SCIENTIfIC RepoRTS | 7: 16803 | DOI:10.1038/s41598-017-16791-7
Characterization of liposomal
carriers for the trans-scleral
transport of Ranibizumab
Rini Rachel Joseph
, Dulcia Wei Ni Tan
, Moreno Raja Miguel Ramon
, Jayaganesh V.
, Rupesh Agrawal
, Tina T Wong
& Subbu S Venkatraman
Age-related macular degeneration (AMD) is a leading cause of blindness in the modern world. The
standard treatment regimen for neovascular AMD is the monthly/bimonthly intravitreal injection of
anti-VEGF agents such as ranibizumab or aibercept. However, these repeated invasive injections can
lead to sight-threatening complications. Sustained delivery by encapsulation of the drug in carriers is
a way to reduce the frequency of these injections. Liposomes are biocompatible, non-toxic vesicular
nanocarriers, which can be used to encapsulate therapeutic agents to provide sustained release.
The protein encapsulation was performed by a modied dehydration-rehydration (DRV) method.
The liposomes formed were characterized for size, zeta potential, encapsulation eciency, stability,
in vitro release, and ex vivo release proles. In addition, the localization of the liposomes themselves
was studied ex vivo. Entrapment-eciency of ranibizumab into 100-nm liposomes varied from 14.7
to 57.0%. Negatively-charged liposomes prepared from DPPC-DPPG were found to have the slowest
release with a low initial burst release compared to the rest of liposomal formulations. The ex vivo
protein release was found to slower than the in vitro protein release for all samples. In conclusion, the
DPPC-DPPG liposomes signicantly improved the encapsulation and release prole of ranibizumab.
For several proliferative vitreoretinal diseases in the eye, intravitreal injection of anti-VEGF drugs is the current
standard of treatment. is is an invasive procedure and may lead to sight-threatening complications such as
endophthalmitis, cataract or even retinal detachment
e periocular route of ocular drug delivery has been proposed as a less invasive alternative to the posterior
delivery with no disruption to the integrity of the eyeball
. e main barriers to trans-scleral delivery have been
classied as static, dynamic and metabolic
. Transport characteristics of several drugs and macromolecules across
the sclera have been studied over the past few decades to delineate the properties aecting the transport across
this barrier. Notably, Ambati et al. have studied the transport of several small molecules across the sclera in an
ex vivo setup to determine the size eect of these molecules on trans-scleral transport
. Several factors inuence
the transport of drugs to the posterior ocular segment, such as size, charge and lipophilicity
Chronic disorders aecting the posterior segment require extended treatment duration, and hence, it is desir-
able to develop sustained release systems. Various attempts have been made to improve therapeutic eect of drugs
to the posterior segment, by the use of inserts, implants, micro- and nano-particulate systems, etc.
of these formulations only focused on intravitreal sustained drug release
. However, very few reports were
on subconjunctivally administered sustained release formulations. Sustained drug action in the subconjunctival
space is challenging because of blood and lymphatic clearance mechanisms that wash out drugs
our group has demonstrated sustained duration of action for an anti-glaucoma drug via the sub-conjunctival
route using nanoliposomes
, even though the drug target is in the anterior segment in this case.
Nanocarriers such as liposomes are particularly attractive owing to their biocompatibility, ability to deliver
both hydrophobic and hydrophilic drugs as well as their non-toxic nature. eir size, charge, membrane rigid-
ity and encapsulation eciency are easily tunable. Although it is not trivial to achieve sustained release from
School of Materials Science and Engineering, Nanyang Technological University, Singapore, Singapore.
National Eye Centre, Singapore, Singapore.
Ocular Drug Delivery Group, Singapore Eye Research Institute,
National Healthcare Group Eye Institute, Tan Tock Seng Hospital, Singapore, Singapore.
Correspondence and requests for materials should be addressed to T.T.W. (email: firstname.lastname@example.org)
or S.S.V. (email: email@example.com)
Received: 9 June 2017
Accepted: 13 November 2017
Published: xx xx xxxx