Bone-targeting poly(ethylene sodium phosphate)

Effect of phosphodiester composition in polyphosphoesters on the inhibition of osteoclastic differentiation of murine bone marrow mononuclear cells

Osteoporosis is a common bone disorder characterized by reduced bone density and increased risk of fractures. The modulation of bone cell functions, particularly the inhibition of osteoclastic differentiation, plays a crucial role in osteoporosis treatment. Polyphosphoesters (PPEs) have shown the potential in reducing the function of osteoclast cells, but the effect of their chemical structure on osteoclastic differentiation remains largely unexplored. In this study, we evaluated the effect of PPE's chemical structure on the inhibition of osteoclastic differentiation of murine bone marrow mononuclear cells (BMNCs). PPEs containing phosphotriester and phosphodiester units at varying compositions were synthesized. Cytotoxicity testing confirmed the biocompatibility of the copolymers at concentrations below 0.5 mg/mL. Isolated from long bones, BMNCs were cultured in a differentiation medium supplemented with different PPE concentrations. Osteoclast formation was assessed through tartrate-resistant acid phosphatase and phalloidin staining. A significant decrease in the size of osteoclast cells formed upon BMNC contact with PPEs was observed, with a more pronounced effect observed at higher PPE concentrations. In addition, an increased composition of phosphodiester units in the PPEs yielded a decreased density of differentiated osteoclasts. Furthermore, real-time PCR analysis of major osteoclastic markers provided gene expression data that correlated with microscopic observations, confirming the effect of phosphodiester units in suppressing osteoclast differentiation of BMNCs from the early stages. These findings highlight the potential of PPEs as polymers are capable of modulating bone cell functions through their chemical structures.

Crystalline Micro-Sized Carbonated Apatites: Chemical Anisotropy of the Crystallite Surfaces, Biocompatibility, Osteoconductivity, and Osteoinductive Effect Enhanced by Poly(ethylene phosphoric acid)

Carbonated hydroxyapatites (CAp) are very close to natural bone apatite in chemical composition and are regarded as a prospective bone mineral substitute for bone surgery and orthopedics. However, until now, the studies and applications of CAp were limited because of the amorphous nature of the synthetic CAp. In the present work, microsized highly crystalline carbonated apatites with uniform hexagonal (hCAp) or platelike (pCAp) morphology have been studied for the first time in vitro and in vivo, comparing against commercial hydroxyapatite (HAp) and β-tricalcuim phosphate (βTCP). In vitro experiments on dissolution of those calcium phosphate ceramics (CPCs) in acetate (pH 5.5) and Tris (pH 7.3) buffer solutions showed the following rank order of the dissolution rates: βTCP > hCAp > pCAp > HAp. The higher dissolution rate of hCAp in comparison with pCAp is explained by chemical anisotropy of the crystallite surfaces, which was proven by SEM studies of the changes in the morphology of hCAp and pCAp crystallites during hydrolysis. A 5-week experiment on subcutaneous implantation of CPC species showed the following rank order of bioresorption rates: βTCP > pCAp > hCAp > HAp. pCAp matrixes exhibited the highest biocompatibility, confirmed by histomorphological analysis. Three-month bone regeneration experiments involving a rat tibial defect model were conducted with 250-500 μm granules of pCAp and pCAp-PEPA [pCAp, pretreated with 2 wt % poly(ethylene phosphoric acid)]. Notably, pCAp-PEPA implants were resorbed at higher rates and induced the formation of more mature osseous tissue, a compact bone with Haversian systems.

Dispersant and Protective Roles of Amphiphilic Poly(ethylene phosphate) Block Copolymers in Polyester/Bone Mineral Composites

Composites of synthetic bone mineral substitutes (BMS) and biodegradable polyesters are of particular interest for bone surgery and orthopedics. Manufacturing of composite scaffolds commonly uses mixing of the BMS with polymer melts. Melt processing requires a high homogeneity of the mixing, and is complicated by BMS-promoted thermal degradation of polymers. In our work, poly(L-lactide) (PLLA) and poly(ε-caprolactone) (PCL) composites reinforced by commercial β-tricalcium phosphate (βTCP) or synthesized carbonated hydroxyapatite with hexagonal and plate-like crystallite shapes (hCAp and pCAp, respectively) were fabricated using injection molding. pCAp-based composites showed advanced mechanical and thermal characteristics, and the best set of mechanical characteristics was observed for the PLLA-based composite containing 25 wt% of pCAp. To achieve compatibility of polyesters and pCAp, reactive block copolymers of PLLA or PCL with poly(tert-butyl ethylene phosphate) (C1 and C2, respectively) were introduced to the composite. The formation of a polyester-b-poly(ethylene phosphoric acid) (PEPA) compatibilizer during composite preparation, followed by chemical binding of PEPA with pCAp, have been proved experimentally. The presence of 5 wt% of the compatibilizer provided deeper homogenization of the composite, resulting in a marked increase in strength and moduli as well as a more pronounced nucleation effect during isothermal crystallization. The use of C1 increased the thermal stability of the PLLA-based composite, containing 25 wt% of pCAp. In view of positive impacts of polyester-b-PEPA on composite homogeneity, mechanical characteristics, and thermal stability, polyester-b-PEPA will find application in the further development of composite materials for bone surgery and orthopedics.

Bone-targeting polyphosphodiesters that promote osteoblastic differentiation

Polymers for pharmaceutical use have been attractive in medical treatments because of the conjugation of multifunctional components and their long circulation time in the blood stream. Bone-targeted drug delivery systems are also no exceptional, and several polymers have been proposed for the treatment of bone diseases, such as cancer metastasis and osteoporosis. Herein, we report that polyphosphodiesters (PPDEs) have a potential to enhance osteoblastic differentiation, and they have a targeting ability to bone tissues in vivo. Two types of PPDEs, poly (ethylene sodium phosphate) (PEP•Na) and poly (propylene sodium phosphate) (PPP•Na), have been synthesized. Regardless of the alkylene structure in the main chain of PPDEs, the gene expression of osteoblast-specific transcription factors and differentiation markers of mouse osteoblastic-like cells (MC3T3-E1 cells) cultured in a differentiation medium was significantly upregulated by the addition of PPDEs. Moreover, it was also clarified that the signaling pathway related to cytoplasmic calcium ions was activated by PPDEs. The mineralization of MC3T3-E1 cells has a similar trend with its gene expression and is synergistically enhanced by PPDEs with β-glycerophosphate. The biodistribution of fluorescence-labeled PPDEs was also determined after intravenous injection in mice. PPDEs accumulated well in the bone through the blood stream, whereas polyphosphotriesters (PPTEs) tended to be excreted from the kidneys. Hydrophilic PEP•Na showed a superior bone affinity as compared with PPP•Na. PPDEs could be candidate polymers for the restoration of bone remodeling and bone-targeting drug delivery platforms.

Design, Synthesis and Actual Applications of the Polymers Containing Acidic P-OH Fragments: Part 1. Polyphosphodiesters

Among natural and synthetic polymers, main-chain phosphorus-containing polyacids (PCPAs) (polyphosphodiesters), stand in a unique position at the intersection of chemistry, physics, biology and medicine. The structural similarity of polyphosphodiesters PCPAs to natural nucleic and teichoic acids, their biocompatibility, mimicking to biomolecules providing the 'stealth effect', high bone mineral affinity of polyphosphodiesters resulting in biomineralization at physiological conditions, and adjustable hydrolytic stability of polyphosphodiesters are the basis for various biomedical, industrial and household applications of this type of polymers. In the present review, we discuss the synthesis, properties and actual applications of polyphosphodiesters.

Cancer bone metastases and nanotechnology-based treatment strategies

INTRODUCTION

Bone metastases have gradually been recognized as common metastases that affect patient quality of life and survival due to the increased incidence of primary tumors. However, there is still a lack of effective clinical treatment methods for bone metastases because of their particularity and complexity. Nanomedicine provides a new strategy for the treatment of bone metastases and shows great therapeutic potential. Thus, it is important to review the latest nanomedicine treatments for bone metastases.

AREAS COVERED

This review introduces the mechanistic relationships of bone metastases and summarizes nanotechnology-based treatments of bone metastases according to targeting strategies.

EXPERT OPINION

As we start to understand the mechanisms that enable bone metastases, we can better develop nanomedicine treatments. However, many of the mechanisms behind bone metastasis remain unclear. The application of nanomedicine shows promising anti-bone metastasis efficacy and helps to explore the pathogenesis of bone metastases. The optimized construction of nanomedicine according to bone metastatic properties is crucial to ensure the desired anti-bone metastasis efficacy and good biosafety. Therefore, the transition from bench to bedside still requires continued exploration.

Controlled biointerfaces with biomimetic phosphorus-containing polymers

Phosphorus is a ubiquitous and one of the most common elements found in living organisms. Almost all molecules containing phosphorus in our body exist as analogs of phosphate salts or phosphoesters. Their functions are versatile and important, being responsible for forming the genetic code, cell membrane, and mineral components of hard tissue. Several materials inspired from these phosphorus-containing biomolecules have been recently developed. These materials have shown unique properties at the biointerface, such as nonfouling ability, blood compatibility, lubricity, mineralization induction capability, and bone affinity. Several unfavorable events occur at the interface of materials and living organisms because most of these materials have not been designed while taking host responses into account. These unfavorable events are directly linked to reducing functions and shorten the usable periods of medical devices. Biomimetic phosphorus-containing polymers can improve the reliability of materials in biological systems. In addition, phosphorus-containing biomimetic polymers are useful not only for improving the biocompatibility of material surfaces but also for adding new functions due to the flexibility in molecular design. In this review, we describe the recent advances in the control of biointerfacial phenomena with phosphorus-containing polymers. We especially focus on zwitterioninc phosphorylcholine polymers and polyphosphoesters.

Cyclic ethylene phosphates with (CH2)nCOOR and CH2CONMe2 substituents: synthesis and mechanistic insights of diverse reactivity in aryloxy-Mg complex-catalyzed (co)polymerization

Herein we present a comparative study of the reactivity of ethylene phosphates with –O(CH2)nCOOMe (n = 1–3, 5), –CH2COOtBu, –OCHMeCOOMe, and –OCH2CONMe2 substituents in BHT-Mg catalyzed ROP.

A New Approach to Developing Long-Acting Injectable Formulations of Anti-HIV Drugs: Poly(Ethylene Phosphoric Acid) Block Copolymers Increase the Efficiency of Tenofovir against HIV-1 in MT-4 Cells

Despite the world’s combined efforts, human immunodeficiency virus (HIV), the causative agent of AIDS, remains one of the world’s most serious public health challenges. High genetic variability of HIV complicates the development of anti-HIV vaccine, and there is an actual clinical need for increasing the efficiency of anti-HIV drugs in terms of targeted delivery and controlled release. Tenofovir (TFV), a nucleotide-analog reverse transcriptase inhibitor, has gained wide acceptance as a drug for pre-exposure prophylaxis or treatment of HIV infection. In our study, we explored the potential of tenofovir disoproxil (TFD) adducts with block copolymers of poly(ethylene glycol) monomethyl ether and poly(ethylene phosphoric acid) (mPEG-b-PEPA) as candidates for developing a long-acting/controlled-release formulation of TFV. Two types of mPEG-b-PEPA with numbers of ethylene phosphoric acid (EPA) fragments of 13 and 49 were synthesized by catalytic ring-opening polymerization, and used for preparing four types of adducts with TFD. Antiviral activity of [mPEG-b-PEPA]TFD or tenofovir disoproxil fumarate (TDF) was evaluated using the model of experimental HIV infection in vitro (MT-4/HIV-1_IIIB). Judging by the values of the selectivity index (SI), TFD exhibited an up to 14-fold higher anti-HIV activity in the form of mPEG-b-PEPA adducts, thus demonstrating significant promise for further development of long-acting/controlled-release injectable TFV formulations.

Particle-stabilized oil-in-water emulsions as a platform for topical lipophilic drug delivery

Low-environmental-impact emulsion systems for transdermal drug delivery in topical treatment have gained increasing interest. However, low stability and adverse systemic side effects severely decrease their efficiency. This study proposed a stable oil-in-water (O/W) emulsion loaded with bifonazole (BFZ) as a lipophilic drug stabilized by poly(2-isopropoxy-2-oxo-1,3,2-dioxaphospholane)-modified cellulose nanocrystals (CNC-g-PIPP) as vehicles for topical delivery of lipophilic drugs. We fully characterized stability, BFZ-loaded particle-stabilized emulsions (PEs) for morphology, droplet size, and its distribution. In addition, we evaluated the in vitro drug-releasing capacity and in vitro skin permeation of BFZ in a porcine skin animal model using a side-bi-side® diffusion cell. An O/W BFZ-loaded emulsion stabilized with CNC-g-PIPP particles (BFZ-loaded CP-PE) with a small mean droplet size of 2.54 ± 1.39 μm was developed and was stable for > = 15 days without a significant change in droplet size. The BFZ-loading efficiency in PEs was 83.1 %. BFZ was slowly released over an extended period, and the releasing ratio from BFZ-loaded CP-PE was only 17 % after 48 h. The BFZ-loaded CP-PE showed a ∼4.4-fold increase in BFZ permeation and penetration compared to a conventional surfactant-stabilized emulsion and BFZ control solution. Fluorescence-labeling studies showed that BFZ-loaded CP-PE could well penetrate skin layers from the stratum corneum (SC) to the dermis. In addition, histopathology studies of porcine skin treated with the PE formulation showed an intact SC with unaltered adjacent structures and no observed signs of inflammation. Therefore, the proposed CP-PE shows great potential as a transdermal drug carrier for enhancing lipophilic drug permeation.

Targeting nanoparticles for diagnosis and therapy of bone tumors: Opportunities and challenges

A variety of targeted nanoparticles were developed for the diagnosis and therapy of orthotopic and metastatic bone tumors during the past decade. This critical review will focus on principles and methods in the design of these bone-targeted nanoparticles. Ligands including bisphosphonates, aspartic acid-rich peptides and synthetic polymers were grafted on nanoparticles such as PLGA nanoparticles, liposomes, dendrimers and inorganic nanoparticles for bone targeting. Besides, other ligands such as monoclonal antibodies, peptides and aptamers targeting biomarkers on tumor/bone cells were identified for targeted diagnosis and therapy. Examples of targeted nanoparticles for the early detection of bone metastatic tumors and the ablation of cancer via chemotherapy, photothermal therapy, gene therapy and combination therapy will be intensively reviewed. The development of multifunctional nanoparticles to break down the "vicious" cycle between tumor cell proliferation and bone resorption, and the challenges and perspectives in this area will be discussed.

Selection and identification of a novel bone-targeting peptide for biomedical imaging of bone

The global burden of bone-related diseases is increasing in the aging society; thus, improved bone targeted imaging for their early identification and treatment are needed. In this study, we screened novel peptide ligands for hydroxyapatite, a major inorganic component of teeth and bones, and identified a peptide enabling in vivo bone targeting and real-time fluorescence bone detection. To isolate peptides highly specific for hydroxyapatite, we used negative and positive selection from a randomized 8-mer peptide phage library and identified hydroxyapatite-specific peptides (HA-pep2, HA-pep3, and HA-pep7). Among these three peptides, HA-pep3 showed the highest binding capacity and superior dissociation constant towards hydroxyapatite surfaces over time (~ 88.3% retained on hydroxyapatite after two weeks). Furthermore, HA-pep3 was highly specific for hydroxyapatite compared to other calcium salt-based materials. Using this superior specificity, HA-pep3 showed higher accumulation in skull, spine, and joints in comparison with scrambled control peptide during real-time whole-body imaging. Ex vivo analysis of the major organs and bone from mice demonstrated that the fluorescence intensity in bone was about 3.32 folds higher in the case of HA-pep3 than the one exhibited by the scrambled control peptide. Our study identified a novel approach for targeting ligands for bone specific imaging and can be useful for drug delivery applications.

Bone-targeting phospholipid polymers to solubilize the lipophilic anticancer drug

Current chemotherapy methods have limited effectiveness in eliminating bone metastasis, which leads to a poor prognosis associated with severe bone disorders. To provide regional chemotherapy for this metastatic tumor, a bone-targeting drug carrier was produced by introducing the osteotropic bisphosphonate alendronate (ALN) units into an amphiphilic phospholipid polymer, poly(2-methacryloyloxyethyl phosphorylcholine-co-n-butyl methacrylate). The polymer can form nanoparticles with a diameter of less than 30 nm; ALN units were exposed to the outer layer of the particle. A simple mixing procedure was used to encapsulate a hydrophobic anticancer drug, known as docetaxel (DTX), in the polymer nanoparticle, providing a uniform solution of a polymer-DTX complex in the aqueous phase. The complex showed anticancer activities against several breast cancer cell lines, and the complex formation did not hamper the pharmacological effect of DTX. The fluorescence observations evaluated by an in vivo imaging system and fluorescence microscopy showed that the addition of ALN to the polymer-DTX complex enhanced bone accumulation. Bone-targeting phospholipid polymers are potential solubilizing excipients used to formulate DTX and deliver the hydrophobic drug to bone tissues by blood administration.

Bone Mineral Affinity of Polyphosphodiesters

Biomimetic molecular design is a promising approach for generating functional biomaterials such as cell membrane mimetic blood-compatible surfaces, mussel-inspired bioadhesives, and calcium phosphate cements for bone regeneration. Polyphosphoesters (PPEs) are candidate biomimetic polymer biomaterials that are of interest due to their biocompatibility, biodegradability, and structural similarity to nucleic acids. While studies on the synthesis of PPEs began in the 1970s, the scope of their use as biomaterials has increased in the last 20 years. One advantageous property of PPEs is their molecular diversity due to the presence of multivalent phosphorus in their backbones, which allows their physicochemical and biointerfacial properties to be easily controlled to produce the desired molecular platforms for functional biomaterials. Polyphosphodiesters (PPDEs) are analogs of PPEs that have recently attracted interest due to their strong affinity for biominerals. This review describes the fundamental properties of PPDEs and recent research in the field of macromolecular bone therapeutics.

Biomaterial-assisted local and systemic delivery of bioactive agents for bone repair

Although bone tissues possess an intrinsic capacity for repair, there are cases where bone healing is either impaired or insufficient, such as fracture non-union, osteoporosis, osteomyelitis, and cancers. In these cases, treatments like surgical interventions are used, either alone or in combination with bioactive agents, to promote tissue repair and manage associated clinical complications. Improving the efficacy of bioactive agents often requires carriers, with biomaterials being a pivotal player. In this review, we discuss the role of biomaterials in realizing the local and systemic delivery of biomolecules to the bone tissue. The versatility of biomaterials enables design of carriers with the desired loading efficiency, release profile, and on-demand delivery. Besides local administration, systemic administration of drugs is necessary to combat diseases like osteoporosis, warranting bone-targeting drug delivery systems. Thus, chemical moieties with the affinity towards bone extracellular matrix components like apatite minerals have been widely utilized to create bone-targeting carriers with better biodistribution, which cannot be achieved by the drugs alone. Bone-targeting carriers combined with the desired drugs or bioactive agents have been extensively investigated to enhance bone healing while minimizing off-target effects. Herein, these advancements in the field have been systematically reviewed. STATEMENT OF SIGNIFICANCE: Drug delivery is imperative when surgical interventions are not sufficient to address various bone diseases/defects. Biomaterial-assisted delivery systems have been designed to provide drugs with the desired loading efficiency, sustained release, and on-demand delivery to enhance bone healing. By surveying recent advances in the field, this review outlines the design of biomaterials as carriers for the local and systemic delivery of bioactive agents to the bone tissue. Particularly, biomaterials that bear chemical moieties with affinity to bone are attractive, as they can present the desired bioactive agents to the bone tissue efficiently and thus enhance the drug efficacy for bone repair.

Phosphodiester Hydrogels for Cell Scaffolding and Drug Release Applications

Given the major structural role phosphodiesters play in the organism it is surprising they have not been more widely adopted as a building block in sophisticated biomimetic hydrogels and other biomaterials. The potential benefits are substantial: phosphoester-based materials show excellent compatibility with blood, cells, and a remarkable resistance to protein adsorption that may trigger a foreign-body response. In this work, a novel class of phosphodiester-based ionic hydrogels is presented which are crosslinked via a phosphodiester moiety. The material shows good compatibility with blood, supports the growth and proliferation of tissue and presents opportunities for use as a drug release matrix as shown with fluorescent model compounds. The final gel is produced via base-induced elimination from a phosphotriester precursor, which is made by the free-radical polymerization of a phosphotriester crosslinker. This crosslinker is easily synthesized via multigram one-pot procedures out of common laboratory chemicals. Via the addition of various comonomers the properties of the final gel may be tuned leading to a wide range of novel applications for this exciting class of materials.

Immobilization of polyphosphoesters on poly(ether ether ketone) (PEEK) for facilitating mineral coating

Poly(ether ether ketone) (PEEK) is an alternative material to metals for orthopedic applications. However, the compatibility of PEEK with hard tissues needs to be improved. To address this issue, this study proposes a novel technique for PEEK surface modifications. A polyphosphodiester macromonomer (PEPMA·Na) was synthesized via the demethylation of polyphosphotriester macromonomer obtained via the ring-opening polymerization of cyclic phosphoesters using 2-hydroxypropyl methacrylamide as the initiator. The surface modification of PEEK was performed via photoinduced and self-initiated graft polymerization of PEPMA·Na without using any photoinitiators. The amount of phosphorus due to poly(PEPMA·Na) immobilized on PEEK increased with an increase in the photoirradiation time. The PEEK surface turned hydrophilic due to poly(PEPMA·Na) grafting, with almost similar advancing and receding contact angles, implying that the modified PEEK surface (PEEK-g-poly(PEPMA·Na)) was homogeneous. Specimens were mineral coated by simple static soaking in ×1.5 simulated body fluid (1.5SBF) and by an alternative process that included additional soaking steps in 200 mM CaCl₂ aq. and 200 mM K₂HPO₄ aq. before static soaking in 1.5SBF. Specimens were immersed in 1.5SBF for 28 days in simple static soaking, after which the PEEK-g-poly(PEPMA·Na) surface was completely covered with spherical cauliflower-like mineral deposits that resembled octacalcium phosphate (OCP). Their structural similarities were confirmed via X-ray diffraction (XRD), energy dispersive X-ray spectrometry (EDS), and X-ray fluorescence (XRF) analyses. However, these mineral deposits were not observed on the bare PEEK surface. Due to the additional soaking steps (alternative soaking) undertaken before the static soaking of the specimens in 1.5SBF, the mineral coating on the PEEK-g-poly(PEPMA·Na) was dramatically accelerated and the surface was fully covered with mineral deposits in only one day of soaking. The mineral deposits resulting from both the soaking processes had similar structures. Compared with bare PEEK, osteoblastic MC3T3-E1 cells proliferated more actively on mineral-coated PEEK-g-poly(PEPMA·Na). Thus, the surface immobilization of poly(PEPMA·Na) on a PEEK surface is effective for mineral coating and may be useful to provide hard-tissue compatibility on PEEK.

Thermally Assisted Generation of Protein-Poly(ethylene sodium phosphate) Conjugates with High Mineral Affinity

Protein therapeutics has recently attracted interest in various medical treatments. However, the structure and function preservation in proteins under physiological conditions is still an important issue and reliable immobilization techniques are required. In this study, the thermally assisted complexation of proteins with amphiphilic polyphosphoesters is proposed as a new methodology for their durability improvement. Amphiphilic cholesterol-terminated poly(ethylene sodium phosphate) (CH-PEP·Na) was synthesized via the organocatalytic ring-opening polymerization of 2-methoxy-2-oxo-1,3,2-dioxaphospholane initiated by cholesterol as the hydrophobic molecule and followed by demethylation and neutralization. For the protein nanocarrier preparation, a complex of the amphiphilic CH-PEP·Na with bovine serum albumin (BSA) was formed through the hydrophobic interactions between the lipophilic moieties of the protein and the cholesteryl groups of the CH-PEP·Na chains, which were induced by thermal treatment at 90 °C. The resulting complex size ranged between 27 and 51 nm, as confirmed by dynamic light scattering. The complexes dispersed in an aqueous medium exhibited a high stability in size for up to 1 month of storage. CH-PEP·Na efficiently inhibited the thermal aggregation and sedimentation of BSA, unlike poly(ethylene sodium phosphate) (PEP·Na) and cholesterol-terminated poly(ethylene glycol) (CH-PEG). In addition, CH-PEP·Na was able to protect the complexed BSA against proteolytic digestion and the BSA-CH-PEP·Na complexes well adsorbed onto hydroxyapatite even in the presence of BSA (5.5 g/dL). Hence, thermally induced protein-CH-PEP·Na complexes can be a potential tool for the development of bone and dental applications.

Acid-Triggered Polymer Backbone Degradation and Disassembly to Achieve Release of Camptothecin from Functional Polyphosphoramidate Nanoparticles

Camptothecin (CPT) is a promising anticancer drug, yet its therapeutic potential has been limited by poor water solubility and facile hydrolysis of the lactone form into an inactive carboxylate form at neutral pH. In this work, a fundamental synthetic methodology was advanced to allow for the preparation of well-defined functional polyphosphoramidate (PPA)-based block copolymers that coassembled with CPT into nanoparticles, which underwent coincident acid-triggered polymer backbone degradation, nanoparticle disassembly, and CPT release. Encapsulation of CPT by the PPA polymer inhibited premature hydrolysis of CPT at pH 7.4 and enabled accelerated CPT release at pH 5.0 (ca. 4× faster than at pH 7.4). Two degradable oxazaphospholidine monomers, with one carrying an alkyne group, were synthesized to access well-defined block PPAs (dispersity, Đ<1.2) via sequential organobase-catalyzed ring-opening polymerizations (ROP). The resulting amphiphilic block copolymers (PEOMP-b-PBYOMP) were physically loaded with CPT to achieve well-dispersed nanotherapeutics, which allowed the aqueous suspension of CPT at concentrations up to 3.2 mg/mL, significantly exceeding the aqueous solubility of the drug (<2.0 μg/mL at 37 °C). Cytotoxicity studies revealed enhanced efficacy of the CPT-loaded nanoparticles over free CPT in cancer cells and similar toxicity in normal cells.