Chemistry for Medicine 1
医用化学１(1st period, Friday)
November 2nd, 2018-

Why size matters? ~ From the anatomic viewpoint

Akihiro Kishimura(Associate Professor,
Katayama Laboratory)
kishimura.akihiro.776@m.kyushu-u.ac.jp

Introduction to Drug Delivery System(from the engineering viewpoint)5

Nov 2ndWhy size matters? ~ From the anatomic viewpoint(人体の構造とサイズ感)6

Nov 9thInteraction of particles and biointerface ~ For control
of cellular uptake (微粒子のバイオ界面との相互作用)7

Nov 16th

Introduction to pharmacokinetics andpharmacodynamics (PK/PD入門)

8

Nov 22th

Formulation design based on nanotechnology (ナノ剤形の設計と疾患治療)

Teaching material：Open access on BookRoll（e-learning system）
教材 - 教材一覧 - Others - 公開資料（岸村顕広）(Contents - List Contents - Others - 公開資料（岸村顕広）)

For students in other campuses
Please e-mail me just after the class including someanswers to the following questions:
Q1. In todayʼs class, what is most impressive or useful
information to you?
Q2. Question or comment:

今日の講義内容で役に立った点、あるいは質問・感想について、必ず何か記載して、講義後速やかにメールで送る。

参考文献『図解で学ぶDDS』(じほう)『人体の正常構造と機能』『ドラッグデリバリーシステム』(日本医事新報)
最先端材料システムOne Point(共立出版)『Introduction to
the Human Body』『生体内薬物送達学』 (基礎生体工学講座)
橋田 充, 高倉 喜信 (著) (産業図書, 1994年)(G.J. Tortora, and
B.H. Derrickson)

Review Article
The journey of a drug-carrier in the body: An anatomo-physiological perspective.
Nicolas Bertrand, Jean-Christophe Leroux, Journal of Controlled Release 161 (2012) 152–163.

5
Brief history of drugs

Ancient Drug

Natural products

HOO

19th Century

H

Extraction of active ingredient
NCH3
HO(Drug was recognized as aMorphinechemical substance.)(M.W.：285)

Later than 19C

Production of drugs by chemical
synthesis; Development of formulation
technology（only small organic compounds)

Current

Bio-pharmaceutics (proteins, DNA/
RNA, etc…)
Pharmacokinetic property is totallydifferent from conventional drugs.

What is drug delivery system (DDS)?
1. Full utilization of highly toxic drug/ Reduction of side effectAnti-cancer drug etc..
→ Difficult to use→ Need to avoid absorption by normal tissue.

2. Overcoming biological barriersProteins and nucleic acids usually undergoes digestion or
clearance from the body. Also, foreign proteins and nucleic
acids often cause immune responses. Also, availability ofwater soluble materials are very low.

→ Need to overcome these biological barriers.

3. Reduction of amount of drugs with high price;
Improvement of quality of life (QOL)
Drug delivery system (DDS) can solve theseissues by controlling amount, timing and location.
- Delivery to the target tissue with properamount at the appropriate time.
“Engineering” greatly contributes to advancement of DDS.

Basic approaches of DDS
a. Control of amount/doseb. Control of locationc. Control of time

1. Controlled release of drug
2. Development of new administrationroute; overcoming absorption barrier.
3. Control of pharmacokinetics / Targeting71. Controlled release of drugs
Therapeutic effect and adverse effect of drug depend on
drug concentration in blood after administration.
intravenous injection

Drug concentration in blood

Normal formulation (oral)
Controlled release formulation
Maximum for toxicity (side eﬀect)

Therapeutic
window
Minimum for therapeutic eﬀect
Time after administration
8

Basic strategy for controlled release
How to avoid “burst release”?
Polymer matrix

Release-regulating membrane
Drug

Matrix type

Membrane type9

2. Development of new administration route &overcoming absorption barrier
Oral admin.
Pulmonary admin.
Nasal admin.
Intraoral/Sublingual
admin.

Depending on administration route,formulation should be designed
carefully.

For systemic distribu'on, use ofblood ﬂow is common route, but
I.v. injection
there are some concerns…
Transdermal✓ Diges'on at stomach and intes'ne
Subcutaneous✓ Diges'on at liver
Intramuscle

Rectaladmin.

Targetsite
Drug administration
Drug absorption
Drug distribution
Drug elimination

Skin barrier
Mucosal barrier✓ Excre'on✓ Adsorp'on onto proteins✓ Immune response✓ Intrinsically less absorbable (watersoluble compound, macromolecules
etc…)
Necessary to overcome theseissues.
10

Drug distribution at the target tissue
After delivery to the target tissue, infiltration to the tissue& internalization into the cells is sometimes required.

CapillaryPlasma protein

Drug

Blood cells

Blood flow

Endothelial cells

Tissue space

Tissue cells

113. Control of pharmacokinetics / Targeting
Pharmacokine'cs:
Determining the fate of substances administered to a livingorganism.
=> Helpful to see “availability of drugs”.

ADME (ADMET)"absorption, distribution, metabolism, and excretion"(sometimes, toxicity)

For efficient delivery of drugs to diseased part,
design of “drug carrier” considering ADME is effective.
-

Chemical modification/conjugation of drugs
Design of new formulation/particles

12Basic concept of drug carriersSide effectNormalorgan/tissue

Insufficienttherapeutic
efficacy

Target site

No sideeffectNormalorgan/tissue

Sufficienttherapeutic
efficacy
Target site
Release- How to deliver drugs
to the target tissue?
- How to enhance
efficacy selectively?

InactivatedDrug

Biologicalbarriers

Escape from
Biologicalbarriers
Drug in carrier

13Outline of the Fate of Nano-capsules
Basically, drugs travel whole body via bloodstream
Typical destination of drugs

Requirements-

Pulmonarycirculation
Systemic
distribution
by blood
circulation

Navigation to the target site
Leakage from bloodstream

Intravenous
injection
Drug-loaded
Nano-capsule(It should be stable& biocompatible)

TargettissueAvoiding
spleenuptakeCaptured byliver and spleenSize < 200 nm

Lunguptake<12µm
Filtered bykidneySize:
100-200 nm

Avoiding liver uptake

M.W. > 30,000
Avoiding renal clearanceFrom the tissue to cells
In some cases, after delivery to the target tissue, proper cellinternalization is essential for woking of drugs.
Targettissue-Nano-capsule
encapsulating
drugs

-

Leaking from the capillary
Tissue penetration

Cell

Avoiding
liver
uptakeNucleus

Avoiding
macrophage uptake

Avoiding
renal
clearance

Proper transportation to thespecific site in the cell isrequired for expression of the
expected function of the drug.

15

16

Drugs v.s. Human body
Drugs ( ~nm)

Human body (~m)
Capillary(~10 µm)

Low MW
compounds

M.W.~500

RNA/DNA~10 nmProteins

They should bearmed tocomplete such ahard & toughmission.

Macrophage(~10 µm)

3. Control of pharmacokinetics / Targeting
For eﬀective targeting…
What can be a target?
-

Tissues / organ…
Malignant tumor, inflammatory part etc.
Receptors, enzymes, antigens, etc. (specific molecules
overexpressed in the diseased part)

Strategies
Active targeting…Direct interaction with molecules of target sites.

Passive targeting …Full utilization of characteristic property of thetissue or diseased part.
e.g.) structure, micro-environment, etc.

Anti-targeting…Blocking delivery or accumulation of drugs in thespecific part of the body, which causes elimination or side effects.

17

DDS based on drug carriers
Design should be performed considering 1.‒3.

Molecular carrier- Low Molecular weight (MW)- Macromolecuels{

Natural: Serum albumin, polysaccharide
Synthetic: Polyethylen glycol (PEG)(PEG; stealth property.)Par'culate carrier- Low MW components:

Liposomes (cell-membrane mimic),
Emulsions, Lipid microspheres- Macromolecular components: Microspheres,

Nano-capsules (micelles, vesicles),Nano-gels

Bio-based carrier
Red blood cells, antibody, viruses, proteins, etc..

18

First of all,letʼs learn about biological barriersfor eﬀective design !!

Biological Barriers: From the viewpoint of immunity
Adaptive immunity

Immunity

Physical Barriers
Epithelial Barrier

Innate immunity

Chemical Barriers
Phagocytes

Epithelial Barrier
１）Physical BarriersIntercellular adhesion, mucosa,（Tight junction, etc.）２）Chemical Barriers- Antibacterial molecules(Lysozyme, antibacterial peptides)- Digestion enzymes
microbemic

mucus layer

Cell-cell adhesion（Tight junction）

antibacterial
peptidesPhagocytes: main component of white blood cells (WBC)
Bone marrow
Bone Peripheral
marrowBlood

TissueNeutrophil: 40-70% of WBC.
Death after phagocytosis orapoptosis

Neutrophil
2-3 h

2-3 dayshematopoietic
stem cell
Monocyte
1-2 days

Ratio

Number of WBC
Neutrophil
Neutrophil
Neutrophil
Eosinophil
Basophil
Monocyte
Lymphocyte

Macrophage

Monocytes: 3-6% of WBC.
Resident in the specifictissues (to form MPS).

months–years

Liver
Spleen/lymph node
CNS
Lung
Peritoneal

cavityConnective tissueBone『免疫学コア講義』(南山堂)Phagocytes:
Mononuclear Phagocyte System (MPS; macrophage etc.), neutrophil, dendritic cell
Phagosome（Phagocytosis by neutrophil）

Internalization

Opsonized particle

Phagolysosome

Binding
neutrophil① Phagocytes can recognize opsonized particles (pathogen
or foreign materials which is bound to compliment proteins)by receptors on their surface.
② Internalization by phagocytosis. (Cell membrane forms a
vesicle “phagosome”.)③ Inner environment of phagosome becomes more acidic,
to form phagolysosome. Pathogens are killed anddestructed. Reactive oxygen species and HOCl
(hypochlorite) are utilized for the destruction of bacteria or
foreign particles.

The journey of a drug-carrier in the body: An anatomo-physiological perspective.
Nicolas Bertrand, Jean-Christophe Leroux, Journal of Controlled Release 161 (2012) 152–163.

push- Total blood flow 5-6 L/min(for an adult man)
- Total blood amount: 5-6 L- Systemic circ. ~90%,
pulmonary (lung) circ. ~10%

Pulmonary
Circulation

Arterial blood: ~20%

Systemic
Circulation

Venous blood: ~80%

3.

an
co
It
m
fo
en

3.1

um
w

Blood vessel and capillary (1)Elastic artery- Three-layered structure- Thick muscle layer

24

Elastic Smoothvasa vasorum lamina
muscle Endothelial cells
Sympathetic nerve
Outer
layer
Middle
2 mm
layer
Inner
layer
30 mm

Lumen

Vein
Outer
layer

- 3-layered, but thin muscle
layer- It has valves to prevent
backward ﬂow of the blood.
=> Skeletal muscle pumping
assists return of the blood tothe heart.

Middle layer

Inner layer
Lumen

Valve

Endothelial
cells
Elastic lamina
Smooth muscle(sparse)25

Blood vessel and capillary (2)Capillary- It doesn’t have three-layered structure.
- Basically, consis'ng of a single layer of endothelial cells + basement membrane
Endothelial cells + pericytes
Fenestrated capillary

Continuous capillary
Pericyte

Endothelial cellFenestration

Conti
Conti
nuou Insulated by nuou
basementssmembrane
capillcapill

5-9 µmArtery1 µm

Vein
Capillary(Radius~3 µm)

Particles with diameter> 1 0 µ m c a n n o t fl o w
through blood capillaries.

Fenestrated capillary
Continuous capillary
Rat pancreas
Two endothelial cells
are tightly connected.
The gap between two
cells is narrow (arrow;~10 nm)Capillary of renal
glomerulus

Fenestration

Pancreatic
islet

Fenestration

Endothelial cells Basement

membrane

Another type:

Discontinuous capillary(large gap between cells)ex.) Sinusoid (found in liver, 30-500 nm gap)

MagnifiedStructure of the capillary wall
Pinocytosis
vesicleCell gap

ChannelLumen
Endothelial cells
Basement membrane

Continuous capillary (muscle, skin, lung)Fenestration
ChannelLumen

Endothelial cells
Basement membrane

Fenestrated capillary (small intestine, kidney)
Lumen

Gap

Channel
内皮細胞
Endothelial cells(No Basement membrane)

Discontinuous capillary (liver, spleen, bone marrow)『生体内薬物送達学』
より

27

Blood Components
Blood cells, proteins, and water
Red Blood Cell
(RBC)

Plasma (55%)
WBC & platelet (< 1%)
RBC (45%)

White
Blood Cell
(WBC)

Platelet

RBC：Size: 7-8 µm, thickness: 2 µm
Platelet：one-third of RBC
WBC：~10 µm. Many variation.

Composition of plasma
Water
Electrolyte
Protein

91%
1%
7%Albumin
Globulin
Fibrinogen

Other organics

1%

Nutrients, wastes, hormones, enzymes etc..

→ Complement protein and antibody recognize foreign substances.

Adsorption of drugs onto proteins
Human Serum Albumin (HSA): MW ~67,000; Most abundant protein inblood (30-45 mg/mL); long plasma half-life (19-22 days); Many
compounds and drugs can be trapped by specific sites (pockets) ofalbumin, particularly acidic drugs.
α1-acidglycoprotein (AGP): MW ~44,000; glycoprotein; plasma conc. =0.5–1.0 mg/mL; relatively long plasma half-life (5 days). Basic drug canbe trapped by this protein.
Site III-

Site I

Site I–II

Site II

Protein-bound drug is notpermeable to cell membrane.
Only non-bound drug is cleared
from blood stream.
Liver proteins and blood cells
adsorb drugs except plasma
proteins.

http://www.abbott.co.jp/medical/product/tdm/topics_1.html

Site II

Site I

Ibuprofen

Warfarin

Phenylbutazone

DiazepamSome binding site of HSA and typical binding drugs

熊本大学薬学部薬剤学分野HPより

30

Protein adsorption onto foreign materials
Human Serum Albumin (HSA): Upon injection of colloidal particles, rapid
and non-specific interactions with albumin occur through ionic andhydrophobic interactions. But, finally, albumin can be easily displaced byother less-abundant proteins with higher affinities.

Lipoprotein & apolipoprotein is lipid

Immunoglobulin (Ig; antibody):transport carrier in the bloodstream.
They can interact with hydrophobic
surface of the material, and navigate it toliver.

These proteins can specificallyrecognize surface epitopes oradsorb through hydrophobic
interactions. IgG recognition
triggers complement activation.

Lipoprotein

Apolipoprotein
70-85%
phospholipid
1%

5-15%

free Cholesterolester
Cholesterolester
Triglyceride
http://www.soarer.hoken.med.yamaguchi-u.ac.jp/Wiki/?
%A5%EA%A5%DD%C3%C1%C7%F2

Very scarce
5-10%
Taken from absolute antibody website

Complement proteins include many kinds of proteins, and plasma
concentration is very high (3 mg/mL), which results in abundantinteractions with foreign materials. Some of them can adsorb on thesurface of foreign materials and pathogens, to trigger the complement
cascades. Complement activation, through the classical, alternativeand lectin pathways, results in enhanced clearance of pathogens via
two mechanisms: A) increased recognition by the MPS throughopsonization and B) direct lysis of the pathogens by the membraneClassical path
Alternative path
Lectin pathattack complex.
Opsonization: Covalentbinding of C3b to the surfaceof pathogens or materials.
The receptor of phagocytes
recognize the C3b, which leadto phagocytosis.

Classical path

Alternative path
Phagocyte
PathogenStrong binding for phagocytosis

Lectin pathC3bC3b receptor

IgG

Fc receptor

Biocompatible surface
To make material surface “not foreign”
Biocompatible polymers

Coagulation factor
pathway

Blood coagulation

Complement
pathway✓ Low immunogenicity✓ Low activation of compliment
system✓ Low protein adsorption✓ Not causing blood coagulation

Clot→Coating or attachment ofhydrophilic and charge neutralpolymer is an effective way.
『バイオマテリアルサイエンス』(東京化学同人)

ExamplesPoly(ethylene glycol) (PEG)O

Poly(2-methyloxazoline)N

Poly(2-(methacryloyloxy)ethyl phosphorylcholine)O

Mimicking cell
membrane lipid.

n

n

n

O

O
O–
O

P
O

O
N+

１ はじめにら，ポリマーベースでの広い用途展開をめざして，非特異

Example: PEGylation
吸着防止ポリマーBlockmasterTMを開発した．

質量解析，DNAシーケンシング等の生体由来物質の分析手法の発展に伴い，近年さまざまなバイオマーカーが２ BlockmasterTMCE化学結合タイプ

発見され，新たなバイオマーカーは抗体医薬などのバイオ
テクノロジー医薬用のコンパニオン診断や分子診断などの磁性粒子表面などの固相表面に抗体を結合する際に新規診断手法の発展に貢献している．さらには，この希分子（タンパク質，核酸）の検出が必要と予想される．希

Dynamic
Pr基を用いて抗体を結合する．一般的には生体由来物質の
ot
motionein
非特異的な吸着が起きないように，抗体の結合後にBSA

少タンパク質，希少細胞の検出に際しては，対象の生体（牛血清アルブミン）などのタンパク質を用いて表面を覆うブ

少な生体由来物質の検出の為，将来は生体由来物質一Protein

は，通常，エポキシや活性化したカルボン酸などの活性High ロッキングと呼ばれる処理を行う．しかし，この方法の場
合 BSAそのものが生体由来の物質であり，品質が安定Plateletのに対して，非特異的に吸着するタンパク質や細胞がノイ
exclusion
ズとして検出の妨げになる．この非特異吸着の低減の要
volume しない． BSE（牛海綿性脳症；狂牛病）などの問題があadsorption
由来物質が抗原抗体反応など特異的反応で検出される

求に答えるため，JSRライフサイエンス社においては，分り，輸出入などの取扱いに注意が必要． 非特異的吸着

離，検出を目的とした，抗体医薬プロセス用粒子，抗体の抑制が十分でない． タンパク質の粒子への吸着によ磁性粒子等の表面に，低非特異吸着な材料によるコーり，凝集が起きる等の問題点があり，代替物質が要望さティングを用いている．一例では，Magnosphere

MSシれていた．BlockmasterTM CEは化学結合タイプのブロッ

リーズは親水化によりタンパク質吸着を低減させており，まキング剤で，図１に示すように，ポリエチレングリコール鎖とた，抗体医薬プロセス用の粒 子AmsphereTMにおいて

N６アミンを持つ化合物である．アミノ基部位を用いて固相 PEO MW

は，Protein A，粒子両方からの非特異吸着を防止する

上のエポキシ，カルボン酸等の官能基と結合し，固相表アプローチが行われている．これらのJSRライフサイエンス

面に親水性を付与，生体由来物質の吸着を防止する役

における知見を応用し，また，粒子をベースとした製品か

割を持つ．

TM

Proteinadsorption

Blockmaster (JSR)
M.W. ~5000.

Prof. Nagasaki (Tsukuba Univ.)

For antifouling.
図１ Blockmaster CE５１０の構造と役割

Lung

Rat lung

Lung has finest capillary, and large and rigid
particles are rapidly trapped upon the firstpassage through the pulmonary circulation.
RBC: High deformability allows rapid passage.
WBC: larger and more rigid; delayed passage.
Rigid particles (> 10 µm): permanently trapped.
Particles (3-6 µm): Initially caught, but finally escape.
Particles (< 3 µm): avoid pulmonary retention.
lungarterylung
vein

Alveolarsac
Alveoli(250-300 µm)

Replica of lung capillary

Blood Filtration by Kidney
糸球体がボウマン嚢に包まれたものを腎小体という。

“Nephron” plays a main role ofkidney function.

Renal
lobe

遠位
尿細管 Nephron

CortexGlomerulus

Renalpyramid

Renal
corpuscle

MedullaRenalpyramid

Tubularreabsorption

collectingductRenal corpuscle・Glomerulus

38

Tubular reabsorption
From renalarteryTo renalvein

Glomerular
capillary(fenestrated)

Endothelial
cells

Podocyte

Mesangium

Podocyte

Urine

Glomerular
capillarylumen

Bowman’s
capsuleGlomerular
capillarylumen

Filtration
Glomerular
capillary(replica; EM image)

Urine

Urine

Glomerularbasement
membraneFiltration apparatus: Three-layered structure
Fenestration of glomerular capillary
Podocyte
Basement membrane

Fenestration

Endothelium fenestration: 50-100 nm, thickglycocalyx layer repel blood cells.
Basement membrane: Network layer of type-IV
collagen; 240-370 nm thick. It contains heparinsulfate with high content, and shows negative
charge.
→ Blocking passage of serum albumin andnegatively-charged solutes.
Slit diaphragm: allows passage of substances< 4-6 nm. Glycocalyx gives negative charges.
Foot process of
podocyte
Slitdiaphragm

Charge-selective &size-selective barrier

Basement membrane

Endothelial cells
Glomerular capillary lumen

Schematic illustration of glomerular ﬁltration apparatus

Urine
Glycocalix
Footprocess of
podocyte

Basement membrane

TypeIV collagen

Endothelial cells

Capillary lumen

Plasmaprotein40

acromolecular polyrived from smooth muscle cells and possess phagocytic properties to
onstrated to trigger
keep the GBM ﬁlter free of debris, as well as secretory functions solinding lectin pathway
cited in case of glomerular injuries [87].
DCs integrating thesemplications of such
For globular
proteins,
4.2. Glomerular
ﬁltration hydrodynamic size < 5-6 nm can be
ed to minimize compassed through. (MW ~ 60,000)
for vaccination purConvective and diffusive forces in the glomerulus capillaries compel
Forpolymers,
arelistedin Table1 the Bowman's
which potentiate
the ﬁltration ofresults
blood solutes
fromthe capillary
lumen toploited to maximize
Quantum< 5.5
nm
can bepassedthrough.
capsule.dots
Structuresof theglomerulus
exert
qualitativeand quantitative

Size-selectivity✓✓✓
controlof
on somewhat is ﬁltered.
Proteins
with hydrodynamic(D )carbonnanotubes
werediameters
confirmed.
✓ Passage
smaller than 5 to 6 nm are freely ﬁltered by the glomerulus, while larger
large
particles
werereported
toequivalentbe passed.
✓ Somesolutes
aregelretained.
For globular
proteins,
this size is
to ainteract with✓
CDCs.
Transportation by transcytosis from capillary side to urine

particulate CDCs enside?
ts with complement
urface epitopes or adough immunoglobusecretion is usuallyrallel, other constitue protein) could playcolloids through reed complement actiacid) (PEG-PDLLA)d β-globulins) or cellles and facilitate theearly kinetic, qualitan interactions shouldrotein adsorption on

H

Table 1
The glomerular ﬁltration cut-offs of different polymers.
PolymerCut-off(kDa)

Charge at
pH 7.4

Biodegradable

Ref.

Pullulan
DextranLinear PEG
PVA
PNIPAM*
PHPMA
Gelatin (alkaline-type, Ip 5.1)

~ 29
~ 29
30
30
32
45
55

0
0
0
0
–
0
–

Yes
Yes
No
No
No
No
Yes

[98]
[98]
[99]
[100]
[23]
[91]
[101]

PEG: poly(ethylene glycol) PVA: poly(vinyl alcohol) PNIPAM: poly(N-isopropylacrylamide)
PHPMA: poly(N-(2-hydroxypropyl)methacrylamide).
*Copolymerized with 5 mol% methacrylic acid to ensure solubility at 37 °C.

The journey of a drug-carrier in the body: An anatomo-physiological perspective.
Nicolas Bertrand, Jean-Christophe Leroux, Journal of Controlled Release 161 (2012) 152–163.

Capture by the Liver42

N. Bertrand, J.-C. Leroux / Journal of Controlled Release 161 (2012) 152–163
Capillary-richorgan; Retention of large amount of blood（~1/4）

nd 60 kDa. The molecular weight limit can beproteins [88]. Grafting polymer chains to drugs
od of circumventing renal ﬁltration and increas89]. Still, today, PEG remains the most frequently
gment the DH of therapeutic molecules [70,90],
polymers [91–93] as well as synthetic linear
ve also been employed for this purpose. Several
non-PEG polymers are currently in preclinicalnt stages. The excretion limits of different macted in Table 1. Macromolecules with sizes situatthreshold, must distort and reptate through the
Front side such
ered. Factors affecting their deformability,
as well as intra-Galland intermoleculararchitecbladdernﬂuence their glomerular ﬁltration [23,96,97].
DCs are toolarge toof
belungﬁlteredwithout
prior
Replicablood
vesseltions include quantum dots, shown to be ﬁlp to 5.5 nm [102,103], and carbon nanotubes
shape of carbon nanotubes might promote
by favourable orientation in the blood ﬂow
ve transcellular transport mechanisms [108].
l studies are still needed to conﬁrm that theiriently fast to prevent accumulation and toxicext. Recently, an interesting study has shown
gium could be targeted by particulate CDCs
~75 nm [109]. Compared to similar particles
zes, colloids of this diameter are small enoughhelial fenestrae and sufﬁciently large to inter-To the heart & pulmonary circulation

The liver engages in numerous metabolic,immunological and endocrine functions. It
receives blood from the gut and the heart via
the portal vein and hepatic artery, respectively.
Blood circulates through a permeable
discontinuous capillary network, (thesinusoids) to reach the central and hepaticveins.

Hepatic lobules
Hexagonal architecture with 0.5-2 mm wide
Hepatic cell plate

endothelial cell
Centralvein

Kupffer cell

Sinusoid
毛細胆管Space of Disse

Sinusoid

To hepaticvein &
inferior vena
cava

From hepatic
artery &portal vein
hepatic
cells

小葉間胆管
小葉間動脈
小葉間門脈

小葉間動脈

小葉間胆管

類洞
Sinusoid✓ Sinusoid: 5 to 10 μm-wide blood vessels having a fenestrated epithelium
without any basal membrane- The gap between endothelial cells: 30-500 nm- Size of fenestration: 100–150 nm

Sinusoid & endothelial cells

44

Pores

Kupffer cell (yellow)

Space ofDisse
hepatic cells

Endothelial cell (pink)
Sinusoid

hepatic cells (orange)

Sieve plate (cluster of fenestra'on)Kupﬀer cells- Macrophages residing in liver.

(80-90% of macrophage in the body is
Kupﬀer cells.)- Phagocytosis occurs afer the mul'valentcontacts of the colloid with themacrophage and spreading of the cell
membrane around the par'cle to engulf it.

Kupffer cell

Liver cell

Liver
Spleen/lymph node
CNS
Kupffer cell

Lung
Peritoneal

cavityConnective tissueBone『免疫学コア講義』(南山堂)Hepatic plasma flow rate

Smallermacromolecules

Glomerular filtration rate

Liver uptake clearance (mL/h)

Positively
chargedmacromol.

InulinMacromol. with slightnegative charge

Rate of fluid endocytosis

Urinary excretion clearance (mL/h)
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Inulin: MW~5,000 (polysaccharide). Completely excreted from kidney.
Standard substance for renal clearance measurement.

account when targeting this pathway. Similarly, the upper size thresholdfor the internalization of colloids via AGPR seems to be situated below
90 nm [157]. This limits the type of CDC which can be delivered throughA lymphaticorgan; filtration of old RBC and foreign
this route.
materials& approach
pathogens.
Anotherconsists of decorating CDCs with hepatocyteArteryopen intargeting lipoproteins either
before administration
or inissitu,
Splenic
red pulp [53,55]
after injection[52,158]. AlthoughSinusoid
cord effective targeting to hepatocytes
splenic cord
can be achieved, the ubiquitous nature of lipoprotein receptors in different tissues can lead to non-speciﬁc distribution and subsequentside-effects [48]. Finally, because non-parenchymal liver cells also
possess physiological and pathological functions, their targetingcanSievingby rodsometimes be desirable. Scavenging receptors can serve to target
cell slit.
Kupffer and endothelial cells [158,159], while coupling vitamin A on
the surface of CDCs revealed an effective way of delivering actives tostellate (Ito) cells that play a fundamental role in liver ﬁbrosis [160].

Sieving through the Spleen

splenic
cord

5.4. Biliary excretion

CentralSplenic
Macrophage
Bile is composed of water, bile acids, cholesterol, phospholipids,
arteryand proteins. Hepatocytes regulate passage from the space of Disse
sinusoid
white
to the bile canaliculi (Fig. 4). Various active transporters are responlooks like apulp
sible for the excretion of small molecules [161] while para- and transSinusoid “slit” of rod
cellular transport is available for high molecular weight compounds[162]. Vesicular-dependent transcytosis occurs either through ﬂuidcells.
Plateletphase or receptor-mediated endocytosis (Fig. 4). The latter pathway either transits to catabolic lysosomes (e.g., AGPR) [163,164] or not (e.g.,
SievedRBC
polymeric IgAs) [162]. Biliary excretion
is
the
only
excretion
pathSplenic
Fig. 5. Structure of the spleen. A. The spleen parenchyma is protected by a ﬁ
way available for non-biodegradable
CDCs with DH larger than 6 nm.
vein
and is composed of the white and red pulps. B. From the trabecular circulatio
Unless they possess chemical moieties that can be recognized byempty into the splenic sinusoids (closed circulation) or directly into thehepatocytes, soluble CDCs must undergo ﬂuid-phase endocytosis to→ Fresh & soft RBCs can pass the sieve,(open circulation). C. Reticular ﬁbres confer a highly-tortuous architectu
transit toward the bile canaliculi [164]. Experiments on isolated perpulp, and blood components must squeeze through the 200-nm wide fene
but old
RBCs
arerigid &of macromolefused&
ratrigid
livers have
shown
thattrapped;
the biliary excretion
sinusoids. The white squares delimit zones zoomed in the following panel.
Rat; SEM(PEG,nm)dextran,inulin andare
proteins)
to be independent
largecules(> 200materials
alsoseems
trappedWBC
image
Rod cellof molecular weight, from 2 to 500 kDa [163,165]. Cationic and anion(endothelilacell) Anatomically, the spleen is coand engulfedmaturation
and recycling.
ic charges onby
themacrophages.
solutes promote and hinder excretion, respectively
細網細胞

Summary of size v.s. systemic circulation
Please remember surface charge, rigidity, and shape etc. areimportant factors as well as size.
Lung capillary>10 µmsplenic
Sinusoid> 200 nmLiverfenestrae>150 nmCell-cell gap ofcontinuous capillary>20 nmGlomerular
filtration>5 nm

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