Injectable Poloxamer Hydrogel Formulations for Intratympanic Delivery of Dexamethasone.

BACKGROUND: In this study, we prepared and evaluated an injectable poloxamer (P407) hydrogel formulation for intratympanic (IT) delivery of dexamethasone (DEX). METHODS: DEX-loaded P407 hydrogels were characterized in terms of thermogelation, drug loading capacities, particle size, and drug release. The in vivo toxicity and drug absorption of the DEX-loaded P407 formulation after IT injection were evaluated using an animal model by performing histopathological analysis and drug concentration measurements. RESULTS: The P407 hydrogel effectively solubilized hydrophobic DEX and demonstrated a sustained release compared to the hydrophilic DEX formulation. The in vivo study showed that the hydrogel formulation delivered considerable drug concentrations to the inner ear and displayed a favorable safety profile without apparent cytotoxicity or inflammation. CONCLUSION: P407 hydrogel can be useful as an injectable inner ear delivery formulation for hydrophobic drugs due to their biocompatibility, drug-solubilizing capacity, thermogelation, and controlled release.

Applications of Biomaterials in 3D Cell Culture and Contributions of 3D Cell Culture to Drug Development and Basic Biomedical Research.

The process of evaluating the efficacy and toxicity of drugs is important in the production of new drugs to treat diseases. Testing in humans is the most accurate method, but there are technical and ethical limitations. To overcome these limitations, various models have been developed in which responses to various external stimuli can be observed to help guide future trials. In particular, three-dimensional (3D) cell culture has a great advantage in simulating the physical and biological functions of tissues in the human body. This article reviews the biomaterials currently used to improve cellular functions in 3D culture and the contributions of 3D culture to cancer research, stem cell culture and drug and toxicity screening.

Tempo-spatial Activation of Sequential Quadruple Stimuli for High Gene Expression of Polymeric Gene Nanocomplexes.

The clinical application of intracellular gene delivery via nanosized carriers is hindered by intracellular multistep barriers that limit high levels of gene expression. To solve these issues, four different intracellular or external stimuli that can efficiently activate a gene carrier, a gene, or a photosensitizer (pheophorbide A [PhA]) were assessed in this study. The designed nanosized polymeric gene complexes were composed of PhA-loaded thiol-degradable polycation (PhA@RPC) and cytomegalovirus (CMV) promoter-equipped pDNA. After cellular internalization of the resulting PhA@RPC/pDNA complexes, the complexes escaped endosomal sequestration, owing to the endosomal pH-induced endosomolytic activity of RPC in PhA@RPC. Subsequently, intracellular thiol-mediated polycation degradation triggered the release of PhA and pDNA from the complexes. Late exposure to light (for example, 12 h post-treatment) activated the released PhA and resulted in the production of reactive oxygen species (ROS). Intracellular ROS successively activated NF-κB, which then reactivated the CMV promoter in the pDNA. These sequential, stimuli-responsive chemical and biological reactions resulted in high gene expression. In particular, the time-point of light exposure was very significant to tune efficient gene expression as well as negligible cytotoxicity: early light treatment induced photochemical internalization but high cytotoxicity, whereas late light treatment influenced the reactivation of silent pDNA via PhA-generated ROS and activation of NF-κB. In conclusion, the quadruple triggers, such as pH, thiol, light, and ROS, successively influenced a gene carrier (RPC), a photosensitizer, and a genetic therapeutic, and the tempo-spatial activation of the designed quadruple stimuli-activatable nanosized gene complexes could be potential in gene delivery applications.

Bioreducible Poly(ethylene glycol)-Triphenylphosphonium Conjugate as a Bioactivable Mitochondria-Targeting Nanocarrier.

Bioactivable nanocarrier systems have favorable characteristics such as high cellular uptake, target specificity, and an efficient intracellular release mechanism. In this study, we developed a bioreducible methoxy polyethylene glycol (mPEG)-triphenylphosphonium (TPP) conjugate (i.e., mPEG-(ss-TPP)2 conjugate) as a vehicle for mitochondrial drug delivery. A bioreducible linkage with two disulfide bond-containing end groups was used at one end of the hydrophilic mPEG for conjugation with lipophilic TPP molecules. The amphiphilic mPEG-(ss-TPP)2 self-assembled in aqueous media, which thereby formed core-shell structured nanoparticles (NPs) with good colloidal stability, and efficiently encapsulated the lipophilic anticancer drug doxorubicin (DOX). The DOX-loaded mPEG-(ss-TPP)2 NPs were characterized in terms of their physicochemical and morphological properties, drug-loading and release behaviors, in vitro anticancer effects, and mitochondria-targeting capacity. Our results suggest that bioreducible DOX-loaded mPEG-(ss-TPP)2 NPs can induce fast drug release with enhanced mitochondrial uptake and have a better therapeutic effect than nonbioreducible NPs.

Thermosensitive progesterone hydrogel: a safe and effective new formulation for vaginal application.

PURPOSE: The safe and functional delivery of progesterone through the vaginal route remains an unmet clinical need. The purpose of this work is to prepare a new progesterone (P4) gel for vaginal application using a thermosensitive mucoadhesive polymer, glycol chitin (GC). METHOD: Thermogelling, mucoadhesive, mechanical, and viscoelastic properties of GC and the new formulation were evaluated using rheometry. In vitro release profile and the bioactivity of P4 were determined using vaginal fluid simulant (VFS) pH 4.2, and PR-reporter gene assay, respectively. In vitro safety of the formulations was tested using (VK2/E6E7) vaginal epithelial cell line and Lactobacillus Crispatus. Finally, in vivo safety and the efficacy of this formulation were evaluated using an endometrial hypoplasia mouse model. RESULTS: Results shows the aqueous solution of 5%; (w/v) GC loaded with 0.1%; (w/v) P4 prepared in pH 4.2, (GC-P4), forms a thermosensitive mucoadhesive hydrogel and can maintain stable physical properties at 37 °C. GC-P4 gel release 50% of P4 in 4 h after exposure to VFS, and no significant decrease in % viability of VK2/E6E7 or Lactobacillus was found after exposure to 5% GC or GC-P4. GC-P4 does not exhibit obvious toxicities to vaginal tissue in vivo even after repeated application. Efficacy studies indicated that GC-P4 was capable of preventing the progression of simple endometrial hyperplasia (SEH) to complex atypical endometrial hyperplasia (CAEH) in vivo. CONCLUSIONS: Results indicates that GC-P4 retains many characteristics for an effective vaginal delivery system for P4. Therefore we believe that GC-P4 formulation is a promising alternative to current vaginal P4 formulation.

Biarmed poly(ethylene glycol)-(pheophorbide a)2 conjugate as a bioactivatable delivery carrier for photodynamic therapy.

In the study presented here, we developed a bioreducible biarmed methoxy poly(ethylene glycol)-(pheophorbide a)2 (mPEG-(ss-PhA)2) conjugate for cancer-cell-specific photodynamic therapy (PDT). PhA molecules were chemically conjugated with biarmed linkages at one end of the mPEG molecule via disulfide bonds. Under aqueous conditions, the amphiphilic mPEG-(ss-PhA)2 conjugate self-assembled to form core-shell-structured nanoparticles (NPs) with good colloidal stability. The mPEG-(ss-PhA)2 NPs exhibited intramolecular and intermolecular self-quenching effects that enabled the NPs to remain photoinactive in a physiological buffer. However, the dissociation of the NP structure was effectively induced by the cleavage of the disulfide bonds in response to intracellular reductive conditions, triggering the rapid release of PhA molecules in a photoactive form. In cell-culture systems, in addition to significant phototoxicity and intracellular uptake, we observed that the dequenching processes of PhA in the mPEG-(ss-PhA)2 NPs highly depended on the expression of intracellular thiols and that supplementation with glutathione monoethylester facilitated more rapid PhA release and enhanced the PhA phototoxicity. These findings suggest that the bioreducible activation mechanism of mPEG-(ss-PhA)2 NPs in cancer cells can maximize the cytosolic dose of active photosensitizers to achieve high cytotoxicity, thereby enhancing the treatment efficacy of photodynamic cancer treatment.

Preparation and irradiation of Pluronic F127-based thermoreversible and mucoadhesive hydrogel for local delivery of naproxen.

To improve physical properties and modulate the mucoadhesive hydrogel formulation via cross-linking by radiation, hydrogels were prepared using thermoreversible polymer Pluronic F127 (PF127) and mucoadhesive polymer carbopol 934P (C934P). As a model drug, naproxen was loaded in the hydrogel formulation. Sol-gel transition temperatures of hydrogels were measured by the tube-inversion method. The mucoadhesive potential of each formulation was determined by measuring the force required to detach the formulation from oral mucosal tissue. To strengthen the mechanical properties, the formulations were irradiated using an electronic beam. Drug release from the hydrogels and the cytotoxicity of each formulation were investigated. Sol-gel transition temperatures of the formulations were decreased by the addition of carbopol and were close to body temperature. The mucoadhesive force of the PF127 formulation was increased by addition of carbopol. In vitro release was sustained and the release rate was reduced by the addition of carbopol. After irradiation, the mucoadhesive force was increased about five-fold especially in the case of PF127 23% (9.7 kPa) and in vitro release was not sustained further. In conclusion, the use of a PF127 formulation incorporating a mucoadhesive polymer could effectively and safely improve oral residence time and absorption of naproxen. Irradiated formulations showed permanent cross-linking and improved properties.

Beyond hydrophilic polymers in amphiphilic polymer-based self-assembled NanoCarriers: Small hydrophilic carboxylate-capped disulfide drug delivery system and its multifunctionality and multispatial targetability.

Due to increasing safety and intracellular delivery concerns about hydrophilic polymers in amphiphilic polymer-based nanoparticles (NPs), this study investigates small hydrophilic molecule-stabilized NPs for effective intracellular delivery with multiorganelle targetability and dual responsiveness to acidic pH/glutathione (GSH). In the construction of small hydrophilic molecule-stabilized NP (MSPCL-NP), the A-B-A-type amphiphilic polymer (MSPCL-P) is composed of two short hydrophilic carboxylate-capped disulfide derivatives (A) that replace hydrophilic polymers and assist in providing colloidal stability and preventing antibody (e.g., at least anti-PEG antibody)-mediated specific interactions and complement activation in the plasma and a hydrophobic multiple disulfide-containing poly(ε-caprolactone) block (B) that carries hydrophobic drugs. The carboxylates on the surface of MSPCL-NP target the acidic extratumoral/endolysosomal milieu by sensing and buffering acidic pH values, and the hydrophobic carboxylic acids improve adsorptive endocytosis and effective endosomal escape. Multiple disulfide linkages selectively target cytosolic GSH, resulting in rapid drug release from the destroyed MSPCL-NP via the cleavage of disulfide bonds in MSPCL-P. Doxorubicin (DOX)-loaded NP (DOX@MSPCL-NP) exerts strong effects on killing cells in vitro and inhibits tumor growth in HCT116 xenograft tumor-bearing mice. In conclusion, the multifunctionality and multispatial targetability of MSPCL-NP might effectively overcome various sequential drug delivery hurdles, ranging from blood circulation to drug release. Furthermore, the introduction of small hydrophilic molecules represents a potential strategy to make self-assembled NPs without the use of hydrophilic polymers.

Thermosensitive gallic acid-conjugated hexanoyl glycol chitosan as a novel wound healing biomaterial.

In the present study, a novel synthetic tissue adhesive material capable of sealing wounds without the use of any crosslinking agent was developed by conjugating thermosensitive hexanoyl glycol chitosan (HGC) with gallic acid (GA). The degree of N-gallylation was manipulated to prepare GA-HGCs with different GA contents. GA-HGCs demonstrated thermosensitive sol-gel transition behavior and formed irreversible hydrogels upon natural oxidation of the pyrogallol moieties in GA, possibly leading to GA-HGC crosslinks through intra/intermolecular hydrogen bonding and chemical bonds. The GA-HGC hydrogels exhibited self-healing properties, high compressive strength, strong tissue adhesive strength and biodegradability that were adjustable according to the GA content. GA-HGCs also presented excellent biocompatibility and wound healing effects. The results of in vivo wound healing efficacy studies on GA-HGC hydrogels indicated that they significantly promote wound closure and tissue regeneration by upregulating growth factors and recruiting fibroblasts compared to the untreated control group.

Octanoyl glycol chitosan enhances the proliferation and differentiation of tonsil-derived mesenchymal stem cells.

Biofunctional polymers have been widely used to enhance the proliferation and functionality of stem cells. Here, we report the development of a new biofunctional polymer, octanoyl glycol chitosan (OGC), and demonstrate its effects on the cell cycle and stem cell function using tonsil-derived mesenchymal stem cells (TMSCs). OGC treatment (100 µg/mL) significantly increased the proliferation of TMSCs, which could be attributed to cyclin D1 up-regulation in the G1 phase of the cell cycle. Additionally, OGC enhanced the ability of TMSCs to differentiate into adipocytes, chondrocytes, and osteoblasts. Taken together, this new biofunctional polymer, OGC, can promote stemness and osteogenesis, as well as induce stem cell proliferation by enhancing the intracellular metabolic rate and regulating the cell cycle. Thus, in the future, OGC could be a potential therapeutic additive for improving stem cell function.

Preparation and characterization of CdSe/ZnS quantum dots encapsulated in poly(ethylene glycol)-b-poly(D,L-lactide) micelle nanoparticles.

The final goal of this study is to develop multi-functional organic/inorganic hybrid nanoparticles, which can be utilized as biomedical imaging probes and drug delivery carriers. As an initial step toward this goal, we encapsulated CdSe/ZnS quantum dots (QDs) into poly(ethylene glycol)-b-poly(D,L-lactide) (PEG-PLA) micelles using a solid dispersion method. The size and fluorescent intensity of QDs encapsulated in PEG-PLA micelles depended on the amount of incorporated QDs. For example, when the amount of QDs increased from 0.1 to 1.0 microg, the mean diameter increased from 24.2 +/- 6.0 to 211.2 +/- 6.5 nm and the fluorescent intensity changed from 10.2 +/- 1.0 to 469.9 +/- 15.6 (RFU). Stability studies showed that the size and zeta-potential (ZP) of QDs encapsulated in PEG-PLA micelles (QEMs) did not change significantly in response to a change in pH conditions or under a 10% serum condition. We also tested the cytotoxicity and cellular uptake of the QEMs. The viability of HeLa cells treated with micelles for 24 h was 80-100% in various concentration ranges of micelles. Confocal laser scanning microscopic images showed that the QEMs penetrated into the cells, particularly into the cytosolic compartments. Our results suggest that the QEMs may be a promising multi-functional nanocarrier for biomedical imaging and drug delivery.

Thermo-irreversible glycol chitosan/hyaluronic acid blend hydrogel for injectable tissue engineering.

Thermogels that undergo temperature-dependent sol-gel transition have recently attracted attention as a promising biomaterial for injectable tissue engineering. However, conventional thermogels usually suffer from poor physical properties and low cell binding affinity, limiting their practical applications. Here, a simple approach for developing a new thermogel with enhanced physical properties and cell binding affinity is proposed. This thermogel (AcHA/HGC) was obtained by simple blending of a new class of polysaccharide-based thermogel, N-hexanoyl glycol chitosan (HGC), with a polysaccharide possessing good cell binding affinity, acetylated hyaluronic acid (AcHA). Gelation of AcHA/HGC was initially triggered by the thermosensitive response of HGC and gradually intensified by additional physical crosslinking mechanisms between HGC and AcHA, resulting in thermo-irreversible gelation. Compared to the thermos-reversible HGC hydrogel, the thermo-irreversible AcHA/HGC hydrogel exhibited enhanced physical stability, mechanical properties, cell binding affinity, and tissue compatibility. These results suggest that our thermo-irreversible hydrogel is a promising biomaterial for injectable tissue engineering.

Photo- and pH-Responsive Polycarbonate Block Copolymer Prodrug Nanomicelles for Controlled Release of Doxorubicin.

Photo/pH dual-responsive amphiphilic diblock copolymers with alkyne functionalized pendant o-nitrobenzyl ester group are synthesized using poly(ethylene glycol) as a macroinitiator. The pendant alkynes are functionalized as aldehyde groups by the azide-alkyne Huisgen cycloaddition. The anticancer drug doxorubicin (DOX) molecules are then covalently conjugated through acid-sensitive Schiff-base linkage. The resultant prodrug copolymers self-assemble into nanomicelles in aqueous solution. The prodrug nanomicelles have a well-defined morphology with an average size of 20-40 nm. The dual-stimuli are applied individually or simultaneously to study the release behavior of DOX. Under UV light irradiation, nanomicelles are disassembled due to the ONB ester photocleavage. The light-controlled DOX release behavior is demonstrated using fluorescence spectroscopy. Due to the pH-sensitive imine linkage the DOX molecules are released rapidly from the nanomicelles at the acidic pH of 5.0, whereas only minimal amount of DOX molecules is released at the pH of 7.4. The DOX release rate is tunable by applying the dual-stimuli simultaneously. In vitro studies against colon cancer cells demonstrate that the nanomicelles show the efficient cellular uptake and the intracellular DOX release, indicating that the newly designed copolymers with dual-stimuli-response have significant potential applications as a smart nanomedicine against cancer.

Synthesis of poly(ethylene glycol)-polydiacetylene conjugates and their micellar and chromic characteristics.

In this report, novel polymer-lipid conjugates were synthesized and their unique micellar and chromic properties were studied. The conjugates were synthesized by the liquid-phase peptide synthesis method using methoxy(polyethylene glycol)-amine (mPEG-NH2, MW2000) as a supporting material. One and two 10,12-pentacosadiynoic acid (PCDA) groups were conjugated to mPEG-NH2 to prepare mPEG-PCDA and mPEG-PCDA2, respectively. The polymer conjugates could form nanometer-sized micelles in aqueous media and be further polymerized under the exposure of UV 254 nm due to the UV sensitive nature of PCDA. It was observed that mPEG-PCDA2 micelle showed very distinctive photochromism and thermochromism in response to UV or heat, whereas mPEG-PCDA did not display any chromic properties. Moreover, a distinctive chromic property change was observed by adding alpha-cyclodextrin as a model biological molecule to the micelle solution. Due to their unique properties such as high water-solubility, cross-linkable micelle formation with a nano-scaled size, and stimuli-responsive chromic nature, the polymer-lipid conjugates would be useful for various biomedical applications, in particular as a nano-carrier for drug delivery and biosensor.

Preparation of orthogonally functionalized surface using micromolding in capillaries technique for the control of cellular adhesion.

This study presents a simple method for the fabrication of an orthogonal surface that can be applied for cell patterning without the need to immobilize specific adhesive peptides, proteins, or extracellular matrix (ECM) for cell attachment. Micromolding in capillaries (MIMIC) produced two distinctive regions. One region contained poly(ethylene glycol)-poly(D,L-lactide) diblock copolymer (PEG-PLA) designed to provide a biological barrier to the nonspecific binding of proteins and fibroblast cells. The other region was coated with polyelectrolyte (PEL) to promote the adhesion of biomolecules including proteins and cells. Resistance to the adsorption of proteins increased with the length of PEG and PLA chains because the longer PEG chain increased the PEG layer thickness and the longer PLA chain induced stronger interaction with the PEL surface. The PEG5k-PLA2.5k (20mg/ml) was the most efficient candidate for the prevention of protein adhesion among the PEG-PLA copolymers examined. The orthogonal functionality of prepared surfaces having PEL regions and background PEG-PLA regions resulted in rapid patterning of biomolecules. Fluorescein isothiocyanate-tagged bovine serum albumin (FITC-BSA) and fibroblast cells successfully adhered to the exposed PEL surfaces. Although methods for cell patterning generally require an adhesive protein layer on the desired area, these fabricated surfaces without adhesive proteins provide a gentle microenvironment for cells. In addition, our proposed approach could easily control patterns, sizes, and shapes at micron scale.

Synthesis and characterization of bioreducible cationic biarm polymer for efficient gene delivery.

We synthesized a new cationic AB2 miktoarm block copolymer consisting of one poly (ethylene glycol) (PEG) block and two cationic poly (l-lysine) (PLL) blocks, wherein the PLL blocks were conjugated to the PEG blocks with or without a bioreducible linker (disulfide bonds). Bioreducible and non-bioreducible miktoarm block copolymers (mPEG-(ss-PLL)2 and mPEG-PLL2) were prepared for efficient gene delivery as a non-viral gene delivery approach. Both cationic copolymers (bioreducible and nonbioreducible) efficiently formed the nanopolyplexes with plasmid DNA (pDNA) through electrostatic interaction at different weight ratio of polymer and pDNA. Gene condensation ability of the polymers and release of the DNA under reduction condition were measured by gel electrophoresis. Dynamic light scattering (DLS) and field-emission transmission electron microscopy (FE-TEM) were used to measure the average hydrodynamic diameter and morphology of the nanoparticles, respectively. The bioreducible nanopolyplexes showed lower cytotoxicity and higher gene expression than the non-reducible nanopolyplexes in cancer cells.

Photosensitizer-mediated mitochondria-targeting nanosized drug carriers: Subcellular targeting, therapeutic, and imaging potentials.

Mitochondria-targeting drug carriers have considerable potential because of the presence of many molecular drug targets in the mitochondria and their pivotal roles in cellular viability, metabolism, maintenance, and death. To compare the mitochondria-targeting abilities of triphenylphosphonium (TPP) and pheophorbide a (PhA) in nanoparticles (NPs), this study prepared mitochondria-targeting NPs using mixtures of methoxy poly(ethylene glycol)-(SS-PhA)2 [mPEG-(SS-PhA)2 or PPA] and TPP-b-poly(ε-caprolactone)-b-TPP [TPP-b-PCL-b-TPP or TPCL], which were designated PPAn-TPCL4-n (0≤n≤4) NPs. With increasing TPCL content, the formed PPAn-TPCL4-n NPs decreased in size from 33nm to 18nm and increased in terms of positive zeta-potentials from -12mV to 33mV. Although the increased TPCL content caused some dark toxicity of the PPAn-TPCL4-n NPs due to the intrinsic positive character of TPCL, the NPs showed strong light-induced killing effects in tumor cells. In addition, the mitochondrial distribution of the PPAn-TPCL4-n NPs was analyzed and imaged by flow cytometry and confocal microscopy, respectively. Thus, the PhA-containing NPs specifically targeted the mitochondria, and light stimulation caused PhA-mediated therapeutic effects and imaging functions. Expanding the capabilities of these nanocarriers by incorporating other drugs should enable multiple potential applications (e.g., targeting, therapy, and imaging) for combination and synergistic treatments.

Synthesis and characterization of a new photo-crosslinkable glycol chitosan thermogel for biomedical applications.

The major limitations of typical thermogelling polymers for practical applications are low gel stability and weak mechanical properties under physiological conditions. In this study, we have synthesized a new polysaccharide-based thermogelling polymer that can be photo-crosslinked by UV irradiation to form a mechanically resilient and elastic hydrogel. Methacrylated hexanoyl glycol chitosan (M-HGC), was synthesized by a series of chemical modifications, N-hexanoylation and N-methacrylation, of glycol chitosan (GC). Various M-HGC polymers with different methacryl group contents were synthesized and their thermogelling and photo-crosslinkable properties were evaluated. The M-HGCs demonstrated a thermo-reversible sol-gel transition behavior in aqueous solutions. The thermally-induced hydrogels could be chemically crosslinked by UV-triggered photo-crosslinking. From the cytotoxicity studies using MTT and the live/dead assay, the M-HGC hydrogels showed non-cytotoxicity. These photo-crosslinkable thermogelling M-HGC polymers may hold great promises for various biomedical applications, such as an injectable delivery system and 3D cell culture.

Hydrotropic polymer micelle system for delivery of paclitaxel.

Hydrotropic polymer micelle system has been developed for delivery of poorly water-soluble drugs such as paclitaxel. Hydrotropic polymers based on N,N-diethylnicotinamide were synthesized and used as a hydrophobic block for constructing amphiphilic block copolymers. The hydrotropic block copolymers self-assembled to form micelles in aqueous media. The size of the prepared polymer micelles was in the range of 30-50 nm, and increased to 100-120 nm after paclitaxel loading. The critical micelle concentrations (CMCs) of the block copolymers were higher by an order of magnitude than those of other typical polymer micelles, due to less hydrophobicity of the hydrotropic blocks. The drug loading capacity and physical stability of the polymer micelles were characterized and compared with those of other polymer micelles. The hydrotropic polymer micelles containing hydrotrope-rich cores showed not only higher loading capacity but also enhanced physical stability in aqueous media. They could be redissolved in aqueous media by simple vortexing and/or a mild heating. The hydrotropic polymer micelles provide an alternative approach for formulation of poorly soluble drugs.

Polyelectrolyte nanocomplex formation of heparin-photosensitizer conjugate with polymeric scavenger for photodynamic therapy.

A polyelectrolyte nanocomplex was prepared via the ionic interaction between the anionic heparin-pheophorbide a (HPhA) conjugate, which served as a water-soluble polysaccharide photosensitizer (PS), and the cationic polyethylenimine (PEI)-ß-carotene (PCAR) conjugate, which served as a polymeric scavenger. This nanocomplex was designed to improve the water solubility and tumor specificity of PhA and to only release singlet oxygen at the tumor cell. A stable 150 nm-sized nanocomplex could be formed in the weight ratio range (PCAR/HPhA) of 0.3-0.5 in an aqueous environment. The PCAR scavenger significantly diminished the generation of active singlet oxygen from HPhA in a buffer solution. Singlet oxygen scavenging activity was lost only when HPhA and PCAR were separated from each other due to the dissociation of the complex nanostructures. It was confirmed that HPhA itself has neither colloidal properties nor a decrease in its ability to produce singlet oxygen. At the same time, the HPhA/PEI complex produced singlet oxygen in response to light. In a cell culture system, the cytotoxicity of the HPhA/PCAR nanocomplex toward cancer cells was greatly enhanced due to the efficient generation of singlet oxygen under light irradiation; this finding implies that the scavenging activity of PCAR can be restricted to intracellular environments. These results suggest that the HPhA/PCAR nanocomplex could provide a new activatable PS platform that facilitates more accurate and reliable photodynamic therapy (PDT) with site-specific and controllable production of singlet oxygen to be used for the treatment of cancer.