Generation PAMAM Research Articles

PAMAM-Calix-Dendrimers: Third Generation Synthesis and Impact of Generation and Macrocyclic Core Conformation on Hemotoxicity and Calf Thymus DNA Binding

Background/Objectives: Current promising treatments for many diseases are based on the use of therapeutic nucleic acids, including DNA. However, the list of nanocarriers is limited due to their low biocompatibility, high cost, and toxicity. The design of synthetic building blocks for creating universal delivery systems for genetic material is an unsolved problem. In this work, we propose PAMAM dendrimers with rigid thiacalixarene core in various conformations, i.e., PAMAM-calix-dendrimers, as a platform for a supramolecular universal constructor for nanomedicine. Results: Third generation PAMAM dendrimers with a macrocyclic core in three conformations (cone, partial cone, and 1,3-alternate) were synthesized for the first time. The obtained dendrimers were capable of binding and compacting calf thymus DNA, whereby the binding efficiency improved with increasing generation, while the influence of the macrocyclic core was reduced. A dramatic effect of the macrocyclic core conformation on the hemolytic activity of PAMAM-calix-dendrimers was observed. Specifically, a notable reduction in hemotoxicity was associated with a decrease in compound amphiphilicity. Conclusions: We hope the results will help reduce financial and labor costs in developing new drug delivery systems based on dendrimers.

Enhanced plant-derived vesicles for nucleotide delivery for cancer therapy

Small RNAs (microRNAs [miRNAs] or small interfering RNAs [siRNAs]) are effective tools for cancer therapy, but many of the existing carriers for their delivery are limited by low bioavailability, insufficient loading, impaired transport across biological barriers, and low delivery into the tumor microenvironment. Extracellular vesicle (EV)–based communication in mammalian and plant systems is important for many physiological and pathological processes, and EVs show promise as carriers for RNA interference molecules. However, some fundamental issues limit their use, such as insufficient cargo loading and low potential for scaling production. Plant-derived vesicles (PDVs) are membrane-coated vesicles released in the apoplastic fluid of plants that contain biomolecules that play a role in several biological mechanisms. Here, we developed an alternative approach to deliver miRNA for cancer therapy using PDVs. We isolated vesicles from watermelon and formulated a hybrid, exosomal, polymeric system in which PDVs were combined with a dendrimer bound to miRNA146 mimic. Third generation PAMAM was chosen due to its high branching structure and versatility for loading molecules of interest. We performed several in vivo experiments to demonstrate the therapeutic efficacy of our compound and explored in vitro biological mechanisms underlying the anti-tumor effects of miRNA146, which are mostly related to its anti-angiogenic activity.

Second-Generation Polyamidoamine Dendrimer Conjugated with Oligopeptides Can Enhance Plasmid DNA Delivery In Vitro.

Poly(amidoamine) (PAMAM) dendrimers have attracted considerable attention in the field of gene therapy due to their flexibility in introducing different functional moieties and reduced toxicity at low generations. However, their transfection efficiency remains a limitation. Therefore, an essential approach for improving their transfection efficiency as gene carriers involves modifying the structure of PAMAM by conjugating functional groups around their surface. In this study, we successfully conjugated an RRHRH oligopeptide to the surface of PAMAM generation 2 (PAMAM G2) to create RRHRH-PAMAM G2. This construction aims to condense plasmid DNA (pDNA) and facilitate its penetration into cell membranes, leading to its promising potential for gene therapy. RRHRH-PAMAM G2/pDNA complexes were smaller than 100 nm and positively charged. Nano-polyplexes can enter the cell and show a high transfection efficiency after 24 h of transfection. The RRHRH-PAMAM G2 was non-toxic to HeLa, NIH3T3, A549, and MDA-MB-231 cell lines. These results strongly suggest that RRHRH-PAMAM G2 holds promise as a gene carrier for gene therapy owing to its biocompatibility and ability to deliver genes to the cell.

Intramacromolecular Conformational Changes in Low Generation PAMAM Dendrimers Probed by Pyrene Excimer Formation.

Pyrene excimer formation (PEF) was used to probe the intramacromolecular conformational change experienced by low generation pyrene-labeled PAMAM dendrimers referred to as PyCX-PAMAM-GY, where X (=4, 8, or 12) and Y (=0, 1, or 2) represent the number of atoms in the pyrenyl linker and the dendrimer generation, respectively. Each sample was studied in N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) with and without 5 mM HCl. Global analysis of the monomer and excimer time-resolved fluorescence decays using the model free analysis (MFA) yielded the average rate constant of excimer formation, ⟨k⟩, which was compared with the local pyrene concentration ([Py]loc) of the PyCX-PAMAM-GY samples calculated by assuming that the oligomeric segments constituting the dendrimer's interior obeyed Gaussian statistics. A notable decrease in ⟨k⟩ was observed upon the addition of 5 mM HCl to the PyCX-PAMAM-GY solutions and was attributed to swelling of the dendrimers resulting from the protonation of the internal tertiary amines. The reversibility of this conformational change could also be monitored via PEF. Solvent differences between DMF and DMSO were accounted for by dividing ⟨k⟩ by kdiff, the bimolecular rate constant for diffusive PEF of a n-hexyl-1-pyrenebutyramide model compound, to yield the ⟨k⟩/kdiff ratio. Comparison between the ⟨k⟩/kdiff ratios obtained for all the PyCX-PAMAM-GY samples with and without 5 mM HCl revealed a 13% increase in the radius of the PAMAM-GY dendrimers upon protonation of their internal tertiary amines in agreement with earlier reports. These experiments illustrate that PEF represents a powerful experimental means to quantitatively probe the intramacromolecular conformational changes of complex macromolecules in solution, in a manner that complements scattering techniques.

Influence of the Chemical Structure on the Mechanical Relaxation of Dendrimers.

The rheological properties of macromolecules represent one of the fundamental features of polymer systems which expand the possibilities of using and developing new materials based on them. In this work, we studied the shear-stress relaxation of the second generation PAMAM and PPI dendrimer melts by atomistic molecular dynamics simulation. The time dependences of relaxation modulus G(t) and the frequency dependences of the storage G'(ω) and loss G″(ω) moduli were obtained. The results were compared with the similar dependences for the polycarbosilane (PCS) dendrimer of the same generation. The chemical structure of the dendrimer segments has been found to strongly influence their mechanical relaxation. In particular, it has been shown that hydrogen bonding in PAMAM dendrimers leads to an entanglement of macromolecules and the region is observed where G'(ω) > G″(ω). This slows down the mechanical relaxation and rotational diffusion of macromolecules. We believe that our comprehensive research contributes to the systematization of knowledge about the rheological properties of dendrimers.

Poly(amidoamine) dendrimer-induced 3D crosslinked network constructed on polyphenylene sulfide nonwoven as a battery separator: Effect of generation number on cell performance

High power lithium-ion batteries put forward challenges for separator in terms of meeting high current density, safety as well as superior cycling stability. In this study, Poly(amidoamine) (PAMAM) dendrimer-introduced three-dimensional (3D) crosslinked coating layer is built on polyphenylene sulfide (PPS) nonwoven substrate to address above issues and the generation number effect are discussed thoroughly. Due to unique advantages of PAMAM dendrimer including its hydrophilicity to electrolyte, embedding effect of internal cavities, and spherical steric structure, the porosity, ionic conductivity, interfacial compatible as well as lithium-ion transference number are improved for the crosslinked composite separator especially at higher generation number, which endow battery with superior discharge capacity of 162.5 mAh g−1 at 0.2 C and outstanding C-rate capabilities. Moreover, through the adjustment of generation number, less crosslinking junctions but more crosslinking points at one junction can be achieved in PAMAM-induced 3D crosslinked structures, thus leading to the improvement of all mechanical properties concurrently. This behavior can shift the oxidative decomposition potential to 5.36 V and give superior cell performance retention (98.6%) even after 100 cycles for battery using the fourth generation PAMAM. Therefore, this study will provide a new route for separator when pursuing higher rate performance and cyclic stability.

The Adsorption of Heavy Metal Ions by Poly (Amidoamine) Dendrimer-Functionalized Nanomaterials: A Review.

Rapid industrialization has resulted in serious heavy metal pollution. The removal of heavy metal ions from solutions is very important for environmental safety and human health. Poly (amidoamine) (PAMAM) dendrimers are artificial macromolecular materials with unique physical and chemical properties. Abundant amide bonds and amino functional groups provide them with a high affinity for heavy metal ions. Herein, PAMAM-functionalized adsorbents are reviewed in terms of different nanomaterial substrates. Approaches in which PAMAM is grafted onto the surfaces of substrates are described in detail. The adsorption isotherms and kinetics of these adsorbents are also discussed. The effects of PAMAM generation, pH, adsorbent dosage, adsorption time, thermodynamics, and ionic strength on adsorption performance are summarized. Adsorption mechanisms and the further functionalization of PAMAM-grafted adsorbents are reviewed. In addition to the positive results, existing problems are also put forward in order to provide a reference for the optimization of PAMAM-grafted adsorbents of heavy metal ions.

High-tough hydrogels formed via Schiff base reaction between PAMAM dendrimer and Tetra-PEG and their potential as dual-function delivery systems

One way to form tough hydrogels is to create structures with homogeneous networks, such as Tetra-PEG hydrogels. In the current work, Poly(amidoamine) (PAMAM) dendrimers were introduced into Tetra-PEG hydrogels via Schiff base reaction between NH2 groups on PAMAM and CHO groups on 4arm-PEG-aldehyde. The results indicated that the mechanical properties of PAMAM-Tetra-PEG hydrogels were very dependent on the generation of PAMAM. When PAMAM-G1 was introduced, nearly all of the formed hydrogels tended to be mucilage-like semisolids, while PAMAM-G3 or PAMAM-G5 was introduced, no matter what molecular weight or ratio of 4arm-PEG was paired with, the formed hydrogels tended to be solid elastomers, showing high compression strength (0.8722 MPa), and excellent fatigue resistance (~300 cycles of loading-unloading under strain of 90%). The swelling properties of the PAMAM-Tetra-PEG hydrogels were mainly affected by the 4arm-PEG molecular weight, PAMAM generation, and component ratio between PAMAM and 4arm-PEG, reaching to the highest swelling capacity of 1008%. SEM and SAXS confirmed that the formed PAMAM-Tetra-PEG hydrogels were comprised of very uniform networks. Additionally, because of well-defined hydrophobic empty cavities in high-generation PAMAM, the PAMAM-G5-Tetra-PEG hydrogels showed dual-embedding capacity for both hydrophilic and hydrophobic substances, and had potential as dual-function delivery systems.

PAMAM-calix-dendrimers: Synthesis and Thiacalixarene Conformation Effect on DNA Binding.

A convenient method for the synthesis of the first generation PAMAM dendrimers based on the thiacalix[4]arene has been developed for the first time. Three new PAMAM-calix-dendrimers with the macrocyclic core in cone, partial cone, and 1,3-alternate conformations were obtained with high yields. The interaction of the obtained compounds with salmon sperm DNA resulted in the formation of the associates of the size up to 200 nm, as shown by the UV-Vis spectroscopy, DLS, and TEM. It was demonstrated by the CD method that the structure of the DNA did not undergo significant changes upon binding. The PAMAM-calix-dendrimer based on the macrocycle in cone conformation stabilized DNA and prevented its degradation.

ANTIBACTERIAL ACTIVITY OF SOME NANO-ANTIMICROBIAL POLY(AMIDOAMINE) (PAMAM) DENDRIMERIC PRODUCTS

"Dendrimers are synthetic, branched macromolecules. Compared to linear polymers, dendrimers hold multiple advantages as potential carrier molecules: high capacity to incorporate pharmacologically active substances, chemical stability of micelles under physiological conditions, increased bioavailability of active substances covalently or noncovalently bound to dendrimers, due to increased dendrimers capacity to cross biological barriers. The carrier potential of dendrimers has been evaluated in combination with different antibiotics, as an alternative way to address the increasing resistance of Gram-positive and Gram-negative bacteria. This paper presents a study on the intrinsic antibacterial properties of the following poly(amidoamino) (PAMAM) ethylenediamine core dendrimers: PAMAM generation 3.5, PAMAM generation 4.0 and PAMAM-OH generation 4.0. The following bacterial strains were used: Staphylococcus aureus ATCC 29213, Staphylococcus aureus ATCC 6538, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 15442, Enterococcus faecalis ATCC 51299 and a multi-drug resistant (MDR) Acinetobacter baumannii clinical isolate. The dendrimers’ concentrations used in the experiment were established within the range of admissibility obtained following cytotoxicity testing on human cell cultures. The dendrimers’ antibacterial activity varied depending on the concentration and the bacterial species. The antibacterial efficacy was quantified by calculating the percentage and logarithmic reduction of the number of viable microorganisms. The logarithmic reduction varied between 0.06 and 1.10, corresponding to percentage reductions between 13% and 92%. The strongest antibacterial activity of all dendrimers used in this study was registered for the D3.5 dendrimer (50 μg/mL) against Acinetobacter baumannii and Pseudomonas aeruginosa ATCC 15442 reference strain. For A. baumannii, a logarithmic reduction of bacterial activity of 1.10 log10 (percentage reduction in the number of CFU of 92%) was registered, while for P. aeruginosa ATCC 15442 the logarithmic reduction was 0.75 log10 (percentage reduction of 82%)."

Fabrication of PAMAM antimicrobial monolayer via UV induced grafting on the surface of polyethylene terephthalate

Poly (amidoamine) (PAMAM) with 3rd and 5th generation was covalently grafted as the contact active biocidal agent on the surface of polyethylene terephthalate (PET) with the help of UV induced carbene chemistry (PAMAM-g-PET). The graft density and the surface roughness were controlled by turning UV irradiation time and the PAMAM generation. The PAMAM graft monolayer was characterized via the contact angle, XPS, nanoIR, SEM and AFM. The antibacterial ability of PAMAM-g-PET was evaluated ex-vivo with the help of laser scanning confocal microscope (CLSM), and the results indicated that the decorated PET was able to kill both S. aureus and E. coli in the aqueous environment. Increasing the surface graft concentration and using the dendrimer with higher generation enhanced the lethality towards the bacterial. The decorated film was still able to kill the contact bacterial strain when the cationic primary amine groups were shielded by acetyl chloride, however, the bacterial in the suspension was hardly affected in this case. The un-selectivity and instantaneity of carbene chemistry endowed this grafting strategy the potential to be extended to other organic substances.

Magnetic solid phase extraction of heterocyclic aromatic hydrocarbons from environmental water samples with multiwalled carbon nanotube modified magnetic polyamido-amine dendrimers prior to gas chromatography-triple quadrupole mass spectrometer

Present study described a sensitive and efficient method for determination of heterocyclic aromatic hydrocarbons using multiwalled carbon nanotubes modified magnetic polyamido-amine dendrimers (MNPs@PAMAM-Gn@MWCNTs) as adsorbent for magnetic solid-phase extraction (MSPE) coupled with gas chromatography-triple quadrupole mass spectrometer (GC–MS/MS). Some pivotal parameters including PAMAM generation, adsorbent dosage, adsorption time, elution time and volume, pH and humic acid concentration were investigated to achieve the best adsorption efficiencies. Under the optimal conditions, 7-methylquinoline, dibenzothiophene and carbazole had good linearity in the concentration range of 0.005–20 μg L − 1, 9-methylcarbazole, 4-methyldibenzothiophene and 4,6-dimethyl dibenzothiophene had good linearity in the concentration range of 0.001–20 μg L − 1. All the correlation coefficients were higher than 0.996. The detection limits of the targets were in the range of 2.2 × 10−4–1.8 × 10−3 μg L − 1 with precisions less than 8.28% (n = 6). The enrichment factors were in the range of 141–147. The spiked recoveries were in the range of 87.0%-115.1% (n = 3). These results indicated that the method could be a reliable alternative tool for monitoring trace heterocyclic aromatic hydrocarbons in environmental water samples.

“Double-punch” strategy for delivery of viral immunotherapy with prolonged tumor retention and enhanced transfection efficacy

Viral immunotherapy has shown clinical efficacy in treating cancers (e.g., melanoma). Given that viral immunotherapy commonly uses intratumoral injection, prolonging the duration of therapeutic virus at the tumor site can further enhance the antitumor efficacy and reduce potential off-target effects. In this work, we describe a “double-punch” strategy by combining dendrimer platform and injectable hydrogel encapsulation for delivery of an adenovirus encoding Flagrp170 (Adv-Flagrp170), which has been shown to effectively mount a cytotoxic T lymphocyte response through enhanced tumor immunogenicity and optimized antigen cross-presentation. We first complexed PAMAM generation 4 (G4) with Adv (G4/Adv) to strengthen its transfection efficiency and then loaded G4/Adv into a biocompatible and injectable supramolecular hydrogel (SH) made of α-cyclodextrin and 4-arm polyethylene glycol via host-guest interaction. When tested in a murine melanoma model, the G4/Adv complex was shown to have improved retention at the tumor site. The presence of SH facilitated the targeted gene expression in tumor-infiltrating leukocytes, including antigen-presenting dendritic cells. Delivery of Adv-Flagrp170 by both G4 coating and SH encapsulation significantly enhanced its therapeutic efficacy in controlling mouse melanoma (8-fold reduction in tumor volume), which is associated with increased immune activation in the tumor microenvironment as well as decreased adenovirus-reactive antibodies. Taken together, this new formulation may be used to improve the treatment outcome of adenovirus-based cancer immunotherapy.

Guanidyl and imidazolyl integration group-modified PAMAM for gastric adenocarcinoma gene therapy.

Gene therapy has become a potential strategy for cancer treatment. However, the development of efficient gene vectors restricts the application for cancer gene treatment. Functionalization of polymers with functional groups can significantly improve their transfection efficacy. Guanidyl can form bidentate hydrogen with the phosphate groups and phosphate groups are present in DNA and cell membranes, thus increasing DNA condensation and cellular uptake. Imidazolyl has high buffering capacity in endosomal/lysosomal acidic environment, facilitating endosome/lysosome escape. We designed a structure-integrated group of guanidyl and imidazolyl, 2-aminoimidazole (AM), which was conjugated to PAMAM generation 2 (G2) for gene therapy of gastric adenocarcinoma. Molecular docking results illustrated that G2-AM bound with DNA molecule effectively via multiple interactions. A quantitative luciferase assay showed that the transfection efficacy of G2-AM/pGL3 was approximately 100-fold greater than that of G2/pGL3, 90-fold greater than that of imidazolyl-modified G2 (G2-M) /pGL3 and 100-fold greater than that of G5/pGL3 without additional cytotoxicity. After introducing the pTRAIL gene into gastric adenocarcinoma cells, the apoptosis ratio of gastric adenocarcinoma cells treated with G2-AM/pTRAIL was 36.95%, which is much larger than the corresponding ratio of G2/pTRAIL (7.45%), G2-M/pTRAIL (11.33%) and G5/pTRAIL (23.2%). In a gastric adenocarcinoma xenograft model, the in vivo transfection efficacy of G2-AM/pRFP was much greater than that of G2/pRFP and G2-M/pRFP. These results demonstrate that AM could be modified with cationic polymers for potential application in gene delivery and gastric adenocarcinoma gene therapy.

Simultaneous enrichment and determination of cadmium and mercury ions using magnetic PAMAM dendrimers as the adsorbents for magnetic solid phase extraction coupled with high performance liquid chromatography

In present study, a sensitive and efficient method based on magnetic PAMAM dendrimers as the sorbents for magnetic solid-phase extraction (MSPE) coupled with high performance liquid-phase chromatography and ultraviolet variable wavelength detector (HPLC-VWD) was developed for simultaneous determination of trace cadmium and mercury ions. Sodium diethyldithiocarbamate (DDTC-Na) was used as the chelating agent during the elution process. Parameters that would affect the extraction efficiency including PAMAM generation, adsorbent dosage, adsorption time, elution time and volume, pH and coexisting ions were investigated to achieve the best adsorption efficiency. Under the optimal conditions, good linear relationship was obtained in the range of 0.05−200 μg L-1 for Cd2+ and 0.1−200 μg L-1 for Hg2+, and the limits of detection were 0.016 and 0.040 μg L-1, respectively. The spiked recoveries of Cd2+ and Hg2+ were satisfied in the range of 91.5–105% (n = 3). The proposed method was proved to be an alternative and reliable method to determine trace Cd2+ and Hg2+ in water samples.

Photophysics and photochemistry of porphyrin core PAMAM dendrimers. Excited states interaction with quinones

Quenching of excited states of the meso-substituted tetraphenyl porphyrins with PAMAM branches, and one with PAMAM generation 1 peripherally-modified with thiazole groups by p-benzoquinones, were studied in DMF solution. Fluorescence lifetime measurements evidence a static component in the quenching process. The dynamic quenching rate constants were close to the diffusional limit except for the case of duroquinone. Apparent association constants of the porphyrin compounds with the quinones were determined by comparison of static and dynamic measurements of fluorescence quenching. The ground state interaction is very weak with the exception of tetrachlorobenzoquinone. The triplet state decay kinetics and the transient absorption spectra in the presence of the quinones were determined by laser flash photolysis. Triplet quenching rate constants were lower than those of singlet quenching. An electron transfer mechanism was proposed to explain the results. The long-time transient absorption spectra were assigned to the radical cation of the dyes. Relative radical yields were determined and a dependence on the side chains and the quencher was observed.

Amphiphilic Dendrimer as Reverse Micelle: Synthesis, Characterization and Application as Homogeneous Organocatalyst

The core and surface terminal groups are the two main catalytic sites in a dendrimer. In most of the reported examples, the catalytic sites in dendritic catalysis are the surface terminal functional groups. This perspective article concerned with the dendrimer based catalysis, involving these two catalytic sites and the dendrimer cavities. The interior cavities provide the nanoscale reactor sites, by creating reverse micelle like appearance for catalysis. In exploring the significant achievements in this area, a low generation PAMAM dendrimer with amphiphilic nature, having a polymeric core with large number of pendent amino groups was synthesized and concentrated its catalytic activity. The key features with respect to positive and/or negative catalytic activity was highlighted by synthesizing various aryl and heteroaryl 2-substituted benzimidazoles. The synthesized dendritic organocatalyst was proved to be amazingly reactive and gave high yield of products within a few minutes at room temperature with low catalyst loading. Here, a new stable hemiaminal, the species rarely been detected and much less isolated in bulk, was obtained during the synthesis of benzimidazoles. Moreover, this is the first reported method for the synthesis of benzimidazoles, using the homogeneous PAMAM dendrimer as a basic organocatalyst.

Effect of 2nd and 3rd generation PAMAM dendrimers on proliferation, differentiation, and pro-inflammatory cytokines in human keratinocytes and fibroblasts.

BackgroundPoly(amidoamine) (PAMAM) dendrimers are of considerable interest when used as a carrier for topical drugs for the skin, although little is known about their possible side effects. Therefore, our study was about the impact of 2nd and 3rd generation PAMAM dendrimers on human keratinocytes and fibroblasts cells.MethodsThe effect of the tested compounds on collagen biosynthesis was determined using 5[3H]-proline incorporation bioassay. Morphological changes accompanying cell growth inhibition were observed using a confocal microscope. To evaluate the percentage of apoptotic/necrotic cells and the cell growth dynamic of apoptotic features, we performed Annexin V/PI double staining assay, assessed caspase activity, and performed cell cycle analysis by flow cytometry. The flow cytometry method was also used to determine the effect of dendrimers on pro-inflammatory cytokines (IL-6, IL-8 IL-1β).ResultsThe obtained results showed that as the concentration and the generation of dendrimers increased, collagen biosynthesis decreased. We also observed abnormalities in cell differentiation, which may have caused disturbed secretion of pro-inflammatory cytokines. We found that dendrimers cause chronic inflammation which may cause adverse changes in the skin, ultimately– leading to apoptosis in the case of dendrimers in lower concentrations or necrosis at higher concentrations (especially 3rd generation dendrimers). In addition, the inflammatory path induced by the tested compounds was caused by damage in the mitochondria, which we observed as a significant decrease in the mitochondrial membrane potential.ConclusionThe results of our study showed that PAMAM dendrimers can cause disorders of cell proliferation and differentiation and may be the cause of cell cycle deregulation and chronic adverse inflammation.

Preparation of gene drug delivery systems of cationic peptide lipid with 0G-PAMAM as hydrophilic end and its biological properties evaluation.

As an efficient gene delivery, non-viral vectors should have high transfection efficiency, excellent endosomal escape, low cytotoxicity, and the ability to rapidly release the gene into the cytoplasm.Cationic liposome have been widely used as efficient gene carriers, but the cytotoxicity, rapid degradation and low cellular uptake are major drawback impeding its further appolication. Herein, with double lauric acid as hydrophobic chains, tartaric acid as skeleton, 0 generation PAMAM modified with lysine as hydrophilic head, a new type cationic peptide lipid was synthetised. The alkyl chain promote lipid across cell membranes and with membrane fusion, 0 generation PAMAM modified with lysine hydrophilic end amino can contain a large number of protons which can change into ammonium and combine with the DNA negatively charge phosphate groups. It is expected that this carrier has low toxicity, high transfection efficiency and targeting property. By adjusting the cationic liposome/gene weight ratio, the transfection system was optimized to improved gene transfection efficiency, reduce cytotoxicity, and increase property and stability, etc.

Boosted Memory and Improved Brain Bioavailability of Rivastigmine: Targeting Effort to the Brain Using Covalently Tethered Lower Generation PAMAM Dendrimers with Lactoferrin.

Currently, there is no treatment strategy which can reverse the process of neuro-degeneration in progression of Alzheimer's disease (AD). Practically, it is desired to achieve and maintain high therapeutic doses in the brain, but it is hard due to selective permeability of the blood-brain barrier (BBB). In the present study, lactoferrin (Lf) was conjugated to polyamidoamine generation 3.0 (PAMAM G3.0) dendrimers for the effective delivery of rivastigmine (RIV) to the brain. Conjugation of PAMAM G3.0 with lactoferrin was confirmed by FT-IR, 1H NMR, and 2D-NMR spectroscopy as well as AFM techniques. Further, RIV was loaded into PAMAM G3.0 and PAMAM-Lf conjugates. RP-HPLC was used to quantify the drug loading and release as well. Spectroscopic analysis confirmed PAMAM-Lf conjugation, the size of the conjugate was 100.04 ± 3.1 nm, and after RIV loading, the size was increased up to 216.13 ± 2.3 nm. Atomic force microscopic results revealed that the root-mean-square roughness ( Rq) and surface roughness ( Ra) were 6.31 and 5.27 nm, respectively, along with other parameters, Skewness and Kurtosis, which were 0.522 and 2.50, respectively. In vitro drug release from the PAMAM-Lf-RIV conjugate was sustained up to more than 100 h, and that of naive RIV was quite rapid (approxmately 99% release was observed in 8 h). Ex vivo hemotoxicity of the PAMAM-Lf-RIV conjugate was almost 9.8-fold lesser than the PAMAM G3.0 ( p < 0.0001), 7.77 times that of PAMAM-enc-RIV and 5 times that of naïve RIV ( p < 0.0001), respectively. The in vivo targeting potency of the conjugate was investigated in a rat model. Bioavailability of the RIV was enhanced 7.87 times compared to RIV along with improved pharmacokinetic parameters. Brain uptake of the drug was improved when treated with PAMAM-Lf-RIV over the RIV and PAMAM-enc-RIV, almost 8 and 4.2 times, respectively, after 4 h of the administration. Additionally, the behavioral studies revealed that PAMAM-Lf-RIV significantly enhanced the overall locomotor activity with higher ambulations over the pure drug and PAMAM-enc-RIV formulation. The outcome of the novel object recognition test was an indirect evidence of memory improvement. Conclusively, the development and characterization of PAMAM-Lf-RIV resulted in improved brain uptake and brain bioavailability with boosted memory, which can be beneficial in the treatment of Alzheimer's.