Purpose: To develop a safe, lipid-based non-viral gene delivery system that achieves high transfection efficiency in the presence of serum proteins. Methods: Polyplexes with the pAcGFP1-C1 plasmid were formed in phosphate buffered saline, pH 7.4 (PBS) using the novel poly[N-(2-hydroxypropyl)methacrylamide]-poly(N,N-dimethylaminoethylmethacrylate) diblock copolymer (pHPMA-b-pDMAEMA) at N/P=4. Cationic-Liposomes were prepared from a dried lipid film comprised of equimolar 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) and 1,2-dioleoyl-sn-glycero-3- phosphoethanolamine (DOPE). Lipopolyplexes were fabricated at lipid/DNA weight ratios up to 40. Particle size distribution and zeta potential of lipopolyplexes were determined by dynamic light scattering. HeLa cells viability in the presence and absence of lipopolyplexes was quantified using the CellTiter-Glo® luminescent assay. HeLa cell transfection efficiency in the presence and absence of FBS was visually assessed by confocal microscopy and quantitatively compared to the TurboFect™ control. Results: pHPMA-b-pDMAEMA exhibited a high condensation capacity of 1 μg of pDNA per 0.513 μg of polymer (N/P=1). Lipid-coating of polyplexes at lipid/DNA weight ratios up to 40 resulted in particle sizes +25 mV. Exposure to FBS significantly increased mean particle size to >300 nm, reduced zeta potential to -10 mV, and augmented polydispersity. Lipid coating of polyplexes only decreased HeLa cell viability at lipid/DNA ratios >20. HeLa transfection with lipopolyplexes was most effective at lipid/DNA = 20 and was significantly greater in the presence of FBS than measured for lipid-free polyplexes. Conclusion: Lipid coating of pHPMA-b-pDMAEMA/DNA polyplexes with an equimolar DOTAP/DOPE mixture at a lipid/DNA ratio = 20 effectively enhances in vitro transfection efficiency of HeLa cells in the presence of serum proteins.

Introduction: For years, injectable polymeric nanoparticles (NPs) have been developed for delivering therapeutic agents to the tumors. Frequently, NPs surface have been modified with different moieties and/or ligands to impart stealth effect and/or elicit specific cellular interactions, both known to dramatically affect the in vivo fate and efficacy of these NPs. Areas covered: We discuss different types of ligands and molecules used for surface functionalization of polymeric NPs for tumor drug delivery. First, we summarize methods used through the literature for surface modification of polymeric NPs, then discuss challenges that face researchers either in decorating NPs with desired surface functionalities, characterizing functionalized surfaces or achieving intended cellular interactions and in vivo effects. Expert opinion: Modification of NP surfaces dramatically alters their behavior and favorably enhances their therapeutic efficacy. Choice of surface ligand/functionality should be based on intended therapeutic outcomes, taking into consideration the potential of clinical translation and scale up of the developed systems.

Introduction: For years, injectable polymeric nanoparticles (NPs) have been developed for delivering therapeutic agents to the tumors. Frequently, NPs surface have been modified with different moieties and/or ligands to impart stealth effect and/or elicit specific cellular interactions, both known to dramatically affect the in vivo fate and efficacy of these NPs. Areas covered: We discuss different types of ligands and molecules used for surface functionalization of polymeric NPs for tumor drug delivery. First, we summarize methods used through the literature for surface modification of polymeric NPs, then discuss challenges that face researchers either in decorating NPs with desired surface functionalities, characterizing functionalized surfaces or achieving intended cellular interactions and in vivo effects. Expert opinion: Modification of NP surfaces dramatically alters their behavior and favorably enhances their therapeutic efficacy. Choice of surface ligand/functionality should be based on intended therapeutic outcomes, taking into consideration the potential of clinical translation and scale up of the developed systems.

There has been an increasing interest to develop new types of stimuli-responsive drug delivery vehicles with high drug loading and controlled release properties for chemotherapeutics. An acid-labile poly(ethylene oxide)-block-polyphosphoester-graft -PTX drug conjugate (PEO-b-PPE-g-PTX G2) degradable, polymeric paclitaxel (PTX) conjugate containing ultra-high levels of PTX loading is improved significantly, in this second-generation development, which involves connection of each PTX molecule to the polymer backbone via a pH-sensitive -thiopropionate linkage. The PEO-b-PPE-g-PTX G2 forms well-defi ned nanoparticles in an aqueous solution, by direct dissolution into water, with a number-averaged hydrodynamic diameter of 11431 nm, and exhibits a PTX loading capacity as high as 53 wt%, with a maximum PTX concentration of 0.68 mg mL−1 in water (vs 1.7 g mL−1 for free PTX). The PEO-b-PPE-g-PTX G2 shows accelerated drug release under acidic conditions (50 wt% PTX released in 8 d) compared with neutral conditions (20 wt% PTX released in 8 d). Compared to previously reported polyphosphoester-based PTX drug conjugates, PEO-b-PPE-g-PTX G1 without the -thiopropionate linker, the PEO-b-PPE-g-PTX G2 shows pH-triggered drug release property and 5- to 8-fold enhanced in vitro cytotoxicity against two cancer cell lines.

Aim: Alendronate (AL) is a nitrogen-containing bisphosphonate drug that exhibits limited oral bioavailability due to predominantly hydrophilic molecular properties. To enhance oral absorption of this important osteoporosis drug, a novel ion-pairing strategy using the cationic polymer polyethylenimine (PEI) was explored as an initial step of an alternate oral drug delivery strategy that attempts to prepare polymer-encapsulated ion pair nanoparticles. Methodology: Electrostatically stabilized AL/PEI association complexes were fabricated by combining AL and PEI solutions prepared in 0.05 M acetate buffer, pH 5.0, at different AL/PEI charge ratios under stirring. The free fraction of AL after complexation with PEI was quantified spectrophotometrically at λ=300 nm using ferric chloride. Particle size distribution and zeta potential of ion pairs formed at different molar AL/PEI ratios were measured by dynamic laser light scattering. Results: The complexation efficiency of PEI was low until an AL/PEI charge ratio of1:1.7. Increasing PEI concentrations effectively decreased the free fraction of AL implying formation of stable ion pairs between the negatively charged AL and the positively charged polymer. The lowest fraction of free AL was 18.7% measured at an AL/PEI charge ratio of 1:33. The mean hydrodynamic diameter of nanoassemblies decreased with increasing AL/PEI charge ratio reaching a limiting value of 71±1.4 nm at AL/PEI=1:33. Corresponding zeta potential measured for these association complexes was +37±2.8 mV. Conclusion: AL/PEI charge ratio greater than 1:1.7 facilitates effective formation of electrostatically stabilized ion pairs that carry a significant positive surface charge indicative of substantial colloidal stability in aqueous solution. The small size of AL/PEI complexes fabricated at 1:33 favors these ion pairs for subsequent encapsulation into biocompatible polymers suitable for oral drug delivery.

Aim: Alendronate (AL) is a nitrogen-containing bisphosphonate drug that exhibits limited oral bioavailability due to predominantly hydrophilic molecular properties. To enhance oral absorption of this important osteoporosis drug, a novel ion-pairing strategy using the cationic polymer polyethylenimine (PEI) was explored as an initial step of an alternate oral drug delivery strategy that attempts to prepare polymer-encapsulated ion pair nanoparticles. Methodology: Electrostatically stabilized AL/PEI association complexes were fabricated by combining AL and PEI solutions prepared in 0.05 M acetate buffer, pH 5.0, at different AL/PEI charge ratios under stirring. The free fraction of AL after complexation with PEI was quantified spectrophotometrically at λ=300 nm using ferric chloride. Particle size distribution and zeta potential of ion pairs formed at different molar AL/PEI ratios were measured by dynamic laser light scattering. Results: The complexation efficiency of PEI was low until an AL/PEI charge ratio of1:1.7. Increasing PEI concentrations effectively decreased the free fraction of AL implying formation of stable ion pairs between the negatively charged AL and the positively charged polymer. The lowest fraction of free AL was 18.7% measured at an AL/PEI charge ratio of 1:33. The mean hydrodynamic diameter of nanoassemblies decreased with increasing AL/PEI charge ratio reaching a limiting value of 71±1.4 nm at AL/PEI=1:33. Corresponding zeta potential measured for these association complexes was +37±2.8 mV. Conclusion: AL/PEI charge ratio greater than 1:1.7 facilitates effective formation of electrostatically stabilized ion pairs that carry a significant positive surface charge indicative of substantial colloidal stability in aqueous solution. The small size of AL/PEI complexes fabricated at 1:33 favors these ion pairs for subsequent encapsulation into biocompatible polymers suitable for oral drug delivery.

Aim: Alendronate (AL) is a nitrogen-containing bisphosphonate drug that exhibits limited oral bioavailability due to predominantly hydrophilic molecular properties. To enhance oral absorption of this important osteoporosis drug, a novel ion-pairing strategy using the cationic polymer polyethylenimine (PEI) was explored as an initial step of an alternate oral drug delivery strategy that attempts to prepare polymer-encapsulated ion pair nanoparticles. Methodology: Electrostatically stabilized AL/PEI association complexes were fabricated by combining AL and PEI solutions prepared in 0.05 M acetate buffer, pH 5.0, at different AL/PEI charge ratios under stirring. The free fraction of AL after complexation with PEI was quantified spectrophotometrically at λ=300 nm using ferric chloride. Particle size distribution and zeta potential of ion pairs formed at different molar AL/PEI ratios were measured by dynamic laser light scattering. Results: The complexation efficiency of PEI was low until an AL/PEI charge ratio of1:1.7. Increasing PEI concentrations effectively decreased the free fraction of AL implying formation of stable ion pairs between the negatively charged AL and the positively charged polymer. The lowest fraction of free AL was 18.7% measured at an AL/PEI charge ratio of 1:33. The mean hydrodynamic diameter of nanoassemblies decreased with increasing AL/PEI charge ratio reaching a limiting value of 71±1.4 nm at AL/PEI=1:33. Corresponding zeta potential measured for these association complexes was +37±2.8 mV. Conclusion: AL/PEI charge ratio greater than 1:1.7 facilitates effective formation of electrostatically stabilized ion pairs that carry a significant positive surface charge indicative of substantial colloidal stability in aqueous solution. The small size of AL/PEI complexes fabricated at 1:33 favors these ion pairs for subsequent encapsulation into biocompatible polymers suitable for oral drug delivery.

Oral bioavailability of the anti-osteoporotic drug alendronate (AL) is limited to ≤ 1% due to unfavorable physicochemical properties. To augment absorption across the gastrointestinal mucosa, an ion pair complex between AL and polyethyleneimine (PEI) was formed and incorporated into nanostructured lipid carriers (NLCs) using a modified solvent injection method. When compared to free AL, ion pairing with PEI increased drug encapsulation efficiency in NLCs from 10% to 87%. Drug release from NLCs measured in vitro using fasted state simulated intestinal fluid, pH 6.5 (FaSSIF-V2) was significantly delayed after PEI complexation. Stability of AL/PEI was pH-dependent resulting in 10-fold faster dissociation of AL in FaSSIF-V2 than measured at pH 7.4. Intestinal permeation properties estimated in vitro across Caco-2 cell monolayers revealed a 3-fold greater flux of AL encapsulated as hydrophobic ion complex in NLCs when compared to AL solution (Papp = 8.43 ± 0.14 × 10−6 cm/s and vs. 2.76 ± 0.42 × 10−6 cm/s). Cellular safety of AL/PEI-containing NLCs was demonstrated up to an equivalent AL concentration of 2.5 mM. These results suggest that encapsulation of AL/PEI in NLCs appears a viable drug delivery strategy for augmenting oral bioavailability of this clinically relevant bisphosphonate drug and, simultaneously, increase gastrointestinal safety.

Oral bioavailability of the anti-osteoporotic drug alendronate (AL) is limited to ≤ 1% due to unfavorable physicochemical properties. To augment absorption across the gastrointestinal mucosa, an ion pair complex between AL and polyethyleneimine (PEI) was formed and incorporated into nanostructured lipid carriers (NLCs) using a modified solvent injection method. When compared to free AL, ion pairing with PEI increased drug encapsulation efficiency in NLCs from 10% to 87%. Drug release from NLCs measured in vitro using fasted state simulated intestinal fluid, pH 6.5 (FaSSIF-V2) was significantly delayed after PEI complexation. Stability of AL/PEI was pH-dependent resulting in 10-fold faster dissociation of AL in FaSSIF-V2 than measured at pH 7.4. Intestinal permeation properties estimated in vitro across Caco-2 cell monolayers revealed a 3-fold greater flux of AL encapsulated as hydrophobic ion complex in NLCs when compared to AL solution (Papp = 8.43 ± 0.14 × 10−6 cm/s and vs. 2.76 ± 0.42 × 10−6 cm/s). Cellular safety of AL/PEI-containing NLCs was demonstrated up to an equivalent AL concentration of 2.5 mM. These results suggest that encapsulation of AL/PEI in NLCs appears a viable drug delivery strategy for augmenting oral bioavailability of this clinically relevant bisphosphonate drug and, simultaneously, increase gastrointestinal safety.

Oral bioavailability of the anti-osteoporotic drug alendronate (AL) is limited to ≤ 1% due to unfavorable physicochemical properties. To augment absorption across the gastrointestinal mucosa, an ion pair complex between AL and polyethyleneimine (PEI) was formed and incorporated into nanostructured lipid carriers (NLCs) using a modified solvent injection method. When compared to free AL, ion pairing with PEI increased drug encapsulation efficiency in NLCs from 10% to 87%. Drug release from NLCs measured in vitro using fasted state simulated intestinal fluid, pH 6.5 (FaSSIF-V2) was significantly delayed after PEI complexation. Stability of AL/PEI was pH-dependent resulting in 10-fold faster dissociation of AL in FaSSIF-V2 than measured at pH 7.4. Intestinal permeation properties estimated in vitro across Caco-2 cell monolayers revealed a 3-fold greater flux of AL encapsulated as hydrophobic ion complex in NLCs when compared to AL solution (Papp = 8.43 ± 0.14 × 10−6 cm/s and vs. 2.76 ± 0.42 × 10−6 cm/s). Cellular safety of AL/PEI-containing NLCs was demonstrated up to an equivalent AL concentration of 2.5 mM. These results suggest that encapsulation of AL/PEI in NLCs appears a viable drug delivery strategy for augmenting oral bioavailability of this clinically relevant bisphosphonate drug and, simultaneously, increase gastrointestinal safety.