Effect of poly (ethylene oxide)‐poly (propylene oxide)‐poly (ethylene oxide) micelles on pharmacokinetics and intestinal toxicity of irinotecan hydrochloride: potential involvement of breast cancer resistance protein (ABCG2)

Objectives Intestinal toxicity and low levels of systemic drug exposure are among the major problems associated with tumour therapy. We have developed poly (ethylene oxide)‐poly (propylene oxide)‐poly (ethylene oxide) (PEO‐PPO‐PEO) micelles loaded with irinotecan hydrochloride (CPT‐11) hoping to decrease CPT‐11‐induced intestinal toxicity while increasing its systemic exposure. In addition, we have investigated the potential involvement of breast cancer resistance protein (BCRP) in biliary excretion, pharmacokinetics, and intestinal toxicity of CPT‐11. Methods PEO‐PPO‐PEO micelles were prepared using PEO₂₀‐PPO₇₀‐PEO₂₀ and lecithin. The effect of PEO‐PPO‐PEO micelles on BCRP‐mediated cellular accumulation and transport efflux of CPT‐11 was evaluated in MDCKII/BCRP cells. The biliary excretion, intestinal damage, and pharmacokinetic study of CPT‐11‐loaded PEO‐PPO‐PEO micelles were investigated in rats. Key findings The obtained micelles could effectively inhibit BCRP‐mediated CPT‐11 efflux in MDCKII/BCRP cells, and significantly decrease the drug biliary excretion in rats. Moreover, intestinal toxicity, assessed by microscopic examination of pathological damage, was ameliorated in rats injected with PEO‐PPO‐PEO micelles compared with rats injected with CPT‐11 alone. Treatment with PEO‐PPO‐PEO micelles resulted in prolonged circulation time in blood and increased bioavailability of CPT‐11 and SN‐38 (7‐ethyl‐10‐hydroxycamptothecin). Conclusions PEO‐PPO‐PEO micelles were identified as promising carriers able to reduce intestinal toxicity and increase antitumour therapeutic effect of CPT‐11. The study indicated a potential involvement of BCRP in CPT‐11 pharmacokinetics and CPT‐11‐induced intestinal toxicity.     

Ultrasound-responsive nanobubbles contained with peptide–camptothecin conjugates for targeted drug delivery

To improve the targeting delivery efficiency of anticancer drug to tumor sites, a new strategy combining cell-permeable peptide (CPP) and ultrasound was reported in this article. In this study, we devised and tested a strategy for functional payload delivery to cells by loading CPP–camptothecin conjugate (CPP–CPT) into nanobubble (CPP–CPT?NB). Here, CPP existing in the conjugation form of CPP and CPT was hidden in nanobubble to cloak the penetration activity of CPP. Meanwhile, local tumor ultrasound was utilized to achieve specific targeting of CPP–CPT to the tumor cells. The mean particle size of the prepared CPP–CPT?NB was ～200?nm, and the drug entrapment efficiency was >80%. Stimulated by ultrasound, over 90% of the entrapped CPP–CPTs would release from the nanobubbles. Subsequent research demonstrated that the CPP–CPT?NB showed effective cellular uptake and significant cytotoxic activity in HeLa cells in vitro. Additionally, after systemic administration in mice, CPP–CPT?NB with ultrasound showed a higher tumor inhibition effect in nude mice xenografted HeLa cells tumors and excellent body safety when compared with normal CPT injection group. In conclusion, the carrier constructed in this study would be a safe and efficiently drug delivery system for specific cancer treatment.     

Preparation of carboxy‐PEG‐PLA nanoparticles loaded with camptothecin and their body distribution in solid tumor–bearing mice

Carboxy‐polyethylene glycol‐poly(DL‐lactic acid) block copolymer was synthesized by reductive amination of carboxy‐polyethylene glycol‐amine and aldehyde‐ended poly(DL‐lactic acid). The obtained product, PA‐PEG‐CB, composed of pure carboxy‐polyethylene glycol‐poly(DL‐lactic acid) block copolymer and poly(DL‐lactic acid), was used to prepare nanoparticles loaded with camptothecin (CPT), designated CPT‐NP. CPT‐NP with 500–600 nm and approximately 1% (w/w) drug content were obtained by emulsification/evaporation, while nanoparticles with a drug content of only less than 0.1% (w/w) were prepared by dialysis. CPT‐NP produced by emulsification/evaporation were used for in vitro and in vivo studies. CPT‐NP released CPT gradually in phosphate‐buffered saline, pH 7.4, at 37°C over 48 h. Biodistribution profiles were compared between CPT‐NP and CPT solution after i.v. injection into mice bearing sarcoma 180 solid tumor. CPT‐NP retained CPT approximately 10 times more in plasma during the initial 8 h than CPT solution. The tumor level of CPT was more than 10 times higher with CPT‐NP for the observation period (24 h), though the CPT concentration in the liver and spleen was much higher with CPT‐NP. CPT‐NP may be useful for tumor localization of CPT. Drug Dev Res 70: 512–519, 2009. © 2009 Wiley‐Liss, Inc.     

Permeability of a novel β‐lactamase inhibitor LK‐157 and its ester prodrugs across rat jejunum in vitro

Objectives LK‐157 is a novel 10‐ethylidene tricyclic carbapenem that resembles the structure of the broad‐spectrum antibiotic sanfetrinem and acts as a potent inactivator of β‐lactamases of classes A, C and D. LK‐157 is a highly soluble but poorly permeable drug. Since most of the β‐lactams are poorly absorbed, ester prodrugs LK‐159, LK‐157E1 and LK‐157E2 were designed to enhance membrane permeability. This study investigated the permeability of LK‐157 and the three ester prodrugs across rat intestine in vitro. The morpholinoethyl ester of sanfetrinem was also investigated. Method Permeability across rat jejunum was determined using EasyMount side‐by‐side diffusion chambers. Key findings The solubility and permeability of morpholinoethyl ester LK‐157E2 were superior to those of LK‐159 and LK‐157E1. The morpholinoethyl ester of sanfetrinem LK‐176E1 had the highest observed permeability coefficient and consequently the highest predicted absorption in humans. Conclusions These results suggest that the morpholinoethyl esters of LK‐157 and sanfetrinem could be further investigated to assess bioavailability in vivo.     

Design of a pH‐sensitive pore‐forming peptide with improved performance

Abstract: GALA is a 30 residue synthetic peptide designed to interact with membranes in a pH‐sensitive manner, with potential applications for intracellular drug and gene delivery. Upon reduction of the pH from neutral to acidic, GALA switches from random coil to α‐helix, inserts into lipid bilayers, and forms oligomeric pores of defined size. Its simple sequence and well‐characterized behavior make the peptide an excellent starting point to explore the effects of sequence on structure, pH sensitivity, and membrane affinity. We describe synthesis and characterization of two derivatives of GALA, termed GALAdel3E and YALA. GALAdel3E has a deletion of three centrally located glutamate residues from GALA, while YALA replaces one glutamate residue with the unusual amino acid 3,5‐diiodotyrosine. Both derived peptides retain pH sensitivity, showing no ability to cause leakage of an encapsulated dye from unilamellar vesicles at pH 7.4 but substantial activity at pH 5. Unlike GALA, neither peptide undergoes a conformational change upon reduction of the pH, remaining α‐helical throughout. Interestingly, the pH at which the peptides activate is shifted, with GALA becoming active at pH ～5.7, GALAdel3E at pH ～6.2, and YALA at pH ～6.7. Furthermore, the peptides GALAdel3E and YALA show improved activity compared with GALA for cholesterol‐containing membranes, with YALA retaining the greatest activity. Improved activity in the presence of cholesterol and onset of activity in the critical range between pH 6 and 7 may make these peptides useful in applications requiring intracellular delivery of macromolecules, such as gene delivery or anti‐cancer treatments.     

Proline residue‐modified polycationic analogs of gramicidin S with high antibacterial activity against both Gram‐positive and Gram‐negative bacteria and low hemolytic activity*

Abstract: Novel polycationic analogs of the cyclic decapeptide antibiotic, gramicidin S, possessing NH₂, d /l ‐Phe‐NH or l ‐Lys‐NH groups at the 4α‐ or 4β‐positions of the l ‐Pro residues, were synthesized. While l ‐Pro(4α/β‐NH₂)‐containing analogs exhibited much weaker antibacterial activity, the d /l ‐Phe and l ‐Lys‐substituted analogs exhibited higher antibacterial activity against Gram‐negative bacteria than the parent gramicidin S. All of these additional amino group‐containing analogs showed substantially reduced toxicity against human blood cells.     

Immunocompatibility and Toxicity Studies of Poly‐L‐Lysine Nanocapsules in Sprague–Dawley Rats for Drug‐Delivery Applications

Poly‐L‐Lysine (PLL) nanocapsules are the emerging drug‐delivery vehicle for the therapeutics of targeted diseases. The study was designed for the synthesis and characterization of PLL nanocapsules and to know its immunocompatibility and toxicity behavior for in vivo drug‐delivery applications. Alteration in hematologic parameters, immunomodulatory gene expression by RT‐PCR studies, toxicity markers status, immunoblotting of major inflammatory marker proteins, and histopathologic studies from major tissues of rat after intravenous administration of PLL nanocapsules after 30 days were assessed. In vivo toxicity markers activity, hematologic parameters alteration, and RT‐PCR analysis of important immunomodulatory genes such as monocyte chemotactic protein‐1(MCP 1), tumor necrosis factor‐alpha (TNF‐α), Intercellular adhesion molecule‐1 (ICAM‐1), and interleukin‐6 (IL‐6) showed least changes when compared with control. The immunoblotting of major inflammatory markers such as cyclooxygenase‐2 (COX‐2), lipo‐oxygenase‐15 (LOX‐15), and nitric oxide synthase (NOS) found have least expression showing the immunocompatibility of PLL nanocapsules. Histopathologic studies of important tissues showed almost normal architecture after treatment using different concentration of PLL nanocapsules after the experimental period. The results showed a promising outcome and further confirmed the immunocompatibility and non‐toxicity of PLL nanocapsules in vivo for drug‐delivery applications.     

Synthesis of 3,7,8‐15N3‐N1‐(β‐D‐erythro‐pentofuranosyl)‐5‐guanidinohydantoin

3,7,8‐¹⁵N₃‐N¹‐(β‐D‐erythro‐pentofuranosyl)‐5‐guanidinohydantoin was synthesized from the oxidation of 1,7,NH₂‐¹⁵N₃‐8‐oxo‐7,8‐dihydro‐2′‐deoxyguanosine with 2 equivalents of Ir(IV) in pH 4.5 potassium phosphate buffer. The synthesis of 1,7,NH₂‐¹⁵N₃‐8‐oxo‐7,8‐dihydro‐2′‐deoxyguanosine started with bromination of 1,7,NH₂‐¹⁵N₃‐2′‐deoxyguanosine. The resulting 1,7,NH₂‐¹⁵N₃‐8‐bromo‐7,8‐dihydro‐2′‐deoxyguanosine reacted with sodium benzyloxide to afford 1,7,NH₂‐¹⁵N₃‐8‐benzyloxy‐7,8‐dihydro‐2′‐deoxyguanosine. Subsequent catalytic transfer hydrogenation of 1,7,NH₂‐¹⁵N₃‐8‐benzyloxy‐7,8‐dihydro‐2′‐deoxyguanosine with cyclohexene and 10% Pd/C yielded 1,7,NH₂‐¹⁵N₃‐8‐oxo‐7,8‐dihydro‐2′‐deoxyguanosine. Purification of 3,7,8‐¹⁵N₃‐N¹‐(β‐D‐erythro‐pentofuranosyl)‐5‐guanidinohydantoin was first carried out on a C18 column and the product was further purified on a graphite column. ESI‐MS was used to confirm the identity and to determine the isotopic purity of all the labeled compounds. The isotopic purity of 3,7,8‐¹⁵N₃‐N¹‐(β‐D‐erythro‐pentofuranosyl)‐5‐guanidinohydantoin was 99.4 atom% based on LC‐MS measurements. Copyright © 2003 John Wiley & Sons, Ltd.     

Synthesis and activity of the melanocortin Xaa‐d‐Phe‐Arg‐Trp‐NH2 tetrapeptides with amide bond modifications

Abstract: The melanocortin receptor (MCR) pathway has been identified as participating in several physiologically important pathways including pigmentation, energy homeostasis, inflammation, obesity, hypertension, and sexual function. All the endogenous MCR agonists contain a core His‐Phe‐Arg‐Trp sequence identified as important for receptor molecular recognition and stimulation. Several structure–activity studies using the Ac‐His‐d ‐Phe‐Arg‐Trp‐NH₂ tetrapeptide template have been performed in the context of modifying N‐terminal ‘capping’ groups and amino acid constituents. Herein, we report the synthesis and pharmacologic characterization of modified Xaa‐d ‐Phe‐Arg‐Trp‐NH₂ (Xaa = His or Phe) melanocortin tetrapeptides (N‐site selective methylation, permethylation, or amide bond reduction) at the mouse MC1, MC3, MC4 and MC5 receptors. The modified peptides generated in this study resulted in equipotent or reduced MCR potency when compared with control ligands. The reduced amide bond analog of the Phe‐d ‐Phe‐Arg‐Trp‐NH₂ peptide converted its agonist activity into an antagonistic at the central mMC3 and mMC4 receptors involved in the regulation of energy homeostasis, while retaining full agonist activity at the peripheral MC1 and MC5 receptors.     

Anticancer activity of VmCT1 analogs against MCF‐7 cells

Antimicrobial peptides are considered promising drug candidates due to their broad range of activity. VmCT1 (Phe–Leu–Gly–Ala–Leu–Trp–Asn–Val–Ala–Lys–Ser–Val–Phe–NH₂) is an α‐helical antimicrobial peptide that was obtained from the Vaejovis mexicanus smithi scorpion venom. Some of its analogs showed to be as antimicrobial as the wild type, and they were designed for understanding the influence of physiochemical parameters on antimicrobial and hemolytic activity. Some cationic antimicrobial peptides exhibit anticancer activity so VmCT1 analogs were tested to verify the anticancer activity of this family of peptides. The analogs were synthesized, purified, characterized, and the conformational studies were performed. The anticancer activity was assessed against MCF‐7 mammary cancer cells. The results indicated that [Glu]⁷‐VmCT1‐NH₂, [Lys]³‐VmCT1‐NH₂, and [Lys]⁷‐VmCT1‐NH₂ analogs presented moderated helical tendency (0.23–0.61) and tendency of anticancer activity at 25 μmol/L in 24 hr of experiment; and [Trp]⁹‐VmCT1‐NH₂ analog that presented low helical tendency and moderated anticancer activity at 50 μmol/L. These results demonstrated that single substitutions on VmCT1 led to different physicochemical features and could assist on the understanding of anticancer activity of this peptide family.     

Caution in the use of 2‐iminothiolane (Traut's reagent) as a cross‐linking agent for peptides. The formation of N‐peptidyl‐2‐iminothiolanes with bombesin (BN) antagonist (d‐Trp6,Leu13‐ψ[CH2NH]‐Phe14)BN6−14 and d‐Trp‐Gln‐Trp‐NH2

Abstract: During a study aimed at generating a bispecific molecule between BN antagonist (d ‐Trp⁶,Leu¹³‐ψ[CH₂NH]‐Phe¹⁴)BN_6‐14 (Antag1) and mAb22 (anti‐FcγRI), we attempted to cross‐link the two molecules by introducing a thiol group into Antag1 via 2‐iminothiolane (2‐IT, Traut's reagent). We found that reaction of Antag1 with 2‐IT, when observed using HPLC, affords two products, but that the later eluting peptide is rapidly transformed into the earlier eluting peptide. To understand what was occurring we synthesized a model peptide, d ‐Trp‐Gln‐Trp‐NH₂ (TP1), the N‐terminal tripeptide of Antag1. Reaction of TP1 with 2‐IT for 5 min gave products 1a and 3a ; the concentration of 1a decreased with reaction time, whereas that of 3a increased. Thiol 1a , the expected Traut product, was identified by collecting it in a vial containing N‐methylmaleimide and then isolating the resultant Michael addition product 2a , which was confirmed by mass spectrometry. Thiol 1a is stable at acidic pH, but is unstable at pH 7.8, cyclizes and loses NH₃ to give N‐TP1‐2‐iminothiolane ( 3a ), ES‐MS (m/z) [602.1 (M+H)⁺], as well as regenerating TP1. Repeat reaction with Antag1 and 2‐IT allowed us to isolate N‐Antag1–2‐iminothiolane ( 3b ), FAB‐MS (m/z) [1212.8 (M+H)⁺] and trap the normal Traut product 1b as its N‐methylmaleimide Michael addition product 2b , ES‐MS (m/z) [1340.8 (M+H)⁺]. Thiol 1b is also stable at acidic pH, but when neutralized is unstable and cyclizes, forming 3b and Antag1.     

Antitumour properties based on the self‐assembly of camptothecin and carbamoylmannose conjugates

Camptothecin (CPT) and its analogues show potent antitumour activity. However, poor water solubility and severe side effects have restricted their applications in clinical practice. In this paper, a novel self‐assembly based on camptothecin and carbamoylmannose conjugates ( CPT‐Man ) was constructed. The self‐assembly increased the water solubility of camptothecin to 0.64 mg/ml and antitumour activity. Moreover, CPT‐Man could induce obvious cancer cell apoptosis. This work provides a new approach for exploring carbohydrate‐modified antitumour properties by self‐assembled CPT drugs.     

Cell‐Penetrating Peptides as Carriers for Oral Delivery of Biopharmaceuticals

Oral delivery of biopharmaceuticals, for example peptides and proteins, constitutes a great challenge in drug delivery due to their low chemical stability and poor permeation across the intestinal mucosa, to a large extent limiting the mode of administration to injections, which is not favouring patient compliance. Nevertheless, cell‐penetrating peptides (CPPs) have shown promising potential as carriers to overcome the epithelium, and this minireview highlights recent knowledge gained within the field of CPP‐mediated transepithelial delivery of therapeutic peptides and proteins from the intestine. Two approaches may be pursued: co‐administration of the carrier and therapeutic peptide in the form of complexes obtained by simple bulk mixing, or administration of covalent conjugates demanding more advanced production methodologies. These formulation approaches have their pros and cons, and which is to be preferred depends on the physicochemical properties of both the specific CPP and the specific cargo. In addition to the physical epithelial barrier, a metabolic barrier must be overcome in order to obtain CPP‐mediated delivery of a cargo drug from the intestine, and a number of strategies have been employed to delay enzymatic degradation of the CPP. The mechanisms by which CPPs translocate across membranes are not fully understood, but possibly involve endocytosis as well as direct translocation, and the CPP‐mediated transepithelial delivery of cargo drugs thus likely involves similar mechanisms for the initial membrane interaction and translocation. However, the mechanisms responsible for transcytosis of the cargo drug, if taken up by an endocytic mechanism, or direct translocation across the epithelium are so far not known.     

Synthesis and in‐vitro Cytotoxicity of Poly‐functionalized 4‐(2‐Arylthiazol‐4‐yl)‐4H‐chromenes

A new series of 4‐aryl‐4H‐chromenes bearing a 2‐arylthiazol‐4‐yl moiety at the 4‐position were prepared as potential cytotoxic agents. The in‐vitro cytotoxic activity of the synthesized 4‐aryl‐4H‐chromenes was investigated in comparison with etoposide, a well‐known anticancer drug, using MTT colorimetric assay. Among them, the 2‐(2‐chlorophenyl)thiazol‐4‐yl analog 4b showed the most potent activity against nasopharyngeal epidermoid carcinoma KB, medulloblastoma DAOY, and astrocytoma 1321N1, and compound 4d bearing a 2‐(4‐chlorophenyl)thiazol‐4‐yl moiety at the 4‐position of the chromene ring exhibited the best inhibitory activity against breast cancer cells MCF‐7, lung cancer cells A549, and colon adenocarcinoma cells SW480 with IC₅₀ values less than 5 μM. The ability of compound 4b to induce apoptosis was confirmed in a nuclear morphological assay by DAPI staining in the KB and MCF‐7 cells.     

Radiosynthesis of 13N‐labeled thalidomide using no‐carrier‐added [13N]NH3

Recent studies revealed that thalidomide (1) has unique and broad pharmacological effects on multi‐targets although the application of 1 in therapy is still controversial. In this study, we synthesized nitrogen‐13‐labeled thalidomide ([¹³N]1) as a potential positron emission tomography (PET) probe using no‐carrier‐added [¹³N]NH₃ as a labeling agent. By use of an automated system, [¹³N]1 was prepared by reacting N‐phthaloylglutamic anhydride (2) with [¹³N]NH₃, following by cyclization with carbonyldiimidazole in a radiochemical yield of 56±12% (based on [¹¹N]NH₃, corrected for decay) and specific activity of 49±24 GBq/µmol at the end of synthesis (EOS). At EOS, 570–780 MBq (n=7) of [¹³N]1 was obtained at a beam current of 15 µA after 15 min proton bombardment with a synthesis time of 14 min from the end of bombardment. Using a small animal PET scanner, preliminary biodistribution of [¹³N]1 in mice was examined. Copyright © 2010 John Wiley & Sons, Ltd.     

喜树碱结构修饰与构效关系研究进展

喜树碱是从喜树提取物中分离出的能够抗细胞增殖的天然生物碱。由于其溶解性低、稳定性差和显著的不良反应限制了其临床应用,所以在过去的十余年里合成了许多喜树碱衍生物。通过引入极性基团、靶向剂或药效团拼合、前药等在喹啉环、5位和20位进行结构修饰,其中大多数与喜树碱相比显示出更强的效力,对不同的肿瘤细胞具有活性,其中许多对多药耐药肿瘤细胞具有活性。综述了近年来47个新的喜树碱衍生物的合成方法和生物活性,并总结了构效关系,发现在喹啉环和内酯环的羟基上修饰通常可以增强体外抗肿瘤活性,药物递送系统、计算机高通量筛选等新技术的应用为改善喜树碱的溶解性、稳定性,寻找活性较好的先导化合物拓展了新思路。     

Berberine‐loaded Janus nanocarriers for magnetic field‐enhanced therapy against hepatocellular carcinoma

Berberine, an bioactive isoquinolin alkaloid from traditional Chinese herbs, is considered to be a promising agent based on its remarkable activity against hepatocellular carcinoma. However, the clinical application of this nature compound had been hampered owing to its properties such as poor aqueous solubility, low gastrointestinal absorption, and reduced bioavailability. Therefore, we developed Janus magnetic mesoporous silica nanoparticles (Fe₃O₄‐mSiO₂ NPs) consisting of a Fe₃O₄ head for magnetic targeting and a mesoporous SiO₂ body for berberine delivery. A pH‐sensitive group was introduced on the surface of mesoporous silica for berberine loading to develop a tumor microenvironment‐responsive nanocarrier, which exhibited uniform morphology, good superparamagnetic properties, high drug‐loading amounts, superior endocytic ability, and low cytotoxicity. Berberine‐loaded Fe₃O₄‐mSiO₂ NPs exerted extraordinarily high specificity for hepatocellular carcinoma cells, which was due to the pH‐responsive berberine release, as well as higher endocytosis capacity in hepatocellular carcinoma cells rather than normal liver cells. More importantly, an external magnetic field could significantly improve antitumor activity of Ber‐loaded Fe₃O₄‐mSiO₂ NPs through enhancing berberine internalization. Taken together, our results suggest that Janus nanocarriers driven by the magnetic field may provide an effective and safe way to facilitate clinical use of berberine against hepatocellular carcinoma.     

Synthesis and biological evaluation of constrained analogues of the opioid peptide H‐Tyr‐d‐Ala‐Phe‐Gly‐NH2 using the 4‐amino‐2‐benzazepin‐3‐one scaffold

Abstract: The synthesis of conformationally restricted dipeptidic moieties 4‐amino‐1,2,4,5‐tetrahydro‐2‐benzazepin‐3‐one (Aba)‐Gly ([(4S)‐amino‐3‐oxo‐1,2,4,5‐tetrahydro‐1H‐2‐benzazepin‐2‐yl]‐acetic acid) and 8‐hydroxy‐4‐amino‐1,2,4,5‐tetrahydro‐2‐benzazepin‐3‐one (Hba)‐d ‐Ala ([(4S)‐amino‐8‐hydroxy‐3‐oxo‐1,2,4,5‐tetrahydro‐benzo[c]azepin‐2‐yl]‐propionic acid) was based on a synthetic strategy that uses an oxazolidinone as an N‐acyliminium precursor. Introducing these Aba scaffolds into the N‐terminal tetrapeptide of dermorphin (H‐Tyr‐d ‐Ala‐Phe‐Gly‐Tyr‐Pro‐Ser‐NH₂)‐induced remarkable shifts in affinity and selectivity towards the opioid μ‐ and δ‐receptors. This paper provides the synthesis and biological in vitro and in vivo evaluation of constricted analogues of the N‐terminal tetrapeptide H‐Tyr‐d ‐Ala‐Phe‐Gly‐NH₂, which is the minimal subunit of dermorphin needed for dermorphin‐like opiate activity.     

Topical delivery of fluorescence (6‐Cf) labeled and radiolabeled (99m‐Tc) cisplatin and imiquimod by a dual drug delivery system

The present investigation deals with the development of topical (top.) formulation for co‐delivery of cisplatin and imiquimod to enhance the antitumor efficacy of the drug for skin‐cited malignancies even in immune compromised patient. Cisplatin (CDDP) and imiquimod‐loaded protransfersome gel (CDDP‐Imi‐Pts gel) formulation was characterized for entrapment efficiency, pH, and viscosity. Further, fluorescence‐labeled (6‐carboxyfluorescin) and radiolabeled (^99mtechnetium) drug‐loaded formulations were compared with respect to biodistribution and pharmacokinetic studies. Gamma scintigraphy of mice following radiolabeled formulation administrations was performed to accomplish the localization of drugs in various organs. The percentage entrapment efficiency of cisplatin and imiquimod in the protransfersome gel formulations were found to be 36.22 ± 6.41 and 63.11 ± 3.73. The skin/blood localization ratio of 1.096, 120.13, 0.174, and 349.88 was found for intraperitoneal radiolabeled drug solution (^99m‐Tc‐CDDP‐Imi‐Sol), top. radiolabeled drug‐loaded protransfersome gel formulation (^99m‐Tc‐CDDP‐Imi‐Pts gel), intraperitoneal 6‐carboxyfluorescin labeled drug solution (6‐Cf‐CDDP‐Imi‐Sol), top. 6‐carboxyfluorescin labeled drug‐loaded protransfersome gel formulation (6‐Cf‐CDDP‐Imi‐Pts gel), respectively after 0.5h of administration. CDDP‐Imi‐Pts gel has a potential for site specific delivery and reduces the systemic toxicity of anti cancer drugs. These findings suggest that the cisplatin–imiquimod co‐delivery offers an attractive, novel approach for treatment of skin‐cited malignancies.