating life threatening diseases, such as cancer. The tide is now beginning to turn on this negative outlook, aided by the ever-increasing migration of people and along with them knowledge (based upon ancestral cultural influences) from two of the world’s fasting growing populations, China and India, to the West [1]. This translation to the West of ancient complementary and alternative medicine formularies and their ever-increasing integrative role in the armoury against cancer means that their presence and place in modern medicine can no longer be overlooked, by regulatory authorities and clinicians alike, as being merely anecdotal