Dendritic Poly(ethylene glycol) Bearing Paclitaxel and Alendronate for Targeting Bone Neoplasms

Nanoparticles for the Treatment of Bone Metastasis in Breast Cancer: Recent Advances and Challenges

Although the frequency of bone metastases from breast cancer has increased, effective treatment is lacking, prompting the development of nanomedicine, which involves the use of nanotechnology for disease diagnosis and treatment. Nanocarrier drug delivery systems offer several advantages over traditional drug delivery methods, such as higher reliability and biological activity, improved penetration and retention, and precise targeting and delivery. Various nanoparticles that can selectively target tumor cells without causing harm to healthy cells or organs have been synthesized. Recent advances in nanotechnology have enabled the diagnosis and prevention of metastatic diseases as well as the ability to deliver complex molecular "cargo" particles to metastatic regions. Nanoparticles can modulate systemic biodistribution and enable the targeted accumulation of therapeutic agents. Several delivery strategies are used to treat bone metastases, including untargeted delivery, bone-targeted delivery, and cancer cell-targeted delivery. Combining targeted agents with nanoparticles enhances the selective delivery of payloads to breast cancer bone metastatic lesions, providing multiple delivery advantages for treatment. In this review, we describe recent advances in nanoparticle development for treating breast cancer bone metastases.

Brief review: Applications of nanocomposite in electrochemical sensor and drugs delivery

The recent advancement of nanoparticles (NPs) holds significant potential for treating various ailments. NPs are employed as drug carriers for diseases like cancer because of their small size and increased stability. In addition, they have several desirable properties that make them ideal for treating bone cancer, including high stability, specificity, higher sensitivity, and efficacy. Furthermore, they might be taken into account to permit the precise drug release from the matrix. Drug delivery systems for cancer treatment have progressed to include nanocomposites, metallic NPs, dendrimers, and liposomes. Materials’ mechanical strength, hardness, electrical and thermal conductivity, and electrochemical sensors are significantly improved using nanoparticles (NPs). New sensing devices, drug delivery systems, electrochemical sensors, and biosensors can all benefit considerably from the NPs’ exceptional physical and chemical capabilities. Nanotechnology is discussed in this article from a variety of angles, including its recent applications in the medical sciences for the effective treatment of bone cancers and its potential as a promising option for treating other complex health anomalies via the use of anti-tumour therapy, radiotherapy, the delivery of proteins, antibiotics, and vaccines, and other methods. This also brings to light the role that model simulations can play in diagnosing and treating bone cancer, an area where Nanomedicine has recently been formulated. There has been a recent uptick in using nanotechnology to treat conditions affecting the skeleton. Consequently, it will pave the door for more effective utilization of cutting-edge technology, including electrochemical sensors and biosensors, and improved therapeutic outcomes.

A technical note on emerging combination approach involved in the onconanotherapeutics

Cancer is the second cause of mortality worldwide, and the currently available conventional treatment approach is associated with serious side effects and poor clinical outcomes. Based on the outcome of the exploratory preclinical and clinical studies, it was found that therapeutic response increases multiple folds when anticancer drugs are used in combination. However, the conventional combination of anticancer drugs was associated with various limitations such as increased cost of treatment, systemic toxicity, drug resistance, and reduced pharmacokinetic attributes. Hence, attempts were made to formulate nanocarrier fabricated combinatorial drugs (NFCDs) to effectively manage and treat cancer. This approach offers several advantages, such as improved stability, lower drug exposure, targeted drug delivery, low side effects, and improved clinical outcome. Hence, in this review, first time, we have discussed the recent advancement and various types of nano carrier-based combinatorial drug delivery systems in a different type of cancer and highlighted the personalized combinatorial theranostic medicine as a futuristic anticancer treatment approach.

Emerging concepts in designing next-generation multifunctional nanomedicine for cancer treatment

Nanotherapy has emerged as an improved anticancer therapeutic strategy to circumvent the harmful side effects of chemotherapy. It has been proven to be beneficial to offer multiple advantages, including their capacity to carry different therapeutic agents, longer circulation time and increased therapeutic index with reduced toxicity. Over time, nanotherapy evolved in terms of their designing strategies like geometry, size, composition or chemistry to circumvent the biological barriers. Multifunctional nanoscale materials are widely used as molecular transporter for delivering therapeutics and imaging agents. Nanomedicine involving multi-component chemotherapeutic drug-based combination therapy has been found to be an improved promising approach to increase the efficacy of cancer treatment. Next-generation nanomedicine has also utilized and combined immunotherapy to increase its therapeutic efficacy. It helps in targeting tumor immune response sparing the healthy systemic immune function. In this review, we have summarized the progress of nanotechnology in terms of nanoparticle designing and targeting cancer. We have also discussed its further applications in combination therapy and cancer immunotherapy. Integrating patient-specific proteomics and biomarker based information and harnessing clinically safe nanotechnology, the development of precision nanomedicine could revolutionize the effective cancer therapy.

Craft of Co-encapsulation in Nanomedicine: A Struggle To Achieve Synergy through Reciprocity

Achieving synergism, often by combination therapy via codelivery of chemotherapeutic agents, remains the mainstay of treating multidrug-resistance cases in cancer and microbial strains. With a typical core-shell architecture and surface functionalization to ensure facilitated targeting of tissues, nanocarriers are emerging as a promising platform toward gaining such synergism. Co-encapsulation of disparate theranostic agents in nanocarriers-from chemotherapeutic molecules to imaging or photothermal modalities-can not only address the issue of protecting the labile drug payload from a hostile biochemical environment but may also ensure optimized drug release as a mainstay of synergistic effect. However, the fate of co-encapsulated molecules, influenced by temporospatial proximity, remains unpredictable and marred with events with deleterious impact on therapeutic efficacy, including molecular rearrangement, aggregation, and denaturation. Thus, more than just an art of confining multiple therapeutics into a 3D nanoscale space, a co-encapsulated nanocarrier, while aiming for synergism, should strive toward achieving a harmonious cohabitation of the encapsulated molecules that, despite proximity and opportunities for interaction, remain innocuous toward each other and ensure molecular integrity. This account will inspect the current progress in co-encapsulation in nanocarriers and distill out the key points toward accomplishing such synergism through reciprocity.

Developing Actively Targeted Nanoparticles to Fight Cancer: Focus on Italian Research

Active targeting is a valuable and promising approach with which to enhance the therapeutic efficacy of nanodelivery systems, and the development of tumor-targeted nanoparticles has therefore attracted much research attention. In this field, the research carried out in Italian Pharmaceutical Technology academic groups has been focused on the development of actively targeted nanosystems using a multidisciplinary approach. To highlight these efforts, this review reports a thorough description of the last 10 years of Italian research results on the development of actively targeted nanoparticles to direct drugs towards different receptors that are overexpressed on cancer cells or in the tumor microenvironment. In particular, the review discusses polymeric nanocarriers, liposomes, lipoplexes, niosomes, solid lipid nanoparticles, squalene nanoassemblies and nanobubbles. For each nanocarrier, the main ligands, conjugation strategies and target receptors are described. The literature indicates that polymeric nanoparticles and liposomes stand out as key tools for improving specific drug delivery to the site of action. In addition, solid lipid nanoparticles, squalene nanoparticles and nanobubbles have also been successfully proposed. Taken together, these strategies all offer many platforms for the design of nanocarriers that are suitable for future clinical translation.

A Review on Re-Packaging of Bisphosphonates Using Biomaterials

The need for bone repair and insight into new regeneration therapies as well as improvement of existing regeneration routes is constantly increasing as a direct consequence of the rise in the number of trauma victims, musculoskeletal disorders, and increased life expectancy. Bisphosphonates (BPs) have emerged as a class of drugs with proven efficacy against many bone disorders. The most recent ability of this class of drugs is being explored in its anti-cancer ability. However, despite the pharmacological success, there are certain shortcomings that have circumvented this class of the drug. The mediation of biomaterials in delivering bisphosphonates has greatly helped in overcoming some of these shortcomings. This article is focused on reviewing the benefits the bisphosphonates have provided upon getting delivered via the use of biomaterials. Furthermore, the role of bisphosphonates as a potent anticancer agent is also accounted. It is witnessed that employing engineering tools in combination with therapeutics has the potential to provide solutions to bone loss from degenerative, surgical, or traumatic processes, and also aid in accelerating the healing of large bone fractures and problematic non-union fractures. The role of nanotechnology in enhancing the efficacy of the bisphosphonates is also reviewed and innovative approaches are identified.

Folic Acid-Targeted Paclitaxel-Polymer Conjugates Exert Selective Cytotoxicity and Modulate Invasiveness of Colon Cancer Cells

Although selective tumor delivery of anticancer drugs has been sought by exploiting either passive targeting or by ligand-mediated targeting, a selective anticancer therapy remains an unmet medical need. Despite the advances which have been achieved by nanomedicines, nanosystems such as polymer-drug conjugates still miss the goal of clinical efficacy. In this study, we demonstrated that polymer-drug conjugates require a thoroughly chemical design and the right targeting agent/polymer ratio to be selective and effective towards cancer cells. In particular, two PEG conjugates carrying paclitaxel and targeted with different folic acid (FA)/PEG ratios (one or three) were investigated. The cytotoxicity study in positive (HT-29) and negative (HCT-15) FA receptor (FR)-cell lines demonstrated that the conjugates with one or three FAs were 4- or 28-fold more active in HT-29 cells, respectively. The higher activity of the 3-FA conjugate was confirmed by its strong impact on cell cycle arrest. Furthermore, FA targeting had a clear effect on migration and invasiveness of HT-29 cells, which were significantly reduced by both conjugates. Interestingly, the 3-FA conjugate showed also an improved pharmacokinetic profile in mice. The results of this study indicate that thorough investigations are needed to optimize and tune drug delivery and achieve the desired selectivity and activity towards cancer cells.

Bio-Nanocarriers for Lung Cancer Management: Befriending the Barriers

Lung cancer is a complex thoracic malignancy developing consequential to aberrations in a myriad of molecular and biomolecular signaling pathways. It is one of the most lethal forms of cancers accounting to almost 1.8 million new annual incidences, bearing overall mortality to incidence ratio of 0.87. The dismal prognostic scenario at advanced stages of the disease and metastatic/resistant tumor cell populations stresses the requisite of advanced translational interdisciplinary interventions such as bionanotechnology. This review article deliberates insights and apprehensions on the recent prologue of nanobioengineering and bionanotechnology as an approach for the clinical management of lung cancer. The role of nanobioengineered (bio-nano) tools like bio-nanocarriers and nanobiodevices in secondary prophylaxis, diagnosis, therapeutics, and theranostics for lung cancer management has been discussed. Bioengineered, bioinspired, and biomimetic bio-nanotools of considerate translational value have been reviewed. Perspectives on existent oncostrategies, their critical comparison with bio-nanocarriers, and issues hampering their clinical bench side to bed transformation have also been summarized.

A Glucuronic Acid-Palmitoylethanolamide Conjugate (GLUPEA) Is an Innovative Drug Delivery System and a Potential Bioregulator

Palmitoylethanolamide (PEA) is an endogenous anti-inflammatory lipid mediator and a widely used nutraceutical. In this study, we designed, realized, and tested a drug-carrier conjugate between PEA (the active drug) and glucuronic acid (the carrier). The conjugate, named GLUPEA, was characterized for its capability of increasing PEA levels and exerting anti-inflammatory activity both in vitro and in vivo. GLUPEA treatment, compared to the same concentration of PEA, resulted in higher cellular amounts of PEA and the endocannabinoid 2-arachidonoyl glycerol (2-AG), and increased 2-AG-induced transient receptor potential vanilloid type 1 (TRPV1) channel desensitization to capsaicin. GLUPEA inhibited pro-inflammatory monocyte chemoattractant protein 2 (MCP-2) release from stimulated keratinocytes, and it was almost as efficacious as ultra-micronized PEA at reducing colitis in dinitrobenzene sulfonic acid (DNBS)-injected mice when using the same dose. GLUPEA is a novel pro-drug able to efficiently mimic the anti-inflammatory and endocannabinoid enhancing actions of PEA.

Alendronate Sodium Intercalation in Layered Double Hydroxide/Poly (ε-caprolactone): Application in Osteoporosis Treatment

Background:

Osteoporosis is a bone disease alters the amount and variety of proteins in bone tissue and increases the potential of bone fracture. Antiresorptive therapy is one of the most popular treatment methods for osteoporosis. To reduce side effects and enhance the bioavailability of drug agents, the controlled delivery of drug is commonly utilized.

Objectives:

We investigated the controlled release of Alendronate in different composites of layered double hydroxide (LDH) using poly (ε-caprolactone) (PCL) as a matrix.

Materials and Methods:

We prepared different microsphere composites of ALD intercalated in various amounts of LDH, using PCL as a matrix. The controlled release of ALD from these composites is subsequently investigated. Samples are characterized and in vitro cell cytotoxicity, attachment, osteogenic activity including alkaline phosphatase activity and mineralization are examined using MG-63 human osteosarcoma cells.

Results:

The results showed that the release of ALD is more desirable and controlled in the samples having a higher amount of LDH incorporated into the PCL matrix. MG63 cells show a significant increase in viability, attachment, and mineralization while alkaline phosphatase activity remains almost at a constant level after 3 weeks.

Conclusions:

Overall, the findings showed that by incorporation of 15 wt% of LDH, the composite microsphere is capable of holding the antiresorptive drug longer and release it in a more controlled manner. This is an advantageous and promising characteristic for a carrier that could be used as a potential candidate for osteoporosis treatment.

Targeted nanomedicines for the treatment of bone disease and regeneration

Targeted delivery by either passive or active targeting of therapeutics to the bone is an attractive treatment for various bone related diseases such as osteoporosis, osteosarcoma, multiple myeloma, and metastatic bone tumors. Engineering novel drug delivery carriers can increase therapeutic efficacy and minimize the risk of side effects. Developmnet of nanocarrier delivery systems is an interesting field of ongoing studies with opportunities to provide more effective therapies. In addition, preclinical nanomedicine research can open new opportunities for preclinical bone-targeted drug delivery; nevertheless, further research is needed to progress these therapies towards clinical applications. In the present review, the latest advancements in targeting moieties and nanocarrier drug delivery systems for the treatment of bone diseases are summarized. We also review the regeneration capability and effective delivery of nanomedicines for orthopedic applications.

The evolution of polymer conjugation and drug targeting for the delivery of proteins and bioactive molecules

Polymer conjugation can be considered one of the leading approaches within the vast field of nanotechnology-based drug delivery systems. In fact, such technology can be exploited for delivering an active molecule, such as a small drug, a protein, or genetic material, or it can be applied to other drug delivery systems as a strategy to improve their in vivo behavior or pharmacokinetic activities such as prolonging the half-life of a drug, conferring stealth properties, providing external stimuli responsiveness, and so on. If on the one hand, polymer conjugation with biotech drug is considered the linchpin of the protein delivery field boasting several products in clinical use, on the other, despite dedicated research, conjugation with low molecular weight drugs has not yet achieved the milestone of the first clinical approval. Some of the primary reasons for this debacle are the difficulties connected to achieving selective targeting to diseased tissue, organs, or cells, which is the main goal not only of polymer conjugation but of all delivery systems of small drugs. In light of the need to achieve better drug targeting, researchers are striving to identify more sophisticated, biocompatible delivery approaches and to open new horizons for drug targeting methodologies leading to successful clinical applications. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Toxicology and Regulatory Issues in Nanomedicine > Regulatory and Policy Issues in Nanomedicine.

Architectural Change of the Shell-Forming Block from Linear to V-Shaped Accelerates Micellar Disassembly, but Slows the Complete Enzymatic Degradation of the Amphiphiles

Tuning the enzymatic degradation and disassembly rates of polymeric amphiphiles and their assemblies is crucial for designing enzyme-responsive nanocarriers for controlled drug delivery applications. The common methods to control the enzymatic degradation of amphiphilic polymers are to tune the molecular weights and ratios of the hydrophilic and hydrophobic blocks. In addition to these approaches, the architecture of the hydrophilic block can also serve as a tool to tune enzymatic degradation and disassembly. To gain a deeper understanding of the effect of the molecular architecture of the hydrophilic block, we prepared two types of well-defined PEG-dendron amphiphiles bearing linear or V-shaped PEG chains as the hydrophilic blocks. The high molecular precision of these amphiphiles, which emerges from the utilization of dendrons as the hydrophobic blocks, allowed us to study the self-assembly and enzymatic degradation and disassembly of the two types of amphiphiles with high resolution. Interestingly, the micelles of the V-shaped amphiphiles were significantly smaller and disassembled faster than those of the amphiphiles based on linear PEG. However, the complete enzymatic cleavage of the hydrophobic end groups was significantly slower for the V-shaped amphiphiles. Our results show that the V-shaped architecture can stabilize the unimer state and, hence, plays a double role in the enzymatic degradation and the induced disassembly and how it can be utilized to control the release of encapsulated or bound molecular cargo.

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.

Bone Diseases: Current Approach and Future Perspectives in Drug Delivery Systems for Bone Targeted Therapeutics

Bone diseases include a wide group of skeletal-related disorders that cause mobility limitations and mortality. In some cases, e.g., in osteosarcoma (OS) and metastatic bone cancer, current treatments are not fully effective, mainly due to low patient compliance and to adverse side effects. To overcome these drawbacks, nanotechnology is currently under study as a potential strategy allowing specific drug release kinetics and enhancing bone regeneration. Polymers, ceramics, semiconductors, metals, and self-assembled molecular complexes are some of the most used nanoscale materials, although in most cases their surface properties need to be tuned by chemical or physical reactions. Among all, scaffolds, nanoparticles (NPs), cements, and hydrogels exhibit more advantages than drawbacks when compared to other nanosystems and are therefore the object of several studies. The aim of this review is to provide information about the current therapies of different bone diseases focusing the attention on new discoveries in the field of targeted delivery systems. The authors hope that this paper could help to pursue further directions about bone targeted nanosystems and their application for bone diseases and bone regeneration.

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.

Alendronate-Modified Polymeric Micelles for the Treatment of Breast Cancer Bone Metastasis

Although the prognosis of patients with breast cancer continues to improve, breast cancer metastasis to bones remains high in incidence and challenging to manage. Here, we report the development of bone-homing alendronate (ALN)-anchored biodegradable polymeric micelles for the targeted treatment of metastatic cancer to bone. These micelles exhibited bone protective capacity including the recruitment, differentiation, and resorption activity of the osteoclasts. Encapsulation of docetaxel (DTX), the first-line chemotherapeutic for treatment of metastatic breast cancer, in ALN-modified micelles results in a sustained release, enhanced cytotoxicity, and improved pharmacokinetics. In the syngeneic animal model of late-stage disseminated breast cancer bone metastasis, the treatment with targeted DTX-loaded micelles attenuated the tumorigenesis and significantly improved animal lifespan compared to the conventional surfactant-based formulation (free DTX). These findings indicate potential applications of the osteotropic nanomedicines for bone metastasis treatment.

Emerging PEGylated non-biologic drugs

Introduction: PEGylation is a well-established technology for improving the therapeutic value of drugs by attaching polyethylene glycol (PEG). The first PEGylated enzyme products appeared on the market in the early 1990s; currently, more than 18 PEGylated products have been approved by Food and Drug Administration, which encompass various classes of drug molecules, such as enzymes, interferons, granulocyte colony-stimulating factors, hormones, antibody fragments, coagulation factors, oligonucleotide aptamers, synthetic peptides, and small organic molecules. Areas covered: While PEGylated products mainly comprise biologic drugs, such as recombinant proteins and enzymes, non-biologic drugs have recently emerged as a target for PEGylation. This review focuses on the recent development of PEGylated non-biologic drugs, such as small organic molecules, synthetic peptides, and aptamers. Expert opinion: Several PEGylated versions of anti-cancer drugs, opioid agonists, glucagon-like peptide-1 receptor agonists, and oligonucleotide aptamers are in active development stage, and it is likely that they will have a dramatic impact on the market. Although some safety concerns about PEG in clinical trials have been recently issued, PEGylation is still a commercially attractive proposition as a half-life extension technology for long-acting drug development.

Threatening cancer with nanoparticle aided combination oncotherapy

Employing combination therapy has become obligatory in cancer cases exhibiting high tumor load, chemoresistant tumor population, and advanced disease stages. Realization of this fact has now led many of the combination oncotherapies to become an integral part of anticancer regimens. Combination oncotherapy may encompass a combination of anticancer agents belonging to a similar therapeutic category or that of different therapeutic categories (e.g. chemotherapy + gene therapy). Differences in the physicochemical properties, pharmacokinetics and biodistribution pattern of different payloads are the major constraints that are faced by combination chemotherapy. Concordant efforts in the field of nanotechnology and oncology have emerged with several approaches to solve the major issues encountered by combination therapy. Unique colloidal behaviors of various types of nanoparticles and differential targeting strategies have accorded an unprecedented ability to optimize combination oncotherapeutic delivery. Nanocarrier based delivery of the various types of payloads such as chemotherapeutic agents and other anticancer therapeutics such as small interfering ribonucleic acid (siRNA), chemosensitizers, radiosensitizers, and antiangiogenic agents have been addressed in the present review. Various nano-delivery systems like liposomes, polymeric nanoparticles, polymerosomes, dendrimers, micelles, lipid based nanoparticles, prodrug based nanocarriers, polymer-drug conjugates, polymer-lipid hybrid nanoparticles, carbon nanotubes, nanosponges, supramolecular nanocarriers and inorganic nanoparticles (gold nanoparticles, silver nanoparticles, magnetic nanoparticles and mesoporous silica based nanoparticles) that have been extensively explored for the formulation of multidrug delivery is an imperative part of discussion in the review. The present review features the outweighing benefits of combination therapy over mono-oncotherapy and discusses several existent nanoformulation strategies that facilitate a successful combination oncotherapy. Several obstacles that may impede in transforming nanotechnology-based combination oncotherapy from bench to bedside, and challenges associated therein have also been discussed in the present review.

Nanoparticle-Mediated Combination Therapy: Two-in-One Approach for Cancer

Cancer represents a group of heterogeneous diseases characterized by uncontrolledgrowth and spread of abnormal cells, ultimately leading to death. Nanomedicine plays a significantrole in the development of nanodrugs, nanodevices, drug delivery systems and nanocarriers. Someof the major issues in the treatment of cancer are multidrug resistance (MDR), narrow therapeuticwindow and undesired side effects of available anticancer drugs and the limitations of anticancerdrugs. Several nanosystems being utilized for detection, diagnosis and treatment such as theranosticcarriers, liposomes, carbon nanotubes, quantum dots, polymeric micelles, dendrimers and metallicnanoparticles. However, nonbiodegradable nanoparticles causes high tissue accumulation andleads to toxicity. MDR is considered a major impediment to cancer treatment due to metastatictumors that develop resistance to chemotherapy. MDR contributes to the failure of chemotherapiesin various cancers, including breast, ovarian, lung, gastrointestinal and hematological malignancies.Moreover, the therapeutic efficiency of anticancer drugs or nanoparticles (NPs) used alone is lessthan that of the combination of NPs and anticancer drugs. Combination therapy has long beenadopted as the standard first-line treatment of several malignancies to improve the clinical outcome.Combination therapy with anticancer drugs has been shown to generally induce synergistic drugactions and deter the onset of drug resistance. Therefore, this review is designed to report andanalyze the recent progress made to address combination therapy using NPs and anticancer drugs.We first provide a comprehensive overview of the angiogenesis and of the different types of NPscurrently used in treatments of cancer; those emphasized in this review are liposomes, polymericNPs, polymeric micelles (PMs), dendrimers, carbon NPs, nanodiamond (ND), fullerenes, carbonnanotubes (CNTs), graphene oxide (GO), GO nanocomposites and metallic NPs used forcombination therapy with various anticancer agents. Nanotechnology has provided the convenienttools for combination therapy. However, for clinical translation, we need continued improvementsin the field of nanotechnology.

Bortezomib-catechol conjugated prodrug micelles: combining bone targeting and aryl boronate-based pH-responsive drug release for cancer bone-metastasis therapy

The treatment of metastatic tumors is highly desirable in clinics, which has also increased the interest in the design of nanoscale drug delivery systems. Bone metastasis is one of the most common pathways in the metastasis of breast cancer, and it is also an important cause for tumor recurrence and death. The aryl boronate group, as an acid-labile linker, has been introduced into nano-assemblies in recent years. Especially, as a proteasome inhibitor anticancer drug with a boric acid group, bortezomib can facilitate the formation of pH-sensitive aryl boric acid ester linkage with the catecholic group. In this study, bortezomib-loaded micelles with bone targeting properties were constructed for the treatment of breast cancer bone metastasis. The mixed micelles employed alendronate (ALN) as the bone-targeting ligand and encapsulated bortezomib-catechol conjugates as the cargo. In vitro and in vivo studies showed that compared with free drugs or control micelles, these prodrug micelles (ALN-NP) exhibited many favorable properties such as reduced systemic toxicity and improved therapeutic effects. Therefore, ALN-NP is promising as a nanovehicle for bone-targeting delivery of chemotherapeutic drugs. Furthermore, this study offers a novel strategy combining bone targeting and aryl boronate-based pH-responsive drug release for anti-metastasis therapy.

Scaffolds as Structural Tools for Bone-Targeted Drug Delivery

Although bone has a high potential to regenerate itself after damage and injury, the efficacious repair of large bone defects resulting from resection, trauma or non-union fractures still requires the implantation of bone grafts. Materials science, in conjunction with biotechnology, can satisfy these needs by developing artificial bones, synthetic substitutes and organ implants. In particular, recent advances in materials science have provided several innovations, underlying the increasing importance of biomaterials in this field. To address the increasing need for improved bone substitutes, tissue engineering seeks to create synthetic, three-dimensional scaffolds made from organic or inorganic materials, incorporating drugs and growth factors, to induce new bone tissue formation. This review emphasizes recent progress in materials science that allows reliable scaffolds to be synthesized for targeted drug delivery in bone regeneration, also with respect to past directions no longer considered promising. A general overview concerning modeling approaches suitable for the discussed systems is also provided.

Bone Targeted Delivery of SDF-1 via Alendronate Functionalized Nanoparticles in Guiding Stem Cell Migration

Stem cells are well-known for their great capacity for tissue regeneration. This provides a promising source for cell-based therapies in treating various bone degenerative disorders. However, the major hurdles for their application in transplantation are the poor bone marrow homing and engraftment efficiencies. Stromal cell-derived factor 1 (SDF-1) has been identified as a major stem cell homing factor. With the aims of bone targeted SDF-1 delivery and regulating MSCs migration, alendronate modified liposomal nanoparticles (Aln-Lipo) carrying SDF-1 gene were developed in this study. Alendronate modification significantly increased the mineral binding affinity of liposomes, and facilitated the gene delivery to osteoblastic cells. Up-regulated SDF-1 expression in osteoblasts triggered MSCs migration. Systemic infusion of Aln-Lipo-SDF-1 with fluorescence labeling in mice showed the accumulation in osseous tissue by biophotonic imaging. Corresponding to the delivered SDF-1, the transplanted GFP⁺ MSCs were attracted to bone marrow and contributed to bone regeneration. This study may provide a useful technique in regulating stem cell migration.

Bisphosphonate conjugation for bone specific drug targeting

Bones provide essential functions and are sites of unique biochemistry and specialized cells, but can also be sites of disease. The treatment of bone disorders and neoplasia has presented difficulties in the past, and improved delivery of drugs to bone remains an important goal for achieving effective treatments. Drug targeting strategies have improved drug localization to bone by taking advantage of the high mineral concentration unique to the bone hydroxyapatite matrix, as well as tissue-specific cell types. The bisphosphonate molecule class binds specifically to hydroxyapatite and inhibits osteoclast resorption of bone, providing direct treatment for degenerative bone disorders, and as emerging evidence suggests, cancer. These bone-binding molecules also provide the opportunity to deliver other drugs specifically to bone by bisphosphonate conjugation. Bisphosphonate bone-targeted therapies have been successful in treatment of osteoporosis, primary and metastatic neoplasms of the bone, and other bone disorders, as well as refining bone imaging. In this review, we focus upon the use of bisphosphonate conjugates with antineoplastic agents, and overview bisphosphonate based imaging agents, nanoparticles, and other drugs. We also discuss linker design potential and the current state of bisphosphonate conjugate research progress. Ongoing investigations continue to expand the possibilities for bone-targeted therapeutics and for extending their reach into clinical practice.

Drug Delivery Systems from Self-Assembly of Dendron-Polymer Conjugates †

This review highlights the utilization of dendron-polymer conjugates as building blocks for the fabrication of nanosized drug delivery vehicles. The examples given provide an overview of the evolution of these delivery platforms, from simple micellar containers to smart stimuli- responsive drug delivery systems through their design at the macromolecular level. Variations in chemical composition and connectivity of the dendritic and polymeric segments provide a variety of self-assembled micellar nanostructures that embody desirable attributes of viable drug delivery systems.

Dendrimers in combination with natural products and analogues as anti-cancer agents

For the first time, an overview of dendrimers in combination with natural products and analogues as anti-cancer agents is presented. This reflects the development of drug delivery systems, such as dendrimers, to tackle cancers. The most significant advantages of using dendrimers in nanomedicine are their high biocompatibility, good water solubility, and their entry - with or without encapsulated, complexed or conjugated drugs - through an endocytosis process. This strategy has accelerated over the years in order to develop nanosystems as nanocarriers, to decrease the intrinsic toxicity of anti-cancer agents, to decrease the drug side effects, to increase the efficacy of the treatment, and consequently to improve patient compliance.

Dendrimers in combination with natural products and analogues as anti-cancer agents

Overview of the use of dendrimers in combination with encapsulated and conjugated natural products and analogues as anti-cancer agents.

Dendrimers in combination with natural products and analogues as anti-cancer agents

Overview of the use of dendrimers in combination with encapsulated and conjugated natural products and analogues as anti-cancer agents.

Self-assembling prodrugs

Covalent modification of therapeutic compounds is a clinically proven strategy to devise prodrugs with enhanced treatment efficacies. This prodrug strategy relies on the modified drugs that possess advantageous pharmacokinetic properties and administration routes over their parent drug. Self-assembling prodrugs represent an emerging class of therapeutic agents capable of spontaneously associating into well-defined supramolecular nanostructures in aqueous solutions. The self-assembly of prodrugs expands the functional space of conventional prodrug design, affording a possible pathway to more effective therapies as the assembled nanostructure possesses distinct physicochemical properties and interaction potentials that can be tailored to specific administration routes and disease treatment. In this review, we will discuss the various types of self-assembling prodrugs in development, providing an overview of the methods used to control their structure and function and, ultimately, our perspective on their current and future potential.

Recent advances in co-delivery systems based on polymeric nanoparticle for cancer treatment

Cancer is a broad term for a class of prevalent diseases as one in three people develop cancer during their lifetime. Although, there are few success stories of cancer therapy, most of the existing medications do not lead to complete recovery. Because of the complexity of cancer, usually a single therapeutic approach is insufficient for the suppression of cancer growth and metastasis. Simultaneous loading and co-delivery of different agents with different physiochemical characteristics to the same tumors have been suggested for minimizing the dose of anticancer drugs and achieving the synergistic therapeutic impacts in cancers treatment. Intense work to develop nanotechnology-based systems as a suitable option for cancer treatment is currently underway. The purpose of this review is to provide an overview of the co-delivery systems based on polymeric nanoparticles including polymeric micelles, dendrimers, poly-d,l-lactide-co-glycolide, polyethylenimine, poly(l-lysine) and chitosan for efficacious cancer therapy.

Nano-technology based carriers for nitrogen-containing bisphosphonates delivery as sensitisers of γδ T cells for anticancer immunotherapy

Nitrogen containing bisphosphonates (N-BPs) including zoledronate (ZOL) and alendronate (ALD) inhibit farnesyl diphosphate synthase, and have been shown to have a cytotoxic affect against cancer cells as a monotherapy and to also sensitise tumour cells to destruction by γδ T cells. γδ T cells are a subset of human T lymphocytes and have a diverse range of roles in the immune system including the recognition and destruction of cancer cells. This property of γδ T cells can be harnessed for use in cancer immunotherapy through in vivo expansion or the adoptive transfer of ex vivo activated γδ T cells. The use of N-BPs with γδ T cells has been shown to have a synergistic effect in in vitro, animal and clinical studies. N-BPs have limited in vivo activity due to rapid clearance from the circulation. By encapsulating N-BPs in liposomes (L) it is possible to increase the levels of N-BPs at non-osseous tumour sites. L-ZOL and L-ALD have been shown to have different toxicological profiles than free ZOL or ALD. Both L-ALD and L-ZOL led to increased spleen weight, leucocytosis, neutrophilia and lymphocytopenia in mice after intravenous injection. L-ALD was shown to be better tolerated than L-ZOL in murine studies. Biodistribution studies have been performed in order to better understand the interaction of N-BPs and γδ T cells in vivo. Additionally, in vivo therapy studies have shown that mice treated with both L-ALD and γδ T cells had a significant reduction in tumour growth compared to mice treated with L-ALD or γδ T cells alone. The use of ligand-targeted liposomes may further increase the efficacy of this combinatory immunotherapy. Liposomes targeting the αvβ6 integrin receptor using the peptide A20FMDV2 had a greater ability than untargeted liposomes in sensitising cancer cells to destruction by γδ T cells in αvβ6 positive cancer cell lines.

Bisphosphonate-Functionalized Imaging Agents, Anti-Tumor Agents and Nanocarriers for Treatment of Bone Cancer

Bone metastases result from the invasion of primary tumors to bone. Current treatment modalities include local treatments such as surgery and radiotherapy, while systemic treatments include chemotherapy and (palliative) treatment of skeletal metastases. Nevertheless, once bone metastases have been established they remain incurable leading to morbidity and mortality. Bisphosphonates are a well-established class of drugs, which are increasingly applied in the treatment of bone cancers owing to their effective inhibition of tumor cells and suppression of bone metastases. The increased understanding of the mechanism of action of bisphosphonates on bone and tumor cells has prompted the development of novel bisphosphonate-functionalized imaging and therapeutic agents. This review provides an update on the preclinical efficacy of bisphosphonate-functionalized fluorophore, anti-tumor agents and nanocarriers for the treatment of bone metastases. After an overview of the general characteristics of bisphosphonates and their mechanisms of action, an outline is provided on the various conjugation strategies that have become available to functionalize imaging agents, anti-tumor agents and nanocarriers with bisphosphonates. Finally, the efficacy of these bisphosphonate-modified agents and carriers in preclinical studies is evaluated by reviewing their potential to target tumors and inhibit tumor growth in clinically relevant animal models for the treatment of bone cancer.

Calcium phosphate nanoparticles functionalized with alendronate-conjugated polyethylene glycol (PEG) for the treatment of bone metastasis

Because of the peculiarity of the bone microstructure, the uptake of chemotherapeutics often happens at non-targeted sites, which induces side effects. In order to solve this problem, we designed a bone-targeting drug delivery system that can release drug exclusively in the nidus of the bone. Alendronate (ALN), which has a high ability to target to hydroxyapatite, was used to fabricate double ALN-conjugated poly (ethylene glycol) 2000 material (ALN-PEG_2k-ALN). The ALN-PEG_2k-ALN was characterized using ¹H NMR and ³¹P NMR and FTIR. ALN-PEG_2k-ALN-modified calcium phosphate nanoparticles (APA-CPNPs) with an ALN targeting moiety and hydrophilic poly (ethylene glycol) arms tiled on the surface was prepared for bone-targeted drug delivery. The distribution of ALN-PEG_2k-ALN was tested by X-ray photoelectron spectroscopy. Isothermal titration calorimetry data indicated that similar to free ALN, both ALN-PEG_2k-ALN and APA-CPNPs can bind to calcium ions. The bone-binding ability of APA-CPNPs was verified via ex vivo imaging of bone fragments. An in vitro release experiment demonstrated that APA-CPNPs can release drug faster in an acid environment than a neutral environment. Cell viability experiments indicated that blank APA-CPNPs possessed excellent biocompatibility with normal cells. Methotrexate (MTX) loaded APA-CPNPs have the same ability to inhibit cancer cells as free drug at high concentrations, while they are slightly weaker at low concentrations. All of these experiments verified the prospective application of APA-CPNPs as a bone-targeting drug delivery system.

Engineered Nanomedicine with Alendronic Acid Corona Improves Targeting to Osteosarcoma

We engineered nanomedicine with the stealth corona made up of densely packed bone seeking ligand, alendronic acid. In a typical nanoconstruct, alendronic acid is conjugated with hydrophilic head moiety of phospholipid that has an ability to self-assemble with hydrophobic polymeric core through its hydrophobic long carbon-chain. Proposed nanomedicine has three distinct compartments namely; poly(l-lactic-co-glycolic acid) polymeric core acting as a drug reservoir and skeleton of the nanoconstruct, phospholipid monolayer covers the core acting as a diffusion barrier, and a densely packed alendronic acid corona acting as a stabilizer and targeting moiety. Thus engineered nanomedicine attain spherical entity with ~90 ± 6 nm having negative zeta potential, −37.7 ± 2 mV, and has an ability to load 7 ± 0.3 wt% of doxorubicin. In-vitro bone targeting efficiency of nanomedicine was studied using hydroxyapatite crystals as a bone model, and found significant accumulation of nanoparticle in the crystals. Moreover, cellular internalization studies with mouse osteosarcoma confirm the selectivity of nanomedicine when compared to its internalization in non-targeted mouse melanoma. This nanomedicine shows prolong stability in serum and deliver the drug into the cell exhibiting an IC50 of 3.7 μM. Given the strong interacting property of alendronic acid with bone, the proposed nanomedicine hold promises in delivering drug to bone microenvironment.

A self-assembling nanomedicine of conjugated linoleic acid-paclitaxel conjugate (CLA-PTX) with higher drug loading and carrier-free characteristic

The main objective of this study was to demonstrate the proof-of-principle for the hypothesis that conjugated linoleic acid-paclitaxel conjugate (CLA-PTX), a novel fatty acid modified anti-cancer drug conjugate, could self-assemble forming nanoparticles. The results indicated that a novel self-assembling nanomedicine, CLA-PTX@PEG NPs (about 105 nm), with Cremophor EL (CrEL)-free and organic solvent-free characteristics, was prepared by a simple precipitation method. Being the ratio of CLA-PTX:DSPE-PEG was only 1:0.1 (w/w), the higher drug loading CLA-PTX@PEG NPs (about 90%) possessed carrier-free characteristic. The stability results indicated that CLA-PTX@PEG NPs could be stored for at least 9 months. The safety of CLA-PTX@PEG NPs was demonstrated by the MTD results. The anti-tumor activity and cellular uptake were also confirmed in the in vitro experiments. The lower crystallinity, polarity and solubility of CLA-PTX compared with that of paclitaxel (PTX) might be the possible reason for CLA-PTX self-assembling forming nanoparticles, indicating a relationship between PTX modification and nanoparticles self-assembly. Overall, the data presented here confirm that this drug self-delivery strategy based on self-assembly of a CLA-PTX conjugate may offer a new way to prepare nanomedicine products for cancer therapy involving the relationship between anticancer drug modification and self-assembly into nanoparticles.

DOPA-based paclitaxel-loaded liposomes with modifications of transferrin and alendronate for bone and myeloma targeting

Treatment for multiple myeloma (MM) with a combined strategy of bone and tumor targeting remains a crucial technical challenge due to the incorporation of various functional components into one single system. Here, we developed dioleoyl phosphatidic acid (DOPA)-based paclitaxel (PTX)-loaded liposomes with modifications of alendronate and transferrin (Ald-/Tf-modified PTX-L), which were capable of bone affinity mediated by phosphate groups in DOPA and alendronate, and tumor targeting offered by transferrin. Ald-/Tf-modified PTX-L had clear and well-defined spherical shape with an intermediated size of 118.8 ± 4.8 nm, a highly negative surface charge of -46.9 ± 6.8 mV and a drug entrapment efficiency (DEE) of approximately 80%. When the pH was changed from pH 7.4 to pH 6.5, the accumulative release of PTX from Ald-/Tf-modified PTX-L significantly increased from 26.7 ± 3.7% to 41.7 ± 4.9%. Importantly, liposomes based on DOPA displayed an obviously stronger affinity with hydroxyapatite (HAp) than 1,2-distearoyl-sn-glycero-3-phosphoethanolamine (DSPE)-based liposomes. Compared to PTX-L, Ald-/Tf-modified PTX-L exhibited obvious improvement of cytotoxicity (IC₅₀=1.25 ± 0.09 μg/mL), significant enhancement on PTX intracellular accumulation (16.58 ± 0.62 μg/mg) and notable promotion to apoptosis induction (45.21 ± 3.10%) toward myeloma (MM1s) cells. In this study of antitumor efficacy, Ald-/Tf-modified PTX-L with bone-specific targeting showed a significant effect on extending the median survival time (48 days) and terminal survival time (> 58 days) against the MM1S-injected nude mice among all formulations. The results suggested that Ald-/Tf-modified PTX-L had potential as an efficient anticancer drug delivery system for MM therapy.

In Utero Caffeine Exposure Induces Transgenerational Effects on the Adult Heart

Each year millions of pregnant woman are exposed to caffeine, which acts to antagonize adenosine action. The long-term consequences of this exposure on the developing fetus are largely unknown, although in animal models we have found adverse effects on cardiac function. To assess if these effects are transmitted transgenerationally, we exposed pregnant mice to caffeine equivalent to 2–4 cups of coffee at two embryonic stages. Embryos (F1 generation) exposed to caffeine early from embryonic (E) day 6.5–9.5 developed a phenotype similar to dilated cardiomyopathy by 1 year of age. Embryos exposed to caffeine later (E10.5–13.5) were not affected. We next examined the F2 generation and F3 generation of mice exposed to caffeine from E10.5–13.5, as this coincides with germ cell development. These F2 generation adult mice developed a cardiac phenotype similar to hypertrophic cardiomyopathy. The F3 generation exhibited morphological changes in adult hearts, including increased mass. This report shows that in utero caffeine exposure has long-term effects into adulthood and that prenatal caffeine exposure can exert adverse transgenerational effects on adult cardiac function.

Nanoprobes for Multimodal Visualization of Bone Mineral Phase in Magnetic Resonance and Near-Infrared Optical Imaging

Imaging agents with affinity for bone can enable early detection of changes to bone mineral density, which is a hallmark of many bone-associated pathologies such as Paget's disease and osteoporosis. Here, we report the development of a polymer nanoparticle (NP)-based multimodal imaging probe that enables visualization of bone mineral phase in near-infrared (NIR) optical tomography and detection in T₂-weighted magnetic resonance imaging (MRI). Ultrasmall superparamagnetic iron oxide was first encapsulated in NPs derived by blending poly(dl-lactic-co-glycolic acid)-poly(ethylene glycol) (PLGA-PEG) with N-hydroxysuccinimide functionalized-PLGA (NHS-PLGA). Postmodification of NHS surface functionality on the NPs with alendronic acid (Aln), a bone-targeting ligand, yielded stable ultrasmall superparamagnetic iron oxide nanoparticles (USPIONs) containing NPs that exhibit good serum stability and favorable cytocompatibility. These post-Aln-modified NPs exhibit 8- to 10-fold higher affinity for synthetic and biogenic hydroxyapatite in comparison to NPs where Aln was introduced before NP formation and shorten the T₂ relaxation times in both agarose phantoms and fresh spongy bone, thus enabling the interrogation of bone mineral phase in T₂-MRI. Finally, by introducing an NIR-dye-modified PLGA during the NP formation step, NP probes that enable the visualization of bone mineral phase in both NIR optical tomography and MRI have been realized. The system presented herein meets many of the criteria for clinical translation and therefore opens new opportunities for bone imaging and targeted therapeutics.

Cell Permeating Nano-Complexes of Amphiphilic Polyelectrolytes Enhance Solubility, Stability, and Anti-Cancer Efficacy of Curcumin

Many hydrophobic drugs encounter severe bioavailability issues owing to their low aqueous solubility and limited cellular uptake. We have designed a series of amphiphilic polyaspartamide polyelectrolytes (PEs) that solubilize such hydrophobic drugs in aqueous medium and enhance their cellular uptake. These PEs were synthesized through controlled (∼20 mol %) derivatization of polysuccinimide (PSI) precursor polymer with hydrophobic amines (of varying alkyl chain lengths, viz. hexyl, octyl, dodecyl, and oleyl), while the remaining succinimide residues of PSI were opened using a protonable and hydrophilic amine, 2-(2-amino-ethyl amino) ethanol (AE). Curcumin (Cur) was employed as a representative hydrophobic drug to explore the drug-delivery potential of the resulting PEs. Unprecedented enhancement in the aqueous solubility of Cur was achieved by employing these PEs through a rather simple protocol. In the case of PEs containing oleyl/dodecyl residues, up to >65000× increment in the solubility of Cur in aqueous medium could be achieved without requiring any organic solvent at all. The resulting suspensions were physically and chemically stable for at least 2 weeks. Stable nanosized polyelectrolyte complexes (PECs) with average hydrodynamic diameters (DH) of 150-170 nm (without Cur) and 220-270 nm (after Cur loading) were obtained by using submolar sodium polyaspartate (SPA) counter polyelectrolyte. The zeta potential of these PECs ranged from +36 to +43 mV. The PEC-formation significantly improved the cytocompatibility of the PEs while affording reconstitutable nanoformulations having up to 40 wt % drug-loading. The Cur-loaded PECs were readily internalized by mammalian cells (HEK-293T, MDA-MB-231, and U2OS), majorly through clathrin-mediated endocytosis (CME). Cellular uptake of Cur was directly correlated with the length of the alkyl chain present in the PECs. Further, the PECs significantly improved nuclear transport of Cur in cancer cells, resulting in their death by apoptosis. Noncancerous cells were completely unaffected under this treatment.

Physiologic Activity of Bisphosphonates – Recent Advances

Background:

Bisphosphonates are drugs commonly used for the medication and prevention of diseases caused by decreased mineral density. Despite such important medicinal use, they display a variety of physiologic activities, which make them promising anti-cancer, anti-protozoal, antibacterial and antiviral agents.

Objective:

To review physiological activity of bisphosphonates with special emphasis on their ongoing and potential applications in medicine and agriculture.

Method:

Critical review of recent literature data.

Results:

Comprehensive review of activities revealed by bisphosphonates.

Conclusion:

although bisphosphonates are mostly recognized by their profound effects on bone physiology their medicinal potential has not been fully evaluated yet. Literature data considering enzyme inhibition suggest possibilities of far more wide application of these compounds. These applications are, however, limited by their low bioavailability and therefore intensive search for new chemical entities overcoming this shortage are carried out.

Prodrug Strategies for Paclitaxel

Paclitaxel is an anti-tumor agent with remarkable anti-tumor activity and wide clinical uses. However, it is also faced with various challenges especially for its poor water solubility and low selectivity for the target. To overcome these disadvantages of paclitaxel, approaches using small molecule modifications and macromolecule modifications have been developed by many research groups from all over the world. In this review, we discuss the different strategies especially prodrug strategies that are currently used to make paclitaxel more effective.