Biomedical Engineering Reference
In-Depth Information
covalently attached VIP can be used for targeted attachment to rat breast can-
cer tissues. These are currently exploring the use of covalently prepared VIP-
SSL for imaging and targeted chemotherapy of breast cancer. In a different
study, however, HI-attached VIP is preferred for the delivery of a therapeutic
agent to inflammatory cells in animal joints with rheumatoid arthritis. 75 Thus,
more investigation is necessary to establish which mode of VIP-SSL prepara-
tion is more efficient for targeted drug delivery.
Procedure for HI loading of drug on NMs 76
To prepare the micelle NMs containing a hydrophobic drug, the dialysis
method was used. 77 The protocol was as follows.
(1) Take 200 mg of the diblock copolymer and dissolve in 10 mL of DMF
(dimethylformamide).
(2) Add 150 mg of drug papaverine-free base (PAP).
(3) Stir until dissolved at RT.
(4) Filter to remove dust particles.
(5) Dialyze for 24 h against 2 L of ultrapure water using cellulose dialysis
membrane (MW cut off: 6000-8000). Change the water once every 5 h.
(6) Filter the NP solution to eliminate the unloaded drug and aggregated par-
ticles using a 0.45-µm pore-size Teflon filter.
(7) Freeze dry to obtain dried NMs.
(8) Use the freeze-dried NMs to calculate the concentration of the solution
generated.
(9) Freeze the excess NMs solution to prevent degradation of diblock copoly-
mer. The micelle NMs that do not contain the drug are also prepared fol-
lowing the same method.
5.5   NM TARGETING FOR DRUG DELIVERY
Nanotechnology provides a highly versatile platform for exploring differ-
ent approaches to improving chemotherapy through specific tumor targeting
of drugs that has been shown to effectively improve selective localization in
human tumors in vivo of small-molecule drugs such as doxorubricin. 78 NPs
as demonstrated by nanosized liposomes target tumors spontaneously because
of the fenestrated blood vessels of the tumor that result in enhanced perme-
ability and subsequent drug retention. Furthermore, liposomes offer a platform
for active targeting by linking targeting agents to the liposome core. 79,80 In a
study recently reported by Medina et al., 81 they discovered that targeting on
liposomal SKI 243 for tumor xenografts uptake exhibited that liposomal SKI
243 remained in the blood longer and consequently exhibited a three- to six-fold
increase in uptake in the tumor among several other organs.
Targeting of NMs as drug delivery vehicles or nanocarriers for site-specific
delivery has a number of advantages over targeting ligand-drug conjugates. 82
First, efficient drug loading of high concentrations of drug within the nanocarrier
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